Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health
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Welcome to the huberman lab podcast, where we discuss science and science space tools for everyday life. I'm ander huberman and am a professor of newbie logy and optimal gy at stanford school of medicine today. My guest is doctor's Susana sobering. Doctor Susan osbert completed her doctoral thesis is work at the center of inflation tion in metabolite m in the center of a physical activity research at the university of copenhagen in denmark. Her research has focused on how deliberate cold exposure and deliberate heat exposure can be used to enhance human metabolism.

SHE is the first author of a seminal study which discovered the minimum thread hold for deliberate heat and deliberate cold exposure, for increasing Brown fat thermo genesis, which is essentially a mood of increasing heat production and metabolic in the body, and for establishing actionable protocols that can be used outside of the laboratory to improve metabolite and human health. Doctor sobs research was published in the journal so reports metabolising twenty twenty one, adding to a long and important history of research focusing on the role of cold and the role of heat in altering various aspects of the bodies, physiology, including hormones, alth, meta lisp and changes in neurotransmitter ors such as dopamine and epa ef. In fact, today's discussion, a doctor sobering, focuses on the role of deliberate heat and deliberate cold exposure on metabolic but IT also includes discussion of the effects of cold and heat on things like neurotransmitter or production, namely dopamine and epa in and nor open eef, the so called catala means, which strongly impact mood and metabolism.

In addition, doctor sob g answers many common questions about deliberate cold and deliberate heat exposure, including, for instance, difference between cold showers versus cold emersion up to the neck versus total body cold emersion, including whether not going back and forth between heat and cold changes, fundamentally, the way that heat and cold impact the metabolism, hormones, neurotransmitter production. And we talk about almost every single nuance and variation on deliberate cold and deliberate heat exposure protocols as IT relates to the underlying science, in particular, how cold receptors at the level of the skin are impacted versus cold reception and perception at the level of the brain, and how all of the impact systems of the brain body relating to mental health, physical health and performance based on her scientific research and academic training, as well as her understanding and use of deliberate heat and deliberate cold exposure protocols, doctor sebert is considered one of the world's leading experts on these topics. In fact, he is the author of a recent book entitled winter, which is, I have to say, a terrific book, because IT breaks down chapter by chapter the different aspects of deliberate heat and deliberate cold into its various constituent part, including cold accommodation, the cold shock response dangers and safety of cold water, the impact of cold and the impact of heat on various aspects of human health, as well as specifics relating to song of versus ice verses called swimming showers at set up.

It's a very throw read and a very easy and accessible read that if you are interested in deliberate colder, deliberate heat exposure or both will allow you to embrace those protocols with the greatest degree of confidence that you're going to obtain the specific and points that you're interested in and to do so safely. Before we begin, I like to emphasize that this podcast is separate from my teaching researchers at stanford. IT is, however, part of my desired effort to bring zero cost to consumer information about science and science of later tools to the general public.

In keeping with that theme, i'd like to thank the sponsors of today's today's epsom is also brought to us by element. Element is an electoral light drink that has everything you need and nothing you don't. That means the exact ratios of electrolier ts are an element and those are sodium, magnesium and plastic um but IT has no sugar.

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I started using the waking up up a few years ago because even though i've been doing regular meditation since my teens and I started doing yoga eja about a decade ago, my dad mentioned to me that he had found an APP turned out to be the waking up APP, which could teach you meditations of different durations, and that had a lot of different types of meditations to place, to bring your body into different states, and that he liked IT very much. So I gave the waking up up a try, and I too found IT to be extremely useful, because sometimes I only have a few minutes to meditate. Other times I have longer to meditate.

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Doctor Susana sebert, welcome. Thank you. So great to have you here. I feel like I should give a little bit of the back story of how we got connected, which was that for many years i've been interested in cold thermo genesis.

IT was the topic of my senior thesis and college, and i've, of course, followed the popularity of wim hf. And we've had doctor crack heller. My colleague from biology department is stanford, who works on cold and its impact on physiology and sports performance.

So for a long time interested in this area. But there's been a real lack of new, let's say, high profile quality scientific information in terms of how, for instance, called lunches and sona, how that impact human physiology. I know there has been some information out there, but it's been sort of scattered.

And then a little over a year ago, I see this paper in sell reports medicine and was immediately struck, at the first of all, the fact that he was in sell reports medicine had been on the sel press editorial board for a long time now. So journals are, of course, for omens journals and the title and the content of the paper was directly online with the sorts of practices that people are very curious about. And they are starting to emerge, things like sona called lunches.

And there was your name first on the author list, and I reach out you through social media. And we've done a little bit of live content. They're together. And i've been tracking what you've bring the world in terms of your book and talking about the result in your manuscript and talking about the science and impact of deliberate cold exposure and sa, and I have to say that it's been a wonderful and remarkable thing to see.

And you're bringing so much quality information about this area that for a long time, I think, was kind of niche and is now becoming more and more mainstream. So i'm going to start off with a thank you for being here, and I thank you for the work that you've done. And i'm looking forward to talking to you about IT today.

So my first question to get things started is what is happening when we get into an uncomfortable ly cold environment. So for instance, if i'm really hard on a hot day, jumping into a cold pool feels really good, but if i'm already kind of, uh, at room temperature, I am a little bit chilly. Getting into that same temperature of water doesn't feel so good, right? There's a shock there. So if you could just walk us through what happens when we get into uncomfortable ly cold water, whether not it's by way of shower or cold plunge at the level of our physiology, and if you'd like our psychology, I think that's a good place for us to start because I think IT will only people to their own experience if they do that. And for those that haven't done IT um might start to peel back some of the the layers as to what the underlying mechanisms of cold are.

Yeah thank you for that question is really good to just address what actually happens in our sociology when we get cold. And you can get cold in many ways. So you can just head out for the one that gives you the most potent stressor, which is submerging in the cool water.

And but you could also go in outside in the cold wind, that's also gonna activate your just sympathetic tic nova system. So get all these new transmitter going in your body. And so your catecholamines, let's just address that. We are taking a cold plunge, for example.

So if you are very hot, for example, before you go into the cold is gonna feel less, is gna feel less stressed? What about the the temperature? A difference from your skin to the cold is definitely gonna give you A A shock, but your core temperature is warmer, and that's gonna feel a little bit bit. So that's why when people go into a song off, for example, and go out and in into the cold water, they, they, they can do IT easily a easier than if they were cold beforehand.

Could I just ask you a few questions? So you mention the sympathetic nerve system, which for people listening who aren't familiar with that is the the branch of our nervous system that's responsible for creating accelerations in heart rate. Um feelings of alertness, it's accompanying with stress.

And the stress response, but it's a company with waking up in the morning for that matter. So it's not always about stress. And then you mention the category means, which um are dupine een f and nor een ephor. So maybe a little bit later, we will talk about those individual or transmitters. But you raise a really important point, which is something I get asked about a lot for people that are curious about using deliberate cold exposure, which is how cold should the water be.

And I know it's very hard to give a straight prescription for that because I think IT boils down to what you just said, which is it's really the difference between your current temperature and really the temperate, the surface of your skin and the temperature of the water. So if you're very warm, getting in the cold feels good. If you're already cold, getting into more cold feels stressful.

Um is there any way that we can start to gage what is the best way to approach a deliberate cold exposure protocol? I mean, should IT feel uncomfortable? And that leads in to the question of how do we baLance the discomfort with the amount of time that we spend in. So for instance, if it's just a little bit uncomfortable with spending more time in the cold, get us the same benefit as getting into very uncomfortable ly cold water for a very short period of time.

Yeah it's really good question and I definitely think that this could be a future studies on this as well to really unravel um what kind of oh are the are the best way or also for which outcomes, of course. So if the temperature is a very cold and you feel that you also feel very cold, and you you should stay in the water a bit long, ger, I think it's just you should get uncomfortable cold. So as long as you get uncomfortable cold, it's cold enough and you get what we call the cold shock. So the coat shocks is activation of your sympathetic nervous system and this activation of the the category mines wish you just mention before.

Does the shock mean that I am having trouble controlling my breathing?

Is that a good gage? Um yeah you can say so because that's kind like how we define IT. So you hyp E A ventilate so you have a faster h breathing rate.

Um so that increases also because you activate your gasping reflects if you are new to this. But if you are adapted, kind of subsides with time, with adaptation. So what you can do is that you can train this cold exposure and you can kind of, I get a debt to IT.

So you don't have this hyper insulating response every time you go out in the cold water. So this is like building up your resilience, building building up your adaptation is going to like this shock, like subside a bit. So it's it's always harder in the beginning, but you should do hard things, right?

Is not something that we you shouldn't think about cold water and cold water emotion as something that is comfortable IT should be hard because that's the point of IT, right? If you enjoy IT yeah then i'm i'm taking something. He's wrong.

It's not right. You should not enjoy IT. Well.

this is an important point you're making because I think that many people shy away from deliberate cold exposure because it's uncomfortable in a way that at least from my experience, is very different than the discomfort exercise because with exercise for instance, um if running hard, you running fast and breathing hard is uncomfortable, but you can slow down or walk.

If um you know lifting weight is uncomfortable, you can remove some weight or reduce the number of repetitions or stop with deliberate cold exposure. I suppose you can be sort of halfway and halfway out of the water or partially underneath the cold shower. But it's very hard to tie trade and adjust the level to it's kind of all or none.

And i've seen um SHE just I can tell this by anecdotally, i've done some work with military special Operations. I won't say which country this was outside the us. Um and these are very tough individuals.

They're used to going without sleep in doing hard, high consequence, highly sk kind of work. And they were asked to do some cold water exposure training. And I was there that day, and I was remarkable about a third of then just went straight in and just kind of drink IT through IT.

You know, they looks to ic, anyway, to me, there were a few wipers, no cries about a third, talked a lot and got, really, you could tell that they were agitated and anxious, but they make through. And then about a third of them just simply wouldn't not get in, pass their knees or fires where IT seemed like they were just dreading the whole experience. Some actually didn't actually go in completely, which was really surprising to me, and that you couldn't tell based on their physical appearance or anything else about them.

They are all high performance as to who would have this response. So IT seems like people vary tremendously in terms of their ability to embrace the discomfort of the cold. Is that from your studies? Is that your experience as well? Or or there these weird mutants who seem to just love going into the cold for the first time.

So some people just feel Better in the cold, and some people are dread the code even more. And you can say, the more people are pushing the code away, they might feel the cold pain even more. So they, they, they would definitely, people who are maybe the soldiers you just talked about, the some of them might be already adapted to the gold cold.

So if they are not scared of the cold, they go out and they embrace the code in a Better way. I could also be that some people have a more sensitive nervous system, and when you are a bit sensitive to the cold, you will, of course, try to get away from IT, right? And you will also have the cold pain more, feel the cold pain more, if they, if, if you avoided. So the more you avoided ded the cold, the the more pay painful IT will feel when you go into IT. So yeah.

you mentioned being outside in A T shirt versus called the version up to the neck versus shower. I think this is something a lot of people wonder about. What are the differences in terms of impact short term and craps, even long term, between cold showers, cold plunge to the neck? So that could be in an ice water or just very cold water immersion with dunking one's head and coming up because obviously, we have to come up for at some point and then simply being outside on a cold day in shorts and A T shirt or something that sort .

so different outcomes um because there they are very different uh exposure of the code to your cold receptors in your skin. So the more you can say you cover your body in the cold, which you will do in cold water, because there are, of course, cover totally, and the molecules are closer to your skin, you will have a more content activation of all your court receptors in the scheme, so that one would definitely activate your enormous envious system more and rapid compared to going out in A T shirt in the cold win. Just go for walk and but that is also something that's gonna activate your super there's nova system, meaning them that you will have an increase in our penetrant uh and you will activate something called uh the the Brown fat so this is a healthy kind of fat tissue that we have in our body and when you activate that, that's gonna increase your metabolism before about .

Brown fat and i'm so glad you brought IT up um because so much to talk about there. Uh what about cold shower? I've been obviously cold showers somewhere in between yeah um being out outside in the air, cold air vers um immersed up to the neck.

If we had more studies on on cold showers, we would learn more about how does that activate on metabolic, how does that increase our new transactions in the brain, which could also have an impact our on our mental baLance. So I think that will be interesting for the future.

Um but what we do know is from from from activating Brown fat and both from road and studies but also in in humans is that as soon as we get cold on our skin, we will activate our Brown fat. So IT is kind of like our first responder in in the body to keep our temperature up. So our muscles is like a second tissue in our body, two tissues which can increase our thermo genesis.

