Recap: How to do intermittent fasting properly | Gin Stephens and Professor Tim Spector
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Hello, and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health.

Today, we discuss intermittent fasting with Professor Tim Spector and Gin Stevens, the New York Times bestselling author of Fast, Feast, Repeat. As many of you long-term listeners will know, Zoe ran the world's largest ever study on intermittent fasting. We know a lot of you are interested in the potential benefits, and I'm talking about improved blood sugar control, heart health, and mood. But practically, how do we get started with fasting? You'll find out in this clip.

What am I allowed during this fasting period? Well, let's talk about plain water. Yes, nothing added to it. No flavors. You know, plain sparkling water is also fine. But, you know, people sometimes say, well, how come I can have black coffee and plain tea? Because those have flavors. Well, they do have flavors, but they have a bitter flavor profile. And a bitter flavor profile is not associated with a cephalic phase insulin response.

So black coffee is actually stimulating autophagy. Autophagy is our body's powerful cellular housekeeping. It's like recycling and upcycling where our bodies during the fast can go in and clear up old junky proteins and really clean up things. Also, it's great for our immune systems. They can really function best during the fasted state.

And black coffee is likely to stimulate those processes. It even helps with fat burning. And so black coffee is a great thing to add into your fast. Now, if you

find that black coffee makes you hungrier. If you don't want to have the coffee, you're not required to have the coffee. You can just stick to water if you want. But black coffee does tend to stimulate the things we want to have going on during the fast. And Tim, any thoughts on that? I remember we had a lot of debate when we were doing our big Zoe Predicts studies about whether or not you can have teas and coffees during fasted periods. Yeah, I mean,

I mean, no one knows absolutely for sure because the tests haven't been done. So we're just getting an expert consensus on this, really. But most people do believe in the fasting world that, yes,

Black teas, green teas, coffees, water are perfectly fine. Where people start to disagree is, can I have just a drop of, you know, a macchiato in my coffee, just that tiniest little drop? And some people say, you know, if it's less than equivalent of 10 or 20 calories, it's probably okay. Your body probably won't be able to sense that as a meal and therefore break its fast. Other people, I think like gin, would probably say no.

avoid that, that could be counterproductive and you actually lose all your benefits. I don't think we quite know yet. It may be that Jin's actually tried it herself and seen any difference. Oh, yeah. Well, I have a whole section in Fast Feast Repeat where I talk about the clean fast. And there is at the end of that, there are two chapters about the clean fast. And there's a section where I have anecdotal

stories from intermittent fasters. And, you know, I've been in the intermittent fasting community since well before I ever wrote any books at all or had podcasts really in 2014, 2015 started with the support groups on Facebook. And anecdotally,

The difference between Fast and Clean and putting a little bit of this, a little bit of that, the bulletproof coffee, a little bit of butter, all the things that people might be putting in there, the difference is night and day. And you have to really experience it for yourself. So anybody who's putting in a little sweetener or a little drop of cream or whatever, and you're like, it's fine. It works for me. I'm still losing weight. I feel okay. I would challenge you to try it with the Clean Fast. Give yourself 30 days. I call it the Clean Fast Challenge.

Go to plain black coffee, plain tea, plain water, nothing flavored, nothing sweetened, nothing to lighten up your coffee. I've never had anybody try it for 30 days and then go back to the other way. So, you know, it really, you just take that challenge and try it for yourself and see. Most people report that they can't believe the difference that it makes. So, Gin, just to play back to like somebody listening, trying to do this. So I need to go to a clean fast when I'm fasting. I need to only have like this water and tea and coffee. Right.

Do I immediately go to like some constrained period on day one and stick with it? Help me to understand what else I do in this 28 days.

That's a great question. And, you know, you've really got to build up to it. I like to compare it to couch to 5K. You know, if someone wants to go run a 5K, you don't get off the couch on day one and run a 5K. You have to build up to it. And so fasting is the same way. We're very much building up our fasting, quote, muscle, right? It's not technically a muscle, but you know what I mean with that analogy. So you're building up to it. And that's what the 28 days is really for.

you know, you're learning how to fast clean, there are going to be days where you feel hangry and you have to open your window earlier than you expected. And that's not a fail. That's just part of the process. We're learning to listen to our bodies. You know, we never want to feel shaky, like you're having a blood sugar crash. If you're ever shaky or nauseous, go ahead and eat. You know, forget about what the plan said to do that day. Go ahead and eat.

And, you know, gradually as your body gets adapted, you'll find, you know, what feels good to you. Some people always feel better with a midday eating window. For example, they like to skip breakfast.

eat lunch, have a little maybe early kind of dinner, close their window, no couch snacking on chocolate for them because their window is closed, but they sleep better when they have that middle of the day eating window. I'm not one of those people. I actually sleep better when my window is closer to bedtime. I've tried it all different ways. I wait till afternoon, open my window, eat till I'm satisfied, close my window. But only through experimentation have I learned that. You're not going to learn that in the first 28 days.