So the fed which is like always like temperature regulating our body and then we have uh the the muscles which will second daily start to shiver and that's going to increase our temperature in the body. But as soon as as you go into a cold shower, you will expect your Brown fat also immediately. So IT could be good also for increasing the tables. M, in theory, because we haven't really any studies showing how much does actually activate the Brown feo. If someone out there wants to do a study, think.

I thought about why there are a fewer studies of cold showers and cold emersion. And I think the answer to my mind is that from a methodological standpoint, is just harder to do. Because if people are getting into cold water up to the neck, they're getting into cold water up to the neck, or as if people are getting into a cold shower, some people are larger, smaller.

Some people are going to stand under the shower with IT hitting their heads, some people back, and then you could direct people to do IT. Yeah, but it's a little bit more difficult also, I think for u uni able research scientists, there's a little bit of a methodology chAllenge that might seem silly to people, but it's a real one, which is if people are in a cold shower also, the water is going to be i'm kind of pushing their clothing against their skin. There's a certain woman and for most people um coming to a laboratory in the first place, let alone being observed while they shower yeah as when you get into call the call emersion you you're getting under the water and know some people might roll their eyes.

And okay, really is that the berry? But science exists in these real world context, and this are very by culture and things that sort. But we run human subjects in my lab until you just the process of getting people to the laboratory and having them park and find the lab and know it's a home new environment with people in lab coats and people moving around and where's the restaurant.

And there's there's a certain amount of stress just associated with taking part in a study for most human subject. So um I totally agree. However, we need more studies of of cold showers.

It's just a harder environment to control in in my in my mind. So IT sounds like any form of cold to the skin that people register as what you call to a cold shock or uncomfortable. Like, like this is kind of daring, activates the Brown fat. Do we know what the pathway is from colder receptors on the skin to the Brown fat? I mean, how does the Brown fat know that we're cold?

Yeah, really good question. And this seems that I I think that, of course, in the future, we will know much more about these pathways. But what we do know is that the coverage sectors will send a signal to our temperature regulating center in in the brains of hythloday us um and that's gonna be um taking in this message and we have so many corporate tors in the skin.

So it's gona be very fast. As you can say, if you emerge the body into cold water, this is gonna to be so rapid uh so I will have a rapid and increase in newer transmitters in the brain to new general a code sol and h which is not that much but but is still there. So you have this increase in uh nor a rinnin, which will then immediately activate the Brown fat because the you can say the activators is the most poor one cold and ordering land and that's going to activate the proof.

But there is also a direct pathway from the corner sectors in the skin to the to the Brown fed, which really is shows that if because of these different pathways, IT shows that that IT could be that this tissue to keep us swarm, or was is developed in in our involvement as humans to keep us swarm and to save us whenever the temperature on our skin very suggest a little bit to keep us in that right homeostatic baLance. So we don't get hypothetic um but also so we don't get hyper thick prety because IT seems that the Brown fed is also activated when we get warm or our skin. So it's also um maybe a temperature regulator in our in our body, but the pathway is different. I think it's also a third pathway from dark tly from the muscles. So the Brown fetch is also exhibited um even though the the most of are starting to shiver so there is an an extra pathway that way to keep our uh our up so muscles and Brown feat are working together to to keep us on so we don't suffer too much in in the cold water.

Super interesting in what I here you pointing to is the existence of three parallel pathways. And this notion of parallel pathways comes up over and over again in biology, as you and I know and and I think it's important for people to know about because um as you said so so eloquently tly the when something is very important to our survival or and or evolution the brain and body installed multiple mechanisms for IT, not just one and and so IT sounds like it's cold skin cold on the skin triggers and a response in hypothalamic then activates Brown fat called receptors in the skin directly to the Brown fat and then shivering in the muscle to the Brown fat um I want to talk about Brown fat in debt and learn from you more about round fat um before that however, I want to ask about shiver um i've heard that shiver causes the release of sucking ate um which then activates the Browns. Fat is IT known.

Whether or not inducing shiver is important and when should people shiver? I mean, i've gotten into call plunges and shivered d while I was in there. And then i've also had the experience of getting into a cold plunge, a cold shower, than getting out when even standing outside on a warm day after swimming pool, and then starting to shiver. So the shiver comes later. So how important shiver and does IT matter when shiver happens?

Yeah, was shivering is is good, because that increases your metabolic and that is going to burn some calories in yoga. You shouldn't be so afraid of shivering, I think, because the shivering, as long as you don't get too hypothermia. So if you don't if you don't sit in the good water for too long. And what you just said by a shivering after you get up, that is because of the after drop. Something called the after drop is when you are called h decreases even after you get out of the cold water. And IT always does that um your body because IT as soon as you get into the cold water h all the your blood vessels is gonna construct because you need to keep your blood in your car and and keep your vital oak and swarm so as soon as you get up that those blood vessels open again and the warm block will flow out and get color and then flow back again into the car. And that's going to decrease the temperature in your core.

of course.

So that's the drop.

So that's the drop. Yeah, glad you explain that. Heard years ago, a wim, I heard him talking about the drop and I heard colleagues, mine, talk about the drop that the first time I i've ever heard explain clear.

Let me, let me make sure I understand that. So I get into cold water. Obviously, i'm cold vessels construct to keep blood near the center.

My body keep me alive. I get out. The warming up of my body allows those vessels and capitalists to dilate. Again, the blood goes out to the surface, but the surface is still cold. And so that blood is cooled and then my core body temperature drops. And that's what you're referring to as the drop and that's what you can do to shiver x and then am I right in thinking that then the shiver activates Brown fat, which then warms me up again? Yes.

got is why you should end on the cold but we can .

get back yeah ending on cold is um you know it's what I referred to as and what has now become known as the sober principal which is um a really important principle about the importance of ending on cold um and not doing what I do which is to get into a hot shower or back in the summer but will get back to in a few minutes so um that's wonderful um that you can explain that so clearly because I think that shiver is something that a lot of people do avoid. People that go I don't want to you know the chattering and the teeth then and IT IT feels like a loss of battery control, which really IT is its its in autonomic response .

yeah but I don't think that people should should avoid IT that much is just like seeing shivering as a way of your body in in like it's training. It's training for your for yourselves, is training for your muscles, is training of your metabolism. And that's going to increase.

You was called the insulin sensitivity. So if you can, like in your mind, get used to the thought of shivering. Is just like when you go exercising in the training center and get their feeling of like of this is tough.

Now IT hurts a little bit. Yes, it's gonna hurt because that's what shivering ing also does is, but it's just a different way of training yourself. Ells in your body. It's gonna create what is healthy stress is called homeless in the cells. And the more you expose your your muscle cells or your Brown t cells to this kind of like healthy stresses, exercise, heat exposure, it's going to make them Better add like activating and also at keeping you healthy.

So as long as the cells get exposed to this is it's gonna keep them on its toes, you can say, because IT becomes more robust, increasing these heat shock proteins and culture p proteins in the cells to make you more robust for the next time. And that is also what happens when you go to the training center. And I keep like to drawing that parallel because people today know more about we know more about exercise and what that uh is going to do to your muscle cells and and but the same kind of like training is also what you do when you go out and into the code and submerged into code because that is just your cold training center. You can say that and and also your heat training center going into the snow because the cells are getting stronger with hermetic stress. So it's the same process, just different places.

I'm so glad that you brought up the fact that the discomfort or the embarrassment or both of shiver is still crucial to um actually to reach for and try and experience the same way that with exercise. I think a lot of people don't realize this, but when we did our series with doctor and galpin, we became clear to me what should have already been clear to me.

And I think that most people don't realize, which is that if we were to measure heart rate, blood pressure, stress hormones and inflation tion in a human being during exercise, IT IT would look as if they were ready to die. Blood pressure would be high. Inflation tion is through the roof, but all of that is setting in motion and adaptation, or set of adaptations that allow blood pressure to be lower at rest, that allow inflation tion markers to be lower at rest.

All the things that everybody is seeking with exercise in in addition to, of course, the aesthetic changes that people are seeking with exercise, sounds like the exacting things are happening with the code. So um the redundant message here seems to be that the more discomfort provided is done safely, just like with exercise, the more shivering, the um the more cold shock provided is not to the extreme and stop somebody y's heart right we can talk about thread holds for that a bit later IT sounds like all of that is going to set in emotion. Some long term changes that will make people feel Better and will improve health.

Could you just touch on a few of the longer term changes that are known to occur? I mean, i'm well aware of the study showing that H I think was european journal physiology IT was uh the eupeptic ourn's physiology showing long lasting increases in categories dop, np and f edf. For many hours after delivered cold exposure. What are some of the other things that happened at the level of metabolic and ground fat? And let's say, the hours and day after a deliberate cold exposure.

as soon as you go in, of course, there's an activation. But this seems like, no, you're asking for the the leader outcomes like blood stuff like that.

You mean yeah blood pressure but also in terms of metabolic, I know that you know in your study you should and will talk about Brown fat in depth here in a moment, but that there were changes to the Brown fat that equate to changes in, for instance, people's ability to be comfortable in colder environments when they're not doing deliberate cold exposure yes or in the same way that I can um exercise. On an exercised bike or goal for a hard run. But then if I go hiking with the family on sunday and what's a steep climb, I could do that steep limb more easily, because I called fit as a consequences. The of the exercise, what are what are some of the fitness adaptations of deliberate cold exposure?

Yeah so what happens is that you you get adapted a little bit every time you go. So you will, like exercise, get labor stronger. So every time you go into the cold water for every time, you will be more exposed to you, you feel more comfortable in the code.

So you ona, you're gonna d your adaptation, which happens on a meta lic level, gonna the Brown fat. So we have more exhibition of your Brown fat. The my cona in the the Brown fed sales are gonna be you have more of those and there will be more efficient at heading you up because IT expects the body expects you to to do this again. So you are prepared in a way the cap illness in your skin is also a will also become Better at like constricting, so you will have a Better shield of your body to a prepare you for the next time, so we will become Better at h going into the cold water in that way.

So the the body makes this mechanism to changes your body in a way so you can expose yourself for the next time, right and and also you will have also your um stress response will also be subsided a bit so you have a less increase of your catecholamines um with time with time also you have because of this activation of your Brown fat or your muscles, you haven't increased in uh in in your metabolite, which will then h make your insulin sensitivity a Better and this is shown in in studies for example there was just interesting study I found just before I I started my PHD which was from give her stormer um IT l from two thousand and sixteen where they measured a metaphysical not in, not on Brown fat, but they measure insulin sensitivity in middle age men and women h during one winter swimming season. So they were not very Young like they were in my study, but they they were middle age. And I think this is very interesting.

So they during these four, five months, they were went to swimming. They saw that they had a lower block pressure after the season and they had a lower heart rate. And they also so that they have a Better instance sensitivity.

And I think that is very interesting because if you can have a Better insulation activity, you can prevent lifestyle thesis. So um and we lower road pressure, which is a very strong outcome also for selling how much inflation tion who have the body. And because that I didn't measure uh Brown fat, I figured that I could be that was the missing link that was one of the explanations to why we see this less inflation tion in the body.

So um the longer outcomes so the longer m outcomes could be that you lower your blood pressure and have a lower heart rate. You also um have a Better interest sensitivity and a Better lucas baLance. But that was shown that was shown in my study.

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Um you know, blood pressure, of course, most people are aware of blood pressure. And what IT is is what I measure when we go to the doctor. And it's not very sexy nowadays. D, D, blood pressure, it's if you wants to hear about the inflammatory and the microbiome and all of that stuff is really interesting, but I think that blood pressure doesn't get enough attention. Um and we have spoken to on this podcast to dr.

Peter attia who is an expert in longevity and health span and things that sort and I was surprised to learn, again, I shouldn't been surprised that the number one reason people die worldwide is three able vascular disease and cardiovascular disease. And they're easily three things on the list of things to address. One is not smoking or raping, by the way. Not there are a few other things relate to blood markers. Apple be in things that sort, but then the big one is blood pressure.

And so it's it's interesting because we don't think about blood pressure that much in any more um as as the kind of people in health optimization and health, but blood pressure is so vital to control so it's wonderful to hear that deliberate cold exposure is one way to control blood pressure, I am guessing in concert with other forms of exercise. yes. Um let's talk about Brown fat and um if if you're willing i'd love to drill into Brown fat at at a deep level um again, my understanding this is is far more elementary than yours.

Obviously you're the expert misunderstanding about round fat is that it's located in specific areas of our body um maybe more widespread than when I learned in school I thought I was I was thought I was just at the clouds in the back, the neck and utter back. But who knows I learned that there's more of IT when we're children, maybe more distributed throughout our body and that is rich in metal contra. But what is so special about the Brown fat? Like if we could just go into the biology Brown that a little bit.

What does that look like? You've measured IT in human subjects. Where's IT distributed really. Can I expand its distribution? Can we activate and expand the amount of Brown fat as adults and um for those of you that are crunching already thinking we're talking about getting fatter, it's quite the opposite. We're talking about not subcutaneous fat but fat located around the the organs but please educate me um tell me where i'm wrong and expand my ology on .

Brown fat okay yeah you are not wrong. But um it's not true that they are more locations of the Brown fat than we previously thought. Um there's this very nice study from two thousand and and seventeen by lighter l where they had made these empties overlays of there are subjects where you can see where in the body do we have Brown fat and where can we grow more Brown fat um so to say um so the Brown fat is is very plastic so that means that they can he can grow decrease and this is proven in in studies where we have seen people with the fail co citta is like a very specific control type.

Where where from the seventies, where we can see that if they have this specific kind of a cancer type, they have they have this tumor on the a general gland, so they have like an a huge increase in or adjournment. And because of that, they have this continuous activation of the Brown fat. And they have grown a lot of Brown fat in whole body, a acoming of where it's located, these six different places.

But IT is less like very much comparative, like Normal people and and what they then see what we learn from this study is that Brown fed can parents grow if you have um an increase in nat in the body? It's not like you want that because when that happens, you have a high blood pressure. You don't want a chronic, right? You just want IT on like a short amount of time and then you can grow a bit, but you don't want a chunk, of course not, but because IT IT exhibits also your sympathetic tic.

Nm, so they have also showed they have high blood pressure. They had, they lost a lot of weight, of course, because this is activating your metabolic. So they they found, luckily, that when they h remove this be a tumor h that uh the Brown fat um decreases again to Normal size and they can wait again, and they had Normal blood pressure.

So the story as well. But IT is kind of like proof concept of the Brown fat can actually grow. So it's plastic in its in its way of like you can IT grow and I can decrease again.

So that's very good, good studies to to see what what the body is capable of. But we don't, of course, one, all that Brown fat we just wanted to be just want to keep IT actually and keep IT activated. Because what we see in studies is also that after the age of forty and people, uh, the studies have shown that there is an association with having less Brown fat but increased obesity.

So of course, we don't know yet whether Brown fat decreases with age and therefore we get obese or we get obese and therefore we have less Brown fat. But as Brown fat is an instant sensitive organ in our body and we get obese, h just like the muscles get less sensitive, instant sensitive, the Brown fed us as well. And therefore IT may be decreases. IT could be a theory is that I think could be one of the reasons why we don't see that much Brownfield in elderly people. Some have a lot, basically people working outside there are .

still showing this who people who I do physical work outside. Farmers, yeah interest .

keep in.

And I suppose we should clarify for people and kisses don't know that insuing sensitivity is a very good thing. You want that you want yourself to be sensitive to insulin insensitivity is type two diabetes um and is associated with obesity um so just point of clarification there. Ah yeah it's interesting to me.

I usually work out at home, but I I go to the gym once or twice a week if I can because it's good if I see the outside world. And there are a few individuals at the the gym who are they're not particularly large r or moscow um but they're incredibly. Um lean and their posture is great presently from the moscow skills to work um and they there in their seventies and a bs I mean it's remarkable right and and I know all the tell tale science of mono augmentation.

I'm very good at spotted that there. If you tell tel signs of talk about this another, they're not that's not why there their they're fit. They're clearly of that look and you see this for outside the gym too. Of course, for people that look like they've done a lot of physical labor their whole life, yeah, they're just moving a lot that they have strong hands and features and their they're not necessarily excessively leaning, but you can tell that they're been using their moscow alto system.

And i'd like to talk to these people and ask them like not what are you doing now for your workout, but what what did you grow up doing, you know? And I would say, and obviously haven't run statistics on this, but more than seventy five percent of them respond that they grow up on a farm or that they did some sort of manual labor, or were a postmen or a postwoman, or doing something where they moved a lot for their early years and throughout middle age. And most of them are now in retirement, but some of them are still working, and they all still moving a lot.

So the relationship between shiver and Brown fat make sense to me ah but is that the case that as we're just moving around and I heard of neat non exercise these tera genois so we're just moving around um that we are activating ground fat? Or does there need to be this dresser? Does there need to be shiver and a cold stimulus or heat stimulus to activate the Brown fat? In other words, um is just staying active enough or do we need to do some sort of shock type thing like deliberate cold exposure?

Yeah I think that is a really good Christian. Because how how also why do we have this tissue then? If if if IT has to be extreme, then you can question what what do we need this tissue? But IT seems that you can activate the Brown fed was just a little bit of exposure to to coat the coalition of the most potent stress, our activators of our Brown fat, because it's our temperature regulating organ in our bodies of first responder to that.

So the muscles will be a bit too late. And therefore, we have maybe these two kind of tissues. So actually just exposing yourself a hand, actually just to cold water, the studies have shown, and that if you just put your hand in cold water and not that you're going to gonna do that all day or or every day or anything, it's not it's not something you have to do, but IT just shows that you can activate your prompt just by getting a temperature change on your skin so you can go outside.

And t shirt, that's why also, we were just talking about, well, people who works outside or move a lot or get out in and out of like changing the temperature of their body all the time, they will have more Brown fat. And h activating, that is gonna keep your metabolic higher and your insulation sitivation study have also shown that so the Brown fat can be activated as soon as you would just change your temperature, the skin so going outside in A T shirt wearing cooling vests also studies have shown this for ten days. It's gonna also a grow your uh your Brown fed so you can get more Brown fed if you expose yourself to the you don't have to start a cold uh shower.

You don't have to start in a cold plunge if you're not really ready for that yet. But just exposing yourself to coin has also shown to activate your ground fed or if you don't want to be like in uh awake state, uh then you can also you sleep in the cold and you won't notice that that much maybe. But studies are showing that if you sleep in nineteen degree's cells and then you will activate your Brown fat and you will grow your ground fat.

So you have more of IT. So this very nice studies from hand from two thousand and seventeen in showed that uh a group of subjects who slept t in a roomed twenty four degrees and then they made this p city scanners to see how much Brown fat do they have from the beginnings。 So what we call baseline then they measured again after um a month of sleeping in ninety degrees and they saw I think is remarkable, just one month at nine degrees sleeping there. They had a debt on and they will still had close on when were sleeping. So they are under .

a cover here under under ah yes.

this subjects will sleep in a ninety degree for one month had increased as inland sensitivity. The next month they step at twenty four degrees. They measured this again and then they had decreased actually a little bit and then they stepped at its twenty seven degrees so quite warm room actually for for the fourth months um and they saw even less activation of the Brown and also influence sensitivity.

So IT seems that you can expose yourself and pretty rapidly the Brown fed will respond to this because it's so sensitive to no adrenal, right? So if you keep exposing yourself to a little bit of cold, you also get a little bit adapted to IT. But that's because the Brown fat and has grown these more, my country a in the cells.

So these small energy fabric steps gonna activate the cells, and that's gonna take up glue cose and fat from the fatty assets from the bloodstream to keep the thema genesis oc. And that's gonna clear up some sugar, and it's gonna clear h. So the blood stream and some fat as well.

So the Brown fat can in that way decrease our unhealthy fat, which is the ite fat um and the White fat is what we don't want too much off, but we still need some, of course, and it's our energy storage. So it's very important that is there which you don't need A A lot of IT. So on our size and also around our inner organs that swear it's located.

So if we can have exhibition of the Brown fed just by going out in the cold and just by sleeping in the cold room, or if you are have courage for IT, you can go out and expose yourself in a cold lunch. Cold showers is also gone to do the trick, so you can do different variations of this. Just explosion yourself to various temperatures. Is going na activate the Brown fed because IT was involved to keep us in a perfect homeostatic baLance regarding temperature. So to keep us alive, incredible.

And I just get a clarification around this ninety degree sales um room that they're sleeping and so they're under a comforter dev and um and you mentioned they had close on the room is one thousand nine degrees sales, but the temperature under neath their blanket might not be nineteen grees cells. So presubscribed ld on their face that's activating a the the increase in Brown fat that was observed. Is that is that a reasonable expectation?

I I think so yeah because it's you have so many cover sectors in your face. Uh so it's actually it's enough and think correspond es very well with the studies showing that you can achivi the Brown feat just by putting a hand into A A pocket of coat water. And I did this experiment myself in in my studies, just to see how well did they h respond to cold water.

So IT was a four degrees sales cold water for a four minutes. And then I just messed red block question heart right to see, do they have like an activation of this? I actually also measured the round fat during this, uh, code explosion for phone minutes with an infected demography camera to see, can I see that the Brown fed is activated and just just to, uh, go back to the location of the Brown fed.

So usually you cannot really see activation of your problem if is locate a sensually in your around your sensor nova system um and and the biggest depot assurance before is up here under the the collision collar bones so um and very close to the skin surface and because it's so close to the skin surface, I could measure IT with this very expensive camera. You and it's not very feasible for people to go home and do this don't because IT takes a lot of practice, I can tell. But we measured the Brown fat with this and and I could see that after a few minutes, that activation was there, an increase in temperature, a rules from that activation, just four minutes.

So it's very rapid. And i'm also missed red in my study. How deep was the Brown fat under your skin? So it's very close to the surface, which also shows that IT IT needs to be there to hit you up and hit your in organs.

Well, i'm delighted to hear all of this, and i'll i'll tell you why. One is by wave anecdote. I mention a little bit earlier that as an undergraduate, I worked in a lab that stayed through magius and we were doing that in animals.

But we had this room that was very cold. The whole room was called the guy who I worked for at the time. I am hurry car loves of very accomplished physiologist. He came from this lining age.

I don't know if this literature still um discussed much but it's a beautiful literature um from rothwell and stock they were the ones who discovered um non exercise induce thermogenesis the fact of people bounce, who bounced their legs a lot and move around a lot and have a lot of kind of sarcastic movement burn up to eighteen one thousand eight hundred calories more per day than people who sit more still credible just incredible um I don't think that work desert gets as much attention as as IT deserves publishing journals like nature so very a fine journals but in any event uh one of the things that I notified when I start working in that laboratory was that I was cold because the room was called and doctor carl l Harry um said, well the key is to wear A T shirt in here for about two three days and then you will call adapt I thought, wouldn't I want to put on a hood and get warm in there so I was comfortable he said, no actually what you want to do is get yourself uncomfortable ly called. Activate your Brown fat and indeed, when I did that I think was just two days of being in that cold environment. Then I could come back on the third day and be perfectly comfortable because the Brown fat had expanded um or were added midco o or both and I was perfectly comfortable in that environment.

I also got very, very leaned in, in those days and weeks now, I i've never been somebody who is very lean, nor my somebody who Carries a lot of access to oppose issue. I kind of somewhere in the middle. I'm sure I could adjust that with feeding if I want to but I was I was striking, uh what a powerful effect IT had on my entire system of thermal regulation.

And one of the things that I also delighted in when sell reports um medicine published your study as they had an accompany um press release that went out to to those of us that receive press releases and IT described A A saying in scanner avia which is essentially i'm not going to attempt to uh speak a danish even though I have much of my family is in denmark I believe when I from denmark with a lot of gains in my family um I won't embarrass myself by trying to speak daish as I did before the microphones were rolling but um what that there's a saying that I think essentially a translate to in the fall when when you're approaching winter, you want to actually wear fewer layers, not bundled up when you go outside, so that you can prepare yourself for the cold of winter and be able to heat yourself up using your ground fat and that in the spring, as the temperatures are warming, rather than removing layers, you want to wear more layers in order to be a little bit uncomfortably warm, so that in the heat of the summer you're Better at cooling your body. Do I have that right? And maybe do you know the saying and would you be willing to share you only the sweet endings will be able to understand maybe the most regions too, if you don't know if that's okay?

yeah. So I know I know the concept of IT because we say you should you should wear less before winter and and more before the summer.

And so doesn't have to be a yeah and and you're .

completely right. And I think this is this is just something that we know in the scandinavian countries. I think that we, we, we intrusively know this.

But if we just go back a little bit in history, I think that um around the one thousand nine hundred fifties at the russian government went out and said, well, we should do something about the took tobacco sis pendered uh epidemic worse at that this time. So they they wanted to have the people and be more resilient, ent to the cold, and also increase our union system. So in scanavius, and actually also russia, we put our babies outside to sleep a in the problem.