I interviewed a longevity expert, Dr. Gil Blander. He said he believes that one of the most powerful things we can do to increase longevity is intermittent fasting. Just have that piece in there. Understand why we're doing it. I don't want anybody to start intermittent fasting only because you might lose some weight.

That's not what intermittent fasting really is all about. Of course, I came to it for the weight loss. I like to say we come for the weight loss, but we stick around for the health benefits. Amazing. And Tim, can you tell

Tell us a bit about that value of that window length, because you could say, hey, just lots of people are eating for 18 hours a day today because of the way that the world works. And what really matters is just to shrink that to 12, which is still like 9 a.m. to 9 p.m., right? That's pretty different from shrinking it to much shorter periods. I think that I've heard you, Tim, talk a bit about some of those, perhaps the microbiome having at least part of the answer to that story. Yeah.

Yes. I mean, microbes themselves have their own circadian rhythms as well, and they're driven just like humans are by food. So when food arrives, that sort of sets them off on their particular clocks and things. And we do know that your microbiome changes as you're fasting compared to when you're eating. So within the 24 hours,

Remember, these species can change and replicate within an hour. They've had new babies and new lives, et cetera. And so what happens when you're fasting is some microbes that

don't live off food, but they live off the debris and the lining of the gut mucosa, suddenly come to life. So when suddenly all that snacking's ended and Jonathan's finished his chocolate, thank God, we can move on, you know, and get all those other chocolate-eating microbes out of the way. And the cleaning staff come out and there's some microbes that

like Accomansia that's well known because it has a name. It says Accomansia municifilia means I love mucus. So it loves the sugary lining of your gut. So it's going around tidying up your gut lining that you haven't rested properly. And if you don't give it a rest, you don't have enough time for these

cleaning microbes really to come out of the woodwork and tidy up your gut and help it regenerate. What's interesting is that these same microbes that have this job

are also seen to be crucial in preventing diabetes and obesity. So, Accomansia is one of these microbes that is stimulated when you go on a fast and is now a very trendy novel probiotic for helping your metabolic health and help you lose weight. So, I think it's, you know, we're just starting to understand which microbes fit into these categories, but realizing that you're getting a whole new team come out

If you give them enough time to come out of the woodwork, tidy up your gut, do all the repair work, and really you're in much better shape for the next time that chocolate bar comes down. It's a brilliant analogy. So it's sort of like you've put the trash out overnight and early in the morning. It's the overnight cleaners in an office that come in and make everything shiny again. It's the...

offense team in American football versus the defense team. You know, it's giving them time to come out so that you've got the right team ready there to deal with your body and what it needs to do. And if you put it out of sync by eating the way we weren't intended to, by eating over 18 hours, it just simply doesn't have enough time to do its job. And I think what we're doing in this fasting is really extending the repair side of the body. And that's probably the general idea about why fasting is so good and why it has

this huge potential in longevity. And so outside of the microbiome, do we have the data that supports that today, Tim? Or where are we on that? Certainly there's really good data in all these animal models where it's easy to study these sort of things. And there's biomarkers in humans that suggest the same thing. So I think there are these multiple mechanisms going on that are complicated, that are

all pointing the same way that this is really essential for the body's repair process in the cells and in the gut. And so, Jen, is the consistency of the timing important? So, in other words, I'm going to start eating at midday and I'm going to finish at nine and I do that every day. Is that very important to this being sustainable and easy or can I just do it sometimes?

The consistency means that you're doing something every day, right? It's consistency of the fact that you maintain a fasting protocol. That doesn't mean it has to be the exact same timing every day. It's just a matter of like, we don't like, quote, take days off. We don't have cheat days. I mean, that doesn't mean, though, that you can't decide today I'm going out to brunch and I'm going to eat at 10 o'clock.

And, you know, what worked for me really well was the idea of, you know, keeping my eating window to, you know, like five hours and shifting that around. So if I wanted to shift it to earlier in the day, I could do that, just slide it to a different part of the day. And then, you know, one day my fast was a little shorter because I opened my window earlier, but then I closed it earlier. So the next day my fast...

you know, was a little longer because I opened at the time I normally did. So we don't want it to feel regimented and lots and lots of rules that you must follow. You're saying it's not fixed. It's not like I have to do it the same time every day. You're actually relatively flexible, but the duration of the window, I'm sort of keeping constant, even if I change it from day to day.

There are plenty of people I know that just, you know, will do this for two or three days a week and they still feel better generally when they do it, but they're not so rigidly fixed. That's it for this week's recap. If you're listening to this, you're already on your way to living healthier through better nutrition. And at Zoe, we're doing everything we can to help you on your way. So we've developed Daily 30, a delicious dietary supplement to add to your meals.

Because we're Zoe, we ran a clinical trial testing Daily 30. The results were staggering. It's selling out in the UK and we're working hard to bring it to the US as soon as possible. Sign up to the waitlist at zoe.com slash daily30.