And that is like to h also to to get more resistant to the code, but also to increase our immune system. And we still do that. And then, mark, so we do.

You really? Yeah, we do. Babies are taken out in the cold.

in the snow, in frosty rain, everything. My two boys have been sleeping out in winter of at least the the first many three for five years because it's like very good for them and they get uh a Better immune system and get resilient to the code so they will have less codes. And also they run around in A T shirt when it's super cold because they have activated all the Brown fight.

I didn't understand at that time, I I must say. But I can like intuitively also new, because we have inherit this a way of doing things with our culture. So, and I have heard people coming from the U.

S. And a dance are crazy. They put their babies outside and problems and leave them there, the legal inside and drink coffee .

on the well, I don't think games are crazy. I I I adore the dames. Um there are amazing uh, culture and people.

I'm so fortunately to have family members from denmark, but I didn't notice. So when when we were in copenhagen, I know um we we saw you there. Um uh, not long ago that was june.

Um the water in the harbor was was cold for even though the pacific is close to hear, which is very cold, not pretty cold. But I IT was summer time a ish. Um so people were in summer time mode, right t shirts and shorts and things that that sort. But IT did strike me that people in copenhagen are dramatically fitter than they are in the united states.

I mean, first, while everyone is bicycling everywhere, yeah not many people wearing sunglasses so trying to extract as much photo on energy from the sun as possible which I support uh as everyone knows that a big fan of getting sun but also um when we did see swimmers um they were swimming in this cold water and like I was nothing and there the range age of the swimmers what was remarkable, you saw that kind of fit try athlete looking types, but also Young kids. I really Young kids and then people probably in there again there their seventies, eighties, maybe even nineties, really remarkable, vastly different than what you see if you go to the ocean here in los Angeles, cern or elsewhere. So um yeah your skin nans are on to something.

With this, i'd like to talk about your study. If you could give a solo bit of the backdrop about what motivated that study and then and then walk us through what you did you know who the subjects were um what you had them do, what you measured in as much detail as you would like to share because I think it's such an important you know even I unfair to say landmark study because IT also explored not just cold but sona and the the coal use of cold and sona as a way to probe metals listed and Brown fat and other markers as well. And as you do this, uh, i'm hoping at some point that you might tell us some of the observations that you might have made that interested you that perhaps were not in the paper because that's one of the great benefits of sitting across from somebody who who did the work in detail. So yes, you can tell us about your study um and what you did and what you discovered.

Thank you for that question, Andrew. I I love to like also explaining about what did we do because when people read this kind of paper, they just see the numbers. They don't see what what happened before that.

And human studies are very different from from my study. My study, you can do a knock out of something and then everything is like perfectly matched and controlled. Doing human studies is very far different from that because people are different even in the groups. So yeah, but what we when I started this research, two thousand and sixteen, I did not really know what the Brown fat was. So I started reading up on all this, and I was very interest in preventive medicine.

Also, the studies that I did before the Brown fed was also like very much in in the province side, like, how can we that was about something else, the sweet tooth, and how can we lower our sweet tooth and stuff like that? So, but after that, I wanted to do something new. So I look into the road.

Fat got higher in this fantastic research group, where they is a cell group. So they mostly did cell studies, and they didn't have anyone to do a human study yet. And but they really wanted me to to do that. So I writ upon a lot of research about how does the ground fact get activated, what have been done already and I mentioned the paper before with steeping in the cold.

I found that particularly paper very fascinating and that was also where um at that time as like, okay, so cold exposure as an intervention of sleeping in the cold could be a good thing to go out and say, well, people do this but on the other hand is first of all, he was already done that was one thing but the other thing was like, well, I wanted to see if we can do and like some kind of activity so we can have people move also go or do something, do something together or whatever and and the cold, uh, made us think about what what about winter swimming? And IT was kind of like a bit of a joke in the beginning as I went to swimming. Yes, gna activate the Brown fed ride.

But but when we read the digital, we couldn't really find anything about activation of the Brown fat with cold water, besides hand in a bucket of cold water that there was already there. So we were just you. Okay, so you should be very poor. And exhibition of the Brown fit if it's cold water, but very different from cold air. So IT was kind of also a new thing we were going into, and we knew that we were gonna do like and more of a proof of concept study at the beginning of ed because I was like winter swimmers, um most in theory, activate the Brown fat, right? But we cannot didn't really know which was this kind of stressful, too much, too little or what would happen actually.

But we had this idea about, well, we always say that cold water and winter swimming activity omega blister but but do we know if I did does that no we don't so um and while this I tea was a little bit fun fun at the beginning, um we kind of accepted they was like, okay, let's just try this out but because we didn't have the funding for IT, he was like, okay, let's do a proof concept study um let's go with a small number but enough to see um a difference between the groups. So the power calculation of that study is done on what we know from pity scanners of the Brown fed. So that's the main outcome of that, of course.

So um and we wanted to go a little bit small and the numbers of of participants because we wanted to digg a little bit deeper into the different mechanisms. And also we do some of the the the days. So I really wanted to do that to see if I can recall, ade, also the findings.

And that's gonna take a lot of a lot of funding, but it's also gonna take a lot of time to do IT. And so the proof concept was just going small. But looking at different mechanism s we also took um fed biopsies, for example and looked at the White fatto see if there was any differences between the groups before and after engh that so that kind of like how is started.

And then the first year was like a field study for me. So I was not a win to swimming when I started this. I was just really, no, I wasn't at all.

I was say I was a bit RAID of the code myself, bit of a coat. Sisi, always cold, having big socks on and sweeter and stuff like that, just like, I am so comfortable. I'm just like everybody else, very comfortable.

I like being completely temperature neutral. But I started like playing with this story like, well, if this is so healthy, in theory, I should not pack myself up. I should start not doing that.

Yeah, but the first year observation of winter swim is under tty. They kind of joked about as they come on as, and you need to try this. You cannot study this unless you have tried.

And I was like, haha, very funny. Of course I can do that, but I couldn't. I I read the lady to, I understood in theory what happens when you go into cold water.

But I completely understood. And when I first tried IT the first few times, not so funny, i'd felt painful. I was just like running too long after a long break, and you and your muscles heard the day after, right? You completely regret that you took that extra mile.

What about when you say uncomfortable? You mean uncomfortable when you got in and when you were in or uncomfortable afterwards because I find that um on rare occasions but I should just full disclosure. I I do deliberate cold exposure every morning for about a minute to two minutes in a cold plunge.

There are days that I miss, but when I met home, I do that. And when I travel I do a cold shower. I do finish with a warm shower.

So when we talk about why, that's probably not the best idea. But um and i've been doing IT for some years now um on and off. But so just full disclosure.

I'm a devote and I have family members that hate the the cold, but i've gotten into IT and are starting like IT, but they don't and I don't necessarily like the experience in the cold water, but I love the way I feel when I get out. And I am one hundred percent on that statement about loving IT. When I get out occasionally, IT feels good to be in there and feels and I think i've learned to control the gas reflex and the hyperventilation. And I just have told myself what we know, which is that the forebrain struggles to engage for the first twenty or thirty seconds but if you can get past that wall, it's far easier to push through. Um but when you say that he was really uncomfortable, do you mean the experience of getting in or you also felt lousy afterward?

Yeah it's and very important to clear that out. I only felt very uncomfortable doing IT at the moment but afterwards the first time I went with with the group and actually my husband was as as well because I really wanted someone I knew um coming along because it's very Normal if you haven't done this before, you feel a little bit anxious about IT, didn't this is just an studies as well because blood pressure, how right goes up in in those who are new to this kind of activity? So I was a little bit anxious about IT.

So I was really uncomfortable just doing a good afterwards. As soon as I got up, I felt fantastic. And we went into the sooner and I did three rounds because I just laughed. I love the feeling afterwards because you have all this new transmitters going on your brain and you feel more positive.

You feel, I feel, immigrate to have so much energy, and that, like I, I could totally see why people would do this to get energy throughout the day, because I definitely had that. I didn't have to do three dips to to get that. I think one would be enough, and I often do that also.

Now today I do one dip, sometimes I do two. A fee dips um in in one round you can see one day, but often is like just one or two times a week for me. That is enough to to get that energy and to get that positive feeling.

And I think that that is also why I I put up my study in that way. I wanted to study the lowest dose. You can see the lowest amount that we can get away with, but still see.

And health benefits. So what I observed there on the jetty was that something did IT a long time. They were in the water for very long time. And so may seem maybe a little extreme.

Could you an example of a long time?

Well, so maybe they were like, really swimming and they could beat twenty minutes of half a long time. And there was like, ice and people who came up. I mean, I just didn't really feel that this is a something that I wanted to go out and recommend .

to people search subject in either guess if you're not adapted, I mean that people you know people can do that also a twenty minute called power or twenty minute cold plunge. I know people do IT, but it's probably not a good idea.

No, probably not. It's going to exhaust yourselves and they will make them age too fast. So exactly that's uh when you pass that homework, stress is the healthy stress level. That's what is happening. The quite opposite is, is almost chronic stress actually in the cells.

Well, what happened then was that um I found out if if I want to have this protocol get through ethical committee, I I really needed to go like very like sleep with the not too long and and make sure that they were also very healthy and and to get approval, of course, of this study. But what I did was to to recruit winter swimmer who already have been swimming for two or three seasons, and I just observed them. I said, i'm not gonna do an intervention study yet.

I did that after, but I I wanted to do like a proof concept where they were already adapted to the cold, and then compare them to a match control group who were matched on, and you can say, diet. So where are the vegetarian or not? And one of them were in each group.

they no.

no mazing .

and are amazing. And vegetables arians, each .

group OK.

And they were made in vegetable. An, I have family members of vegetation. An, so i'm just poking for.

yeah. But they were matched on different things. So what we usually match, ched, the mono social. B. M.

I, we shows one gender in this study, and we would always choose both men and women Normally. But we do see that there are different Brown fat levels. H depending on gender. So women have more Brown fat than men.

Yeah, interesting.

Yeah, I think is interesting.

Deserves study.

yeah. yeah. why? Actually I think it's interesting because women are also smaller so in size mass, right but they also have um a lower pari fil temperature, especially on hands and ears.

And is that right that's documented .

that women do .

run colder than men no no, no we we won't to the psychological yeah something .

else as a .

different podcast yes.

I know the time. So women are just colder physically. H so on hands and ears, it's mesut on that and and and feet as well.

So compared to men, and men have bigger hearts than women, and they can pump out more lot perf than in a woman's body. So there could be an explanation for the colder hands. For sema comfortable state is also different between generous. So men are more comfortable at twenty two degrees is, and women are thermal comfortable at twenty four degrees. Sales.

and this is the thermos wars of home, have been now validated.

Yes there a two .

derec IT by the way, prior to um starting recording, uh I made the executive decision that we are going to go with salcido throughout the podcast um because the majority of the world uses selsea. So for those of you that think in fair and height, um the internet is your friend in making those conversions, but we're sticking with sales. So men tend to be thermo comfortable at twenty two degree celsius, women at twenty four OK.

Interesting explains a lot about like also some arguments in the homes where men are turning down the heater and women are up the header and they cannot really so it's it's really i'm on both sides here understand the men. We understand the women, but it's there is a difference there, which was also one of the reasons why we would have we in this proof concept study shows one gender. So IT was not like only because we wanted to study men.

He was just to see to eliminate h or the factors which could have an impact on on our results. So um that was one of the reasons, but also because we yeah so women have have more Brown fat than men othe wise we would have to like to four groups or something like that and not having funding yet. We were like, okay, we need to do like we just one a group, just a control group and then and a group who will all way to winter.

So I recruit when to swimmer who have been swim for two to three seasons, because I wanted them to be already adapted, but not going too long in the water. So they told me, H, I did a lot of screening here, of course, beforehand, and interviews to see, to ask them, how much do you do and um how much do you? How long to stand the water? And I monitored, how long did they? Instead, what I recruit.

Based on that, they only theyd like two to three times per week. IT seems reasonable for for denmark at least, to do that. And they stayed only in the water for one to two minutes.

So the cost subsides very quickly. And you would get this activation of your rest and digest system, which is your paris pade nervous system. So the other branch of your nous nervous system, and you get that exhibition because you submerged into cold water.

And when you do that, you have an activation of your diving response. And that's gonna slow down the, you can say, the, the, the consumption of oxygen also in your body. And that's gonna low down your heart. red.

Could I pause you on this? Because i've heard this before, that when we get into cold water shower or emersion, we get this sympathetic atomic response. So increased blood pressure, increase heart rate, release of north and after an from the local st. Rulest in the brain, release of a journal, doping, a general from the, from the generals, doping presumable within the brain, but that the per sympathetic response is activated when we put our face into cold water or go underwater. And that's a coming relaxation response.

So this brings us back to I don't want to take us off track from you describe in the study, but this brings us back to the first question, which is, if I go completely underwater for a moment when I start my cold plunge, does that change the physiological outcome as compared? If I just submerge myself up to the neck and and actually, nowadays, that seems to be a little bit of a movement online of people putting a bowl of iced water on their countertop and emerging their face into IT. Do you see this start? I have more and more post about this so um can you just touch on that what the dive reflex is and why IT act perhaps activates the per sympathetic response is coming response well.

so the dividing reflex is activated when you submerged to cool water even .

just to the neck. Yeah, I thought you had to get your face under. I'm not i'm not arguing different. You the expert I just .

wanted yeah I haven't really I haven't read that. I just seen that you can activate your uh that diving response as soon as you should go under water with your body and so you don't have to do with your face as far as I understand that I could be wrong though um yeah so when when you activate your diving response you slow down your m you are oxyde consumption in your body.

That is because the body tries to preserve um oxyde so you will not get hyper thermal too fast. So it's kind of like a survival system in your body. So this survival system is very important for us, of course.

So that will be exhibited. And h because of that, you will after maybe one minute or so, that can be precise on that because I maybe I also vary a bit in in humans. So went to two minutes, you will have full activation of the sympathetic nervous system, but also the parasympathetic va system.

And that's gonna tivat for examples, something like serotonin in your brain, which is like also good for mental baLance, and people feeling in balloons afterwards they after they go up. So that is like missed on a questionnaire and also measured like on on an adults. Of course, people tell the time that they feel good afterwards.

We need studies on there. So if anyone sitting out there thinking that's interesting, then please do some studies on there to get more out of that. Yeah so you had so you observe .

these winter swimmers who are done this for a few seasons yeah they're coming around for a new season of winter swimming and you've decided to recruit a subject they are getting into cold water um climbing down a latter or jumping into the water up to their neck. Yeah climbing, yeah OK climbing down the latter into because this done outdoors. What a fun study to do.

My my graduate thesis was done under flourescent lights with no dows in a building that in a tone of fun as A P H. U. Soon I actually lived in the laboratory as A P H.

Soon I loved IT so much. But um not something require to do A P C, by the way. But um they're climbing down the latter yeah getting in up to their next thing in for one to two minutes and then getting out. And how many times a week are they doing this?

So they do this two or three times per week. And for each time they go, each day they go, they take three rounds h off. So three dipt and two sons as sessions, so they start in the cold, and they end in the .

cold water OK. So get in for one to two minutes, then get out and get into the sooner. Yeah, what is the temperature of the sooner?

About eighty degrees. sales. us.

okay. Then how long are they in the sona?

So they stayed there for ten to fifteen minutes. So depending on if they went two times per week or three times per week.

okay, and then they get back into the LED for a few minutes.

Ah two minutes up .

to two minutes. yeah. Okay, then back into the sona fifteen minutes or so. Yeah then back into the cold for a third round, back into the sona and then then they're ending on and then back into the cold again and then ending on cold yeah and we will talk about why it's important to end on cold the so all sober principal um how cold was the water in this particular given average because I realize its outdoor winter swimming. So it's going to very depending on wind chill and .

things as well as of course so it's a very uncontrolled vironment to do this kind of studied in. But I wanted to do something that was also very close to something people can do for free, going out nature and use stead and also have the nature like it's a very healthy impact on, I think, our stress, a stress level as well. So by doing so, I also measured the temperature every time they went.

So I have this graph and is actually in the winter swiming book IT shows the temperature and and mark going like from october to April and it's like starts at twelve degrees, I think is around twice twelve degrees sells you the water and then he goes down to two degrees in on average in january and then up again. And so it's within the spectrum of very cold border, I was said from around fifteen fifteen degrees so and down. But IT was actually not colder than like two to four degrees, like in in on average when I was the so IT doesn't have to be that code to be good enough and and enough to activate our metabolism.

In what time of day are the participants doing this cold sona alternation?

So I think they did this uh h throughout the day. So I didn't control whether they wanted to go in the morning, in the afternoon or or in the evening. At the time where I set up this study, I I was not controlling IT in that way.

I wanted them to go whenever they had time. And I also think that is the most important message to give out, to give to people is when do IT when you have time? It's not if, if, if doing IT when you get home from work.

And it's six o'clock in the evening and this is the time where you are a where you can do IT then then try out if it's gonna act you sleep or not ah if IT doesn't impact your sleep and fine but you have to try for yourself and find out what works for you. Is the same for coffee, for exam, right? Some people can drink coffee in the evening and go to bed and they can sleep. H, I can't .

or excise .

exercise exactly. So I can, I can do that. And that's because the coffee exercise of water emotion is going to exhibit your sympathetic nervous system.

You have an increasing stress response in your body and and that's onna make IT really hard to fall asleep. For some people at least. Maybe you are super exhausted anyways, and then you will just crash anyway. But yeah but that that's the only thing so I just told him to do this if they can, during the daytime and that's primarily what .

they also did and then along you're measuring ground fat by way of this infrared uh camera right? Um so what did you observe in terms of changes in Brown out? How quick did that occur? And then i'd like to ask also about sona a bit more because earlier you mention that you can activate round fat with sona as well, with heat the surface of the skin.

How long did IT take before you observe significant increases in Brown fat? And was the increased density of my Brown fat or distribution? Was that you know showing expansion to different regions throughout the body? And maybe you could also touch on some of the changes and insulin sensitivity .

in metabolic ah a very good good question and and I didn't mention this before, but besides measuring uh temperature h as an outcome for profit activity, we also did pit M R R scanning h of the Brown feet so this is like the the golden standard uh for measuring Brown feet and is not very feasible for Normal people to get. And and a pit A C T or pit M R I scanning of the Brown fat is super expensive.

So we had both h to see if we could have like a continuous a measure of Brown fat in humans, because that was already not not out there. So I wanted to see during both the experiments, old days, but also during day and night, what kind of like the agent random do we have in our Brown feat activity? So that's why I wanted have that as well.

So the pdc t scanning or the pit M R R scanning was to see upon code activation stimulation for some hours. Do we have exhibition? Can we see the Brown fed in this subject? And also during thermal, true of thermal comfortable state. H how is that exhibited in each of the group, of course.

Ah, so you want to see how comfortable people were away from the cold water and sauna just had different temperatures environments.

Is that right? yeah. So also missed the dead. How comfortable are you? I I made the scale, like visual analog scale, and ask them, how comfortable do you feel with this temperature and and throughout the study days, during cold exposure and themal comfortable day had a whole day where just kept them a thermal comfortable to see.

Do they activate the Brown fed if they are just completely firm, comfortable, as good as we could get with that because you are asking people um on a scale phone one, one to ten and five being very comfortable, where are you on the scales of one would be very cold and ten would be sugar burning hot yeah and so there was a way to like try to figure out how do they actually feel also during the studies. So I also measured a in electric biography. H so of of muscles to see, do they severed during the cooling day? Sometimes people shiver up before they know that really shivering. So I had interesting. yeah.

So it's all a conscious perception of shivering might not be the best read out of shiver yeah.

If you also get adapted to the cold water, you will have less shivering. There will be less vigorous, they will be very small. So you wouldn't probably know that you are shivering because this version is so small and the mystery in the muscle cells will be so dense that IT doesn't need to shiver maybe that much to get that my genesis going. And compared to when you are completely new h to go water exposure, you're not adapt IT. Then the body needs to create these mysql, these energy fabric to keep you you warm and that's or so what the exercise is in the beginning. But um when we measured this, we did see that the winter swimmer were shivering less h or uh having less uh bigorre shivering when they said i'm code so even though they they perception the perception of the code was pretty similar in in the in the groups and we could see that the the activation of the the muscles that we measured on were different and more picture in the control group were the subjects incentivize .

to be in the study where they paid or anything of that sort? They just happened to like doing cold and sona. And so that's why they did the study.

Well, they got paid a little bit for IT, but not .

much and that's how we do this. So so what did you discover in terms of changes in Brown fat, insulin resistance or insulin sensitivity rather, and metabolism?

So what we we saw, uh, was we had this kind of different measures, uh, to see what to try on, well, what what's actually going on when they are already adapted to the cold water compared to a control group who was matched on on various parameters. We we did see that the winter swimmer had an increase insulin sensitivity. They produced less. Uh on all the experimental days.

So besides from just cooling them and measuring the Brown fed on each of these cooling days or two cooling days and one the more comfortable day, right? So I wanted to measure insuing when they just they were fasting, meaning that they hadn't eaten in eight hours before the study day, and and they were completely length, still not moving, just in a bed. And and we measured insulin h during the experiment, just to see how what level are they on.

And we could see that the the winter swim had had lower production of insuing. And they also when they had and glue strike. So we give them that to see if they to test before we enroll them in studies to see if they have diabetes, for example, and not knowing, for example, that that that would like brewing maybe the study.

So we tests for that and see if they have like a Normal curve. So what was this seen? That was that the winter swimmer had faster glucose clearance in the bloodstream. So after two hours h we could see that they had a lower level and went the curve went down faster than and in the control group.

So despite having lower inside and released, they have Better blood. Blue coast clearance, which is really what you want, what we all seek, right? You excessive is bad being a um more less a chapter one for a blood blue coast can do all sorts of other things as well, of course.

But and having hyper lood lue cose obviously terrible for cells, especially brain cells, I don't think people realize how toxic hyborian glue cose is. Having high goods start if you want to kill neurons, you make you make their put in an environment where there's too much sugar oh yeah yeah very neurotoxic. I mean that's and their mechanisms like insulin in that buffer that you know keeping blood lue cose in a reasonable range so that um that doesn't happen.

I think I think that's why people will go into insane mic shock hypoxia. Mic shock is also possible. So that range in which neurons are happy is a not a tremendously hard range.

Incidentally, the ranging in which neurons are are a happy and surviving uh is much greater as one gets colder than when you heat up. I mean, you can basically destroy brain cells by getting too hot for too long. Oh yes, yeah. You can developing stroke brain cells permanently by getting too cold for too long. But if you have to get really, really cold.

very, really long time yeah yeah very .

interesting yeah we were talking about doing an episode on um um survival of the brain after death kind of things which actually happens. You hear about these people who are declared dead and then come back. And there is actually now a lot of cry preservation type approaches for that.

This is where we risk going into the the the esoteric council. Here us back to our discussion about your study. But so if I do the math, these subjects are in the cold that say they're doing three rounds of cold for one to two minutes, three two or three times as a week.

What were the threshold that you discovered were important for getting these positive changes in um such as reduced blood sugar or clearing to blood sugar um being more efficient ah reduced in silin um improved ground fat distribution and density. How much cold exposure do people need? How much heat exposure do people need in order to extract these benefits?

yes. So when we calculated the numbers together, we can see that this was ended up being eleven minutes in total per week h so not in one session, of course, but they had two to three visits to the water. And the sooner powe. So when we divide that out, IT corresponds to being in cold water one to two minutes at a time, but also in the sun at ten to fifteen minutes at a time. And I think this is very like also similar to what we see in other studies.

When we look, for example, to the observation studies from the finish cohort study from log in D L, for example, they published this very amazing paper in two thousand and fifteen um some results from this long core study where they show that um that up to thirty minutes uh in the sona was a healthy and they you you lower your risk of cardio asics and that's like the trust hold. And if you go further than that, then there is not more in healthy benefits to gain from that. So and before that is like nineteen minutes, then you will have this those response relationship up to nineteen minutes. That's really in decreasing your risk of cardiovascular diseases.

And I think with per week ninety minutes, per week ninety .

minutes procession. Now sons, yeah, procession. If we then compare that with my study, which was ten to fifteen minutes percession, then I think IT fits very well with what we call the homework stress or healthy stress, that you expose the cells to this kind of like potton very h stress, the situation a where they h increase heat shock ports in the cells, and that will repair the cells.

But if you then overdo IT and you go beyond there, maybe thirty minutes in the sona, this observation study from finland with more than up to two thousand and bathers, when I fall of these for twenty years, they see that thirty minutes procession is like enough. And if if you go above that, you don't get more health benefits out of IT. So I think there is a window where we can say the healthy stress correspond to like ten minutes and and think .

it's like .

sound procession and it's it's not much actually. So you don't to IT shows that you don't have to expose ourself very much to the heat or very much actually to the cold to get this healthy benefits from going into cold, going to heat, and healthy benefits on your cardiac lar system. So I think this is very important also method to to to get out that you don't have to go extreme.

You don't have to a swim for a half hour in the cold water. You can go in the water for one to two minutes percession, but go up to seven minutes per week in total. And for the sona, my study showed fifty seven minutes in total per week.

And if we also then divided out on these two to three days and two sessions each day correspond to ten to fifteen minutes. So it's a low resole, but I think it's it's good to have that too. Maybe we can aim for that if if people need to have something to to aim for.

And I think and I think it's really good to have that because then you you don't have then you don't overdo IT. And if you overdo IT, you exul to sell some that will increase your risk of cards. See also. So well.

I get a lot of questions about this, and I did solicit for questions for this podcast on on twitter. And one of the questions that I got was, as one becomes more cold, adapted to the benefits, start to wear off, can people do too much cold, the exposure? Of course, the answer to that is, yes, you can become hypothermic.

But i'm sensing a different answer now, which is, if I understand correctly, um the threshold is eleven minutes total per week of deliberate cold exposure divided into two or three sessions of maybe one or three minutes depending on how long somebody stays in and then fifty seven minutes I want to be careful not to around up to an hour but divided into maybe three twenty minute sessions or so you know um so one doesn't have to be perfect as long you get a beyond that real but I I wonder something which is is IT the case that if somebody said, oh, you know, i'm just going to do one eleven minute session per week that might actually not be as beneficial is dividing IT up because what you told us earlier is that the hermetic response depends on having that cold shock. You actually don't want to become too cold adapted. I mean, once the blood pressure response drops down to a minute four, five in six, yes, you're getting very cold in your shivering.

But one is not getting the automatic stimulus that they want. I guess I could like in this to um if exercise worked in a way where IT was only the first few minutes of exercise that really triggered the adaptation. Of course, this is not how works, but in fact probably quite the opposite. But if that we're the case, then it's not simply the total amount of exercise but dividing up the the the sessions into little bouts where every single time IT access IT as a stimulus that seems to be the key here. Um this is very important um because having watched the landscape of this on social media but also in books and generally, I think you're the first person really touch on this that the goal is not to get so cold adapted that you can see in for the full seven minutes in one session where the goal is to be able to do in an hour of very hot sona if you want to do I suppose people could do IT for other reasons. But if the goal is to improve these health matrix, then the idea to keep the stimulus, a stimulus short.

the yeah great.

Well, this also, I think there's practical feasibility, as you pointed out, is getting into a cold shower, cold emersion or natural body water for a couple of minutes is far less um you know chAllenging the most people in finding a full morning to go spend there. Um but i've never really heard IT articulated that the longer sessions might not be beneficial and might actually be detrimental. That's very important.

Were there any other observations that you made on that did not make IT into the paper or that were kind of in the the margin notes and in terms of psychological benefits um or anything of that sort? There was this recent study and soldiers that talked about weight loss sort of a controversial study um for a lot of reasons um but one of the things they remarked uh in the paper was that there were a lot of psychological changes improved buffing against things ID. They even the men and women in that study um reported one of the significant effects was um significantly improved sexual satisfaction.

I've got they can tell us what that meant for these subjects but as so we won't go there. But but a number of subjective improvements. Was there anything that you observed or took note in in your study that graves didn't make the main abstract but that we should be aware of?

Uh yeah there were some um and I am today I regret that I did measure on sleep for example. I I Frankly didn't really think about that when I I when I decide to study and so we were very um uh occupied with the metabolic and I had the thought maybe this could have impact a sleep quality um and I wish just I had the thought that why don't you just ask them in a question now but I ask them every morning or everyone who was not many money just two mornings actually and we measured on but the winter swimming ers um told us before I rode them that they had a really good sleeping ality.

The control would also had that but they told me on the day when we measured Brown fat on on the day, on the night is so if actually two days and two nights and they told me that they didn't they had a good night sleep, but they also woke up. So it's just telling me that they also had like a quick wake up and then they fell asleep again and they went to swimmers, told they have a really good sleep. So it's like in india, or they always say, we we sleep very well.

I sleep very well. So it's anecdotical general corresponds to what I heard in my study, but nothing that I measured on which which could be fun to do in the future. But we didn't measure on sleep quality.

That would have been a really good idea to do. They also told me that they were very comfortable when they were called. They don't mind when to them as they don't mind um going out for example, um in in the cold with A T shirt. They were also less uh scared of showing the skin. There is also .

one observation testing, so kind .

of the social so comfortable in the lab, you as you just meant to before coat on everybody turning around is very busy. And um I was the other um scientist out in the whole way and also my supervise ahead her office down down the hallway and and one of the winter swim as one day just got out of bed after I had been in the study for eight hours, we was a long day, right?

He jumped out of the bed and had his cloth in the bathroom and he went out completely naked. He didn't care. He just went out. He was like.

so that's a side effect perhaps of getting too comfortable with the cold and we're not recommending that. Although in your book you um did you dedicated some let me start again, although in your book you dedicated some pages to um naked winter swimming or I should say naked cold water exposure and as opposed to um uh with bathing suit yeah are there any data on this? I'm sorry, struggling, but um I think in most places in the united states is skinny dipping is is not legal. Most public beaches there are a few, in fact where I I my laboratory before moving a stanford was in santiago and I at the sole institute for biological studies. Beautiful building, incredible science is done there the beach right below that is called black beach OK and um and it's a no nude beach um and so whenever tourists were heading down the stairway there, I would you serve, let them know, especially if they had kids i'd let them know, you know and it's a new beach of a particular of a particular genre so I give them a little a warning about what what they could expect down below it's in any event, those beaches are quite rare in the united states maybe compared to europe I don't know um but yeah maybe yeah so is there anything special about um clothes versus closed exposure?

You have thin in that since h we have a big more free with this kind of life.

But remember, we also had this winter swimming for so up hundreds of years, and then and the winter of the oldest wind ter swimming clubs that we have, especially the one we have in copenhagen, where I did my next study, which we have a talked about, but and it's also not publish yet, but in that winter, swiming club is the oldest one we have in its huge and they they swim naked at this facility, men and women, men and women. And they have shona where they can go in together. And they also have separate zones, but is very much a denis thing.

And and I think it's, I think it's I think it's good if people want that. And I had IT in my book because people want to know if they have to swim with their beating suit on, or if they can take IT off, or what's the what's the difference? Is there any difference in this? And if you ask me, there is no difference if you have your little skinny beki on, is not gonna do any difference to your cold exposure or your adaptation? Is not going to do any difference for benefits, of course.

But I think that he has something else. IT has something to do with how you also absorb yourself, how you absorb your surroundings, and is some sense of freedom in skinny dipping. So I think people in then, Michael justice, is they do the winter swimming because they feel free when they do.

They come home from work, they go to this and they skinny do, and they feel like in touch with nature, and they have maybe done this the whole life. So this is an old to tradition. And denmark in some of the clubs.

And but the new year clubs are coming. They don't, they don't skin there. So everyone has bathing. So I never skinned because that people around, people with phones and taking picture all the time. So different.

different nowadays thing recent .

yeah yeah and also this this old tradition is also fading away because of that .

yeah I um I use on and called at home but when I travel there's a bona so russian bona has hot on and called plunge there's one in seven to school called our committee bona and that one is clothing optional. And so some people are clothes such as myself, and the other people are not. And it's code most of the time.

I think they have male, a female separated evenings or something like that. And then the other bony is spy eighty eight, which is an new york is an amazing bona as well. And these are starting to crop up in different cities or maybe theyve been there for a long time in a deliberate cold exposure and sona, it's more popular, more people are using them.

That the one in new york that I that spider is always closed. Um and it's interesting because people here naked or skinny dipping and they might get certain ideas in mind IT. Yeah all these places are very well let and they all have a tone of kind of um of health is about the kind of health and and and wellness. Um I guess the point being that um there is no requirement uh to do one thing or the other. Um although in the studies that uh you did obviously people were closed but I I did um I did pay attention to those pages in your book that is interesting that you put some some dedicated passages in your book at related to this and .

I think my publisher wanted that was like, yeah he was not me. I was like my publisher really wanted to have a little discussion about that's like.

okay, well, I think you know IT points to a larger, which is I think for a lot of people who already do these practices, um there's no shock there yeah um for people that do not do deliberate cold exposure or sona, I think that um you know there is this idea perhaps that h you know these are um traditions that are are kind of friend sure that they're and I just I want to um cue that point because there are so many things that are happening right now in biomedical research and medicine you serious quality per reviewed studies publishing excEllent journals like you are paper on things like deliberate cold exposure sa um the use of particular supplements natural natural urbs and supplements I mean is an entire branch of the national institutes of health in the united states dedicated just to the study of supplements and behavioral interventions for like meditation and breath work really incredible incredible and psychologically of course being something that for a long time was part of a certain community and feel and now is being a Frankly adopted by mainstream medicine even farma a so the times are changing um and so yes, I think it's important to know that um it's perfectly acceptable and encourage to work clothing.

So ablution absolutely. yes. And one other thing that I wanted to to mention going back to your questions around with there were any observations in the studies, which we really maybe haven't discuss yet and maybe it's in in the back of the the paper and not mentioned that much, was one of the winter swimmer didn't have any Brown fat when we measured him zero zero and uh in we do see this um in in in previous studies as well that some humans don't have any Brown fat was he did he Carry .

a lot of White fat and opposed to show he was he obese?

No he wasn't. No he was not obese because that he would not happen in the study then.

Oh, right. Yes, you mention this early.

Forgive me. No, no, no. But he was. But what I did observe before, a new, that he did have any brand for west, that during the cooling experiment where I cool them for two hours before they go into the pet city scanner, he was not able to control his shivering like the winter swimmer could so he got he got very uh h cold very easily uh, compared to the others so and without, I didn't know what was different about him.

But we could to all all of me and the three others were working on the experiment. We were like, okay, what's going on? Because we turn down the the temperature.

But he started like shivering. And then we had to turn IT up again. And IT was just all over over the place.

The temperature is not IT wasn't that controlled like the others? IT was pretty similar protocol. I could just do pretty much the same because there were same size also save gender.

So IT IT was easier uh to like for see what was gonna en and when will they start driver I quickly learned that. But with this subject there was just with this volunteer was just very much different. And then when we stand him and didn't find any problem for I, I, I didn't even think about IT. So when we scan him, we didn't see anything. I told the pcc people who like, oh, you put up the wrong scanning technology yeah in .

the technology is like this scanning .

look like the thermonuclear day, the thermosetting table day, where we also scan them to see if they have any Brown fat. So you have made a mistake, I was pretty sure. And the reanalyses and analyze this scanning, and they just concluded, well, if the scanning was fine, the experiment went well.

I was just that he didn't have any Brown fat. So he was like what we just in the paper called Brown fat negative. So he didn't have any. And in in my studies be called and knock out, so I didn't have any Brown fair.

So what the observation with him, and I think that would be that's interesting, is that he both shivered very early on and didn't regulate his temperatures as well. He also told me that then he was like a five on the scale of how comfortable he felt with the cold. And out of so IT was from one to ten, and five being three more comfortable and ten being very a cold and and one very hot. So on this slight scale, up open down and he he was like more open down on this scale than any of the others.

He was an observation that I did um but we did see in his blood samples also that his blood samples look a bit more like the control group also his in sum levels were like the control groups are a little bit higher than the other winter swimmer and he also had uh you his block blue coast clearance was not as as fast as as the the other winter swimmer so he was like an outlier what we call IT and indian analysis. We also had to take him out of the analysis because he was an outlier. And so the results showing that the Brown fat uh is more efficiently activated in the winter is without him having him in that group. But I didn't rule in the the study if I tried to put him in in as well, did he didn't room into the results or anything? But just to to keep IT more clear, we put we to come out of .

the analysis. yes. So he was a mutant. okay. Yeah and i'm sure they're out there. Um very interesting. So if you shiver early um then perhaps you have less Brown fat to begin with. Although targets include from one person that sort of the the the implication there or .

you have an adapted to the code so you should build that up yeah right.

So in addition to looking at regulation of blood sugar, Brown fat, meta lisp and so on, were there any markers that you examined in the deliberate cold exposure group as compared to controls um that revealed to that deliberate cold exposure could have additional benefits um say for uh immune system function um or for any function for that matter?

Yeah so for we looked at inflation tion, of course we made the outcome of blood pressure and zone, but we also measured i'll six in the study just to see and inflammatory and in flam mat ory marker. So i'll six went up and IT also follows with the i'll ten. So that is like also very known in the literature. So we measured that. And I think it's very important to to think about the cold explosion, the heat exposure as something that then lower the inflation tion in the body.

And if we can do that, we will have an open door for um preventing lifestyle diseases, right? So for um tech two diabetes, but actually also for some mental diseases as well, so known as depression and anxiety, also alzheimer disease which are all associated um in researchers also newer research showing that h at that inflation tion increases the risk of depression in society and as time must have no logical diseases. So if we can decrease inflation tion in the body, we will decrease uh, modern lives other seasons, but also these increasing a mental diseases that we see in these modern lives at times.

And so I think that I think is very interesting that we can go out in nature and we can use these natural stressors. And I don't want to have IT sound very romantic or anything. It's just it's just exposure to temperature, actually just a cold A R to heat that is going to track our body into a natural state again and and reset IT where the the home stays, the baLance has is lost a bit, so the body is gone to repair itself in that way.

And I think is beautiful, that we can do that just by changing the temperature of our body. And although people are very scared of doing this, because in our times we have been away from cold, away from heat temperature h for some for decades now um since we isolated, our house is Better and we are more secondary. We also sit more indoor.

We don't move as much. So this very modern sedentary lifestyle has made a small temperature comment, just neutral. So no no wonder I mean that obesity is increasing. We don't expose ourselves to the natural stresses that we did earlier on um in in our involvement.

But until maybe the seventies, the sixties where we started having more like comfortable lifestyle, right and obesity increases in the in the eighties, we can see that from statistics. So I think that if we can take in cold and heat, and you mention other things also before, but of course, exercise is very important here. And also a bit of fasting actually, because IT all increases the homework stress in the body, so IT doesn't have to be a other than natural stresses to the body, which then could keep us in the natural baLance. Again.

could we talk about what I referred to as the suburb principle, which is to end on cold? And the reason I called that the sobering principles because um in reviewing oh by the way I wasn't a official reviewer of your paper but I mean in reading and um reviewing your paper for its after published contents, I noticed that you had people end on cold and this has been a long standing debate in the the deliberate cold exposure community should you warm up in a with a warm shower afterwards to get back in the sauna what should you end on colder and on heat and the sober principal says end on cold as I understand IT, in order to force your body to heat itself back up and thereby increased metabolite further still.

Is that right? yes. So when you when you end on the cold, you you force your body to heat up by itself and that would require that you activate, you keep your Brown fat activated and also your muscles, which is a good thing.

It's a good collaboration to keep your thermo genesis up. And that's like an an exercise even when you go home. So in that way, you don't have to think about your cold exposure dipping in in your plunge.

You can see you what IT is as just an exercise that you do for one to two minutes and then is over. If you end on the code, you haven't exercise for your body going on for hours afterwards. And that's not only on your metabolic, but is also gonna.

Keep your new transmitters activated as well and increase that because your body is still cold. So you need that those new transmitted to activate the Brown fat as well. So that's going to make your Brown feet sells more efficient and also your mother sells more efficient, increasing metal congo and the cells, which will then generate heat very fast. So if you have done this for a few times, so maybe three, four, five times, and being new to this, but have tried IT a few times, you will notice a switch where you like, feel that you get easier, warmer and you can keep yourself warmer. And that is also what we shown in in my study, is that the they went to swimmers, were physically a warmer on the scheme compared to the control group.

So they when they are out of the cold.

when they're out of the cold, just relaxing. And we tested this in in on the days where they were sleeping in the lab. So we could see that they had, uh, a more activation of the Brown fat, higher temperature.

So probably because they also lose heat h they have a higher heat loss to the body compared to the control group um because they have a more regular a scheme eh, because of the contrast of cold and heat. So they lose heat faster from the body during the day. But is that a bad thing? No, probably not.

Because that's gonna keep your Brown fat and your most solution activated. So you would have to IT has to work to keep you warm. And I would .

hypothesize that IT also might lead to some of the subjectively reported improvements and sleep because in order to fall of sleep, you need your core body temperature to drop by about one to three degrees, yes. So it's not just sufficient to be sleeping in a cold room and under the blanket, you also need your body temperature to drop. yes.

And so what you are saying, you understand correctly, is that by forcing by ending on cold and forcing oneself to heat up naturally um that increases the Brown fat stores which I see as I like the oil in the candle of the furness that is thermogenesis and that in turn leads to increase heat loss, which people might think so. I don't want to lose heat from the body, but we want to lose heat from the body. Basically something what we want is to be a very efficient heating and cooling system.

Yes, that is not about being cold or being hot. It's really about keeping the system tuned well, keeping the oil in the candle is Brown fat functioning. What could I ask one question about um theater fasted IT is there any rather are there any known benefits of doing deliberate cold exposure endorser fasted versus after a meal say within the last hour something in that sort?

I do my deliberate old exposure first thing in the morning so in general and faster because I don't eat in a little bit later in the day. Yeah but what's known about that and was that looked at in your study? I know you measured glucose, but that was as a separate test away from the cold.

away from the cold. Yeah, but I also tested blue coast on the days on the cold. So we missed that as well.

on. On the cooling days, specifically on fasting and fed. I don't know H I don't think that I have seen studies specifically .

on this um more science needed a number of people ask about the use of deliberate called exposure to offset some of the symptoms of various diseases。 Now here we're not talking about curing disease, were talking about offsetting symptoms. One question i've seen quite often as whether not people with rain ode syndrome, this is a syndrome.

And my high school girl end had this syndrome, and i'll never forget. And we went at a school dance together, and this was when we first start dating, and he had three nodes, which leads to very poor blood flow to the a the extremities and um and he was very cold. So SHE left to go to the bathroom and warm up her hands in the warm water.

I was left standing there at the dance, and people came up to me and asked, you know, why I was there and who I was there with? And I kept telling them who I was with. And they didn't believe me because I can't believe that he would be with me make total sense if you knew me at the time I was.

I was wait out of my league with her at the time. I like to think eventually I caught up. In any case, um SHE was in the bathroom for about an hour so at one point I did consider the possibility that he had just left but indeed he hadn't SHE warned her hands back up.

But people with rain ode suffer from this um from this thing of very, very cold extremities be their fingertips even turn blue um you know as if they were starting to get hospital. It's quite dramatic um and that question gets asked whether not there's any use of cold to trying increase the um elasticity, the plasticity of the of the small capitalists and vessels by everything you've described up until now. Seems like that would be a logical thing to do. Um and in addition to that, whether not people with auto immune conditions, people with um any other time types of conditions are known to benefit from deliberate cold exposure. I'm not aware of any studies, but I get asked about this a lot and there were a lot of questions about this for you in in the twitter .

feed yeah thank you for those Christ and I get them as well on social media. I have to say that I I haven't seen any studies directed a on this outcome. And misery right now is syndrome.

Um I do know that it's it's it's not that rare actually a problem. And I know that many women or more women and men h suffer from this. And but logically, IT would help them if they expose their hands to cold and also heat to make the IT more regular.

But and I have heard from people saying that he had helped them, but also heard for some others saying IT didn't help them. So studies are needed on this specific topic. I think I heard my hands when I go into the coin. I don't have this cinda medal. H, but I keep my hands above the water.

You.

yeah, I do that in often. I take a little bit of a swim, and then, of course, I have to have my hands in the water. But IT helps me when I then get back to the daddy and then take my hands up because then I can stand there for a little bit and get my one to two minutes exposure, uh, and then I can go out because then otherwise that would stop me from being in the water enough time that I, as long as I, I would like to.

So if people suffer from having this pain in the fingers and IT, IT can be very intense. So just take the hands up a bit from the water and the, and that's gna help you. Also, boots, european boots is gone to help on defeat. Some people have the hurt field, the pain in the feed and or in the ankles and that's gonna help them also a little bit.

okay? So there is no problem with keeping hands out or feet in uh, new prem goodies. If people feel the need to do that, if that's what the if pain of the hands or feet is a barrier for people doing deliberate called exposure, then IT seems that would be OK to do to keep hands out or to keep your feet. Yes.

because you do get the exposure of, but of course, hands and feet are very potent places in your body to get a fash exhibition, a of your nervous system, of course. But if you can just you can also just dip them and then take them up. It's going still gonna activate that. But you have your full body is covered in, in the corporation tor, you have a full activation anyways. So you are providing .

very really reassuring information to people because I know a number of people that do not like to book their hands. And I find that the more of my body I get in, the more comfortable I am. I I don't know what psychological and or physiologically.

I find that if where there's an interface between the water and the cold, it's most uncomfortable. So I prefer to get everything under. I keep my head out, although I these days i've been dunning all the way in and then coming out and then dunk once more with my head under before I get out after the the plunge.

That raises a different question. Now we're getting to come the practicalities of deliberate called exposure, which I think are are important. Um sometimes I experience and I hear from a lot of people that they'll get a kind of back of the head headache at the interface of the of the water.

Um you know when they're doing cold emersion to the neck O I assume this has to do with blood flow that there's visual construction right up until the neck and in the region surrounding but that maybe they're still blood flow to the head. But do we know what the origin of these headaches is? And again, this doesn't happen for everybody but some people to experience them.

okay. Yeah I haven't really heard about that one specifically. So but I would say that there are different reasons for maybe keeping your head out of the water. But IT seems like maybe for some that could be a reason for like just getting .

like a quick head. And that's what I started going to eliminate, wasn't getting heads I could. I noticed that interface and I wasn't in the rest of the experiences experience of IT so much. So I started dunk all the way. And I noticed in some of the photos that you've put out and in your book that you'll sometimes where a cap while you go in.

yeah OK and well IT comes from uh, different reasons. Uh, so let's talk about some of the physiological reasons. So when you submit cold water up to the neck study have shown, and this is from denmark, studies from a peaceful ppi, a hospital and that h, when you submerge into cover up to the neck at zero degrees, so zero degrees sales is very cold. And you have a decrease blood flow to the brain by around thirty to forty percent and makes sense because you activate the sympathetic tic via system, uh and and therefore you will have a less blood flow to the brain, makes you maybe a live this year and .

proof again that you you need a heart more than a brain because when the synthetic nerve system gets activated, a blood flow is maintained to the heart to keep you alive, but obviously taken away from the rain that keep you from thinking. That's why it's hard to think .

when you're yeah what the muscles and then then your vital organs need to you have to be able to run away from that tiger.

right? The rational of the total sense who are mind to disagree with .

mother nature well, but yeah so one of the reasons being that you should keep your head out of the water is that you could increase that a decrease in blood flow to the brain further if you dunk the head.

So there is this a very nice paper from from a research group in canada where they have collectively uh h looked at different papers where they h compared heat loss in a group in the papers where they dunk the head and compared to heat loss, uh submerging up to the neck to see how much extra heat do we lose from our car when we dot the head so ah and I think is very interesting that which you submerge up to the neck, you have a heat loss of eleven percent from the body. Cor and when you then uh also drunk the head, you will increase that heat loss rate by thirty six percent. So that means i'm not saying that i'm not i'm not here to say what is right and what is wrong.

I just think that people should know the information so they can for themselves evaluate what is best for them. But if you increase your heat loss rate by thirty six percent from your core, that's gonna increase your after drop, which we touch upon liba earlier even further. So that meaning that you are closer to hypothermia, then you are if you just sub much up to the neck.

So you should really think about whether this is like something that you want to do, or if it's just Better for you not to get that code in your core. The bene is also because I have a little bit of sensitive ears, so meaning that if there's wind and because we swim in the open scene and then mark, we have a lot of wind, our with our conditions are just very rainy, very windy. And when the temperature is also freezing, you could get this um widely cold, so very cold and light headed just from wind.

So if you also stop merchant to coward and you then get up, you you will get a brain phrase immediately. So IT is enough to just go to the neck wherrit y to just not get D C O. So because the um the heat loss is increased, of course but I also the blood flow to the brain has decreased so the meeting will keep you a little bit warmer so you can stay for one to two minutes.

So it's just a way of like getting around some of the conditions also. So people can choose that if they they feel there. But it's quite Normal to do in in scanner abia where a bini of IT.

And so for those of you afraid of doing a two minute cold shower, doctor solar just a described let's uh you see um SHE and others are capable of doing things far harder than that um when did the way you describe IT with the cold wind and skin avia is quite striking along the lines of covering the head. There's this seemingly paradoxically thing of people going into hot songs and wearing wall caps.

You if you go to urban ia or you go to song, and there are people who are. Um well from eastern europe are typically or finland or um russia, a ukrainian elsewhere. What you'll is that many of them are wearing well caps in the sona, which many people think is to make IT hoder. That's actually not the case that actually insulates you from the heat environment. The the sense of urgency to get out of the hot sona is a brain driven mechanism.

And so um the reason that people wear well hats in the sona that actually lets you stay in the sona longer, because IT takes a lot of heat to the skin before you feel that you you d have to get out where as so when you insulate the brain um you don't get that signal。 It's pretty interesting. I have tried this before just by putting a tail over my head in the sona, you can stay in there.

You're much more easily and for much longer you as we talk about these different stimuli for the homemaking response, the adaptation distress IT occurs to me that the big ones in our evolutionary history have been light, right? I mean, you were talking about seasonal changes. Um we know there are specially as you go up to the countries, there are seasonal changes in the amount of light by time of year, dramatic ones, in fact.

So at the equator, of course, light temperature, food movement and it's sort of interesting and and at the same time, perhaps that should have been obvious to us that there are stimulating. Our bodies have evolve to adapt to in very powerful ways. And so the idea that temperature, heat and cold could evoke these tremendous physiological changes that are beneficial for us, I surprised us at all.

I mean, I mean, this is why, I mean, these are not so terc mechanisms. They are actually that the foundational mechanisms by which our body and the bodies of other animals adapt. So I do have a question about the different ways that people could approach deliberate called exposure. So for instance.

ince um children .

i've been the bonist where their kids in six or seven years old with their parents at the Bonnie and so they're in hot sana. I'm not suggesting people do this if there if they are not you know adapted to IT and you talk your parents kids and talk your kids parents after your daughters, but is remarkable.

I mean, children doing sona from a Young age or deliberate cold exposure, are there any date on this? And is IT safe, assuming that you know obviously that they can swim in or they're doing this in in a tuber shower? Um and then i'd also like to ask you about are there any additional male female differences? I know your study focused um on men, but um other studies have focused on both and of course um are women and connected to your own experience with this. Um so children, men, women, um differences there are in terms of protocols is anything that people should build into the structure of their deliberate called exposure that's unique to that.

Uh so yes, so this was on cold exposure. So um yeah I think that um starting with the the question about children um I think that is important to to think about as children are smaller than adults so we cannot really completely transferred all the information and the benefits and also protocols for how long and and stop like the two children. We cannot do that because they are your smaller and mass.

And one study that actually improves this is a study where they have compared a heat loss in a children, boys who were twelve years compared to adults, men, and looked at heat loss of the cold temperature and expose them to a, at one or one or two minutes, cold exposes or emotion up to the neck. And what I saw was that the, the, the boys in this study could actually defend the cold temperature in the same way as the adults could, but they had to use the muscles way fast. So IT means that they couldn't stay for as long, uh, and they use more energy to defend their cold temperature compared to the, to the adult spot for one minute.

IT seems that they could actually come, but they would be colder when they then come, because they are smaller in the mass to that. Rachel, right? So that means that if the surface is so large on children and the mass and muscles being smaller to that, Rachel, IT means that they can be an the water, uh, less time before they get hypothetical.

So just think about that. They're just smaller. They can defend the temperature for a very long time. But in this study they saw that for up to, I think it's IT was a minute or so they glad you .

mention hypothetical smaller bodied people, children. I used to do some pacific uh ocean swims in the morning um without wet suits and I adapted to IT pretty quickly. And these are fairly long swimmer and we brought an excEllent swimmer with us um that was in turning with me for a while um is sixteen years old at the time and very lean and he wasn't small for his age, but he was smaller than us.

Then there was all guys on the swim that day. Sometimes women join us and he got hyper atherton c and he's an excEllent swimmer and he didn't report feeling orel cold. But fortunate we got him to shore and he added him up again um so he lived I don't think his mother is gonna ver.

Let him go swiming with us again. He's driving in the world. He's a university student now and he recalls that swim I mean this way you always want to ocean swim with a buddy with people.

Yeah, he he became hy thermic. His teeth turned yellow. He was got slurring his words. He wasn't making sense, and we got him on the shore, and he was, know, dwelling in a little semi euphoria.

Then was hypothesis me is no joke so I think yeah so I am really glad that this is coming up because the cold is a powerful stimulus and um and I and kids are at a and smaller body, people are a greater risk of hypothermia so a good reason to approach IT with caution, maybe start with cold showers, get a then called emersion and still water, natural water and open bodies of water, of course always going to be um more dangerous for other reasons, currents and things that so okay, yes, so important note there. What about any additional male female differences or similarities that um we should be aware of and this comes up all the time on social media. Any time I post anything about a study that is what about women because often times .

there are differences yeah yeah and there we we also just talked about the difference in in, in, in temperature in men and women. So that means that if we did, if we replicated my study in women, IT could be that they would have enough, you can say, cold exposure with just nine minutes per week. IT could be because they, uh, apparently h are also just colder, and and they have, uh, increased metabolism.

The Brown fat is just to have more Brown fat. IT could be, but this is just something that I I rankly don't know. But women also do a cold exposure. Winter swiming. With the eleven minutes protocol, I do IT at my cell and feel good about IT so I would say that women also regarding activation of the Brown fit IT should be the same um in theory but I don't know if women actually do need to have another protocol when he comes to this rapid cold exposure. I think that is another question.

If we are talking about ice swimming, when he comes to how far can you be in the cold water without getting hypothermia? That will be difference in in men and in in female. And but if you do this called exposure for a very brief amount of time, which is what I try to to talk to about talk about the what we call all some microstrip the body to increase the homework stress, the healthy stress, then this is such a short amount of um exposure that is is fairly the same. I think I think women can look at this as a fairly a good protocol for for for them as well.

Always say that if you really read the cold and um and don't like the cold, then you are a perfect candidate for using deliberate cold exposure because the sympathetic okay, the stressed response will be greater and thereby the adaptation to that shorter one or two minutes um is going to be much greater right?

For a bill that are previously comfortable in the cold, it's harder to get adaptation response the same way that have somebody y's very strong and they can lift a very heavy weight that that very heavy weight is unlikely to evoke the same of our same degree of of adaptive responses of somebody is not quite as strong. So another reason to keep these exposures relatively short and and more frequent then to do longer duration exposure frequently. However, let's say somebody only had two days a week to do deliberate cold exposure.

Maybe they don't have access to asana, maybe they do. Would you suggest that they get in for one or two minutes, then get out, then get back in for another couple of minutes, then get out and call that for, you know, four, five minutes to try and get to that eleven minutes total per week, as opposed to getting for a four, five minutes and and then getting out in coming back a second time that week? I know this is getting down into the weeds, but these are the sorts of things that I think people really want to know because a lot of people either don't live close to a body of water or don't have a cold plunge um that they can do this with. Although cold shower apparently works too, so most people live close to a shower.

Yeah it's definitely I think the the changes in temperature is what is a strengthening your cells in the body. So if you can do the short amount of uh, exposure and then get out and get back in, that is kind of, you can say, strengthened yourselves because you are telling him them to to adapt to changing temperatures. So doing one session, you can change this right?

You can do IT if you are able to go to cold water, but also a song than you just do IT that automatically if you will have a change in temperature. But you could also do IT by varying the temperature and your cold plunge, if you have, if you have a plan, show, if you have the open sea, you have seasoning seasons, even you have, we have then, mark. So we have four seasons, and the temperature is gonna vary with that.

So we have nature who can just change this for us. And we don't have to think about IT. If you have a cold plunge, well, then I would say that changing the temperature is what is gonna.

Create this homework stress and also keep your cells on its toes. You can say, because you are tried, the body will still. Be stressed to try to adapt to the new temperature as is seen as something actually toxic to the body. Right is a small, small piece of toxic dating that you are exposing yourself too. You don't have to swallow away, but it's enough that you touch IT actually.

Yeah great. A great way to frame IT. That brings me back to this idea of circadian in your study. You didn't control for specific time of day. And now i'm realizing that may be a great asset to the whole thing. So we know, for instance, that our bodies go through pretty dramatic shifts in temperature from the time we wake up. My body starts heating up as we wake up and continues to heat until the afternoon and then starts to drop in the later afternoon and then assuming all things are working correctly, um that body chemistry drops when we sleep.

So I could imagine that doing deliberate cold exposure at different times um just by way of convenience or by way of intention could be a very beneficial because my body temperature is going to be quite a bit warmer at one time of day versus another and in that way, keeping the system tuned. And that's really what I keep hearing coming through in as you explain these data, all these beautiful studies, yours and others, is that it's not really about getting cold. It's about going from warm to cold and from cold to warm.

It's not IT. And I love this idea because I Price said this one hundred times on my podcast in a million times in my life, and i'll continue to, which is that biology is not an event. It's a like these these metal olic and thermoregulatory processes are indeed like the turning of a nab. It's a verb. Yeah it's as supposed to I now and I and so I I think if people can internalize that idea that they're going to um have a lot more flexibility, a lot more fun in and get a lot more benefit as a business of thinking, okay, I need to get into x degrees of water for x amount of time on x number of days. I get this .

question all the time. How much and how call them? And I mean, it's it's just like, well, because we also don't have studies showing exactly if you just keep five degrees in your water and you do that for a month, then what happens? We maybe the future, we will know much more about this.

And i'm i'm sure it's gonna come and I really hope so. But I just think by logically changing that temperature up and down, up and down and you also do that in your water IT doesn't really it's not that important. What temperature you you will have your water then then just keep changing and going up and down IT could be all up to twelve degrees cells.

You're gonna celery, your grand fat. Anyway, I mean, twelve, ninety degrees cold air is enough to activate your rappers. So maybe we don't have to go as cold as I think many people think. And putting ice even all the time, you don't have to it's I don't think it's necessary to to expose your yourself to that cold uh, temperature all the time and but very little a bit.

So keep the system off baLance and is way to be IT tuned. You mentioned a study that is more recent or an ongoing that's not published. Um if you're willing um could you share maybe some of the data from that findings from that study um with of course the the cute to everybody that these are not yet publish data so the conclusions could change, the data could change for that matter.

Yeah, so we we haven't analysed all the data yet. And I I know from the study that we did publish that we we would need to look more of the data. So I don't really have any results yet that I can share because we are still in very preliminary analysis of this. So I I wouldn't know yet what to exactly say about that, but what we look at was both men and women. So that's that's me.

Oh, that's fantastic. That answer is going to please a great number of people and and and intrigue everybody. So well, I want to really thank you for coming here today to talk about your work um and the incredible direction that IT points to because I think that um you know no one study is definitive but your study really understands as a landmark in the a landscape of expLoring deliberate cold exposure and heat how IT can impact and potentially impact our health because Frankly, there are just haven't been that many um high resolution um the modern studies of this, there have been studies of sona, there have been some studies of cold.

There are a lot of groups and physiology work on um hypothesis mia and very cold exposure, but most of the temperatures using those days just aren't practical. So first all I just want to thank you for doing the work that you've done and for the work that you continue to do. Um uh waiting with baited breath as they say to uh to hear the results of this uh study that's on going on, both men and women.

So have to have you back to about that soon and I want to thank you for the incredible public education efforts that you've been doing on social media um and with respect your book um and we of course we will put links to all of those things in the shown of caption so people can learn from you and continue to learn from you. We we certainly need more scientists who are both experience with doing hard core research, as it's called, and who also do the practices. I think that's a wonderful additional asset. You just behind a lab code or bundled up in in a down, in a down feather jacket as everyone else is getting in the code, you do these things and that you are so open and generous in the way that you share knowledge, which includes coming here today to to share knowledge with me and our audience. So thank you ever so much.

You very welcome. I am so pleas to be here and thank you so much for inviting me and I could explain my study and I can share some of my insights from from doing that. So i'm very grave football being here delighted .

and we will have to have you back again. Thank you for joining me for today's discussion. All about deliberate cold and deliberate heat exposure science and protocols with doctor Susana soberly.

If you like to learn more about doctor sebert research, or you would like to learn about the research of her institute, the sobering institute, please see the links in the shown o caption. Also in the shown caption, you can find a link to doctor soberly excEllent book winter swimming. If you're learning from and or enjoying this podcast, please subscribe our youtube channel.

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