Jim Hill: Welcome to Weight Loss And, where we delve into the world of weight loss. I'm Jim Hill.

Holly Wyatt: And I'm Holly Wyatt. We're both dedicated to helping you lose weight, keep it off, and living your best life while you're doing it.

Jim Hill: Indeed, we now realize successful weight loss combines the science and art of medicine, knowing what to do and why you will do it.

Holly Wyatt: Yes, the “And” allows us to talk about all the other stuff that makes your journey so much bigger, better, and exciting.

Jim Hill: Ready for the “And” factor?

Holly Wyatt: Let's dive in.

Jim Hill: Here we go.

Jim Hill: Welcome to this edition of Weight Loss And… Holly, I'm excited about today's episode for two reasons. One, the topic is one that everybody is interested in - intermittent fasting. And the second reason I'm excited is we have our first guest. One of the things we have is access to really smart people. Before I introduce our guest, one of the grants from the National Institute of Health that we have here at UAB is called the Nutrition Obesity Research Center or the NORC. We get funding to support nutrition research of all our investigators and we have over a hundred researchers here at UAB that are part of the NORC. There are 11 of these nationwide, and they help grow and develop nutrition research. And Dr. Peterson, who is our guest today, is a member of our NORC. She's also our colleague here in the Department of Nutrition Sciences at UAB.

Courtney is an associate professor here. She is absolutely one of the top people in this field. She has a lot of funding from the National Institutes of Health. She is at the cutting edge. Courtney combines chronobiology, nutrition, and metabolism.

I'm excited to hear how all that is going to come together. She's doing a huge trial right now on intermittent fasting. And Courtney is one of the smartest people I know. And it's a real pleasure, Courtney, to have you on our podcast today.

Courtney Peterson: Thank you so much. It's great to be here.

Holly Wyatt: That's what I was going to say. She's one of the smartest people I know. And I am so excited that we get to have her as our first guest. I mean, this is like one of those people that nationally people are asking to come on and talk.

Jim Hill: So she's in the news all the time talking about her research.

Holly Wyatt: We rub elbows with her. We can get her, right?

Jim Hill: We know her. We can get her autograph for you.

Holly Wyatt: We know her. So, Courtney, we want to just pick your brain. We want to know what you know about this subject. We're currently witnessing numerous articles in the popular press discussing intermittent fasting, also known as timed eating or time-restricted feeding.

There are lots of different terms. Maybe you can even help us with that. So we just want you on here to kind of clarify what that is and what you know and kind of tell us all the cutting edge. And we always end with practical tips because that's what people want. So we are just open and really glad to have you here. So share with us.

Jim Hill: When people talk about intermittent fasting, to me, that's a catch-all. And there are several components to that. Maybe start there, and then we'll get into your research.

Courtney Peterson: Great. So intermittent fasting is a term that encompasses many types of meal timing strategies. And the common theme behind all these strategies is that you're alternating periods of eating and extended fasting. Intermittent fasting used to be defined as fasting on water only or no-calorie beverages for at least 24 hours.

But recently we've seen a big shift in the definition. And now most people define it as fasting for at least about 14 hours a day or longer. You'll still see some people defining it as fasting for at least 12 hours a day or longer. But I'm part of an international consensus committee of experts, 35 intermittent fasting experts around the world, and we've agreed on a 14-hour longer definition.

Holly Wyatt: Yeah, I love that.

Jim Hill: That's great to get that many scientists to agree on anything, Courtney. That's awesome.

Courtney Peterson: Well, we all agree this was just the final voted option.

Holly Wyatt: Well, in the State of Slim, we adopted that. I went and talked to Courtney, and she said, I was like, “Okay, I'm out there. There's all these different hours. And I don't.” And she says, “Okay, this is what we think. We may learn something different, but this is what we think.” So we went with 14 hours. So I like it. We're we're there with you on that.

Courtney Peterson: That's great. So under this umbrella, there are a ton of different eating strategies that are technically intermittent fasting. Most people think of only a couple of different intermittent fasting strategies. So I'd love to define the landscape. So intermittent fasting largely arose from different religious traditions around the world. So you can think of Ramadan fasting, actually the most common form of intermittent fasting in the world.

And that's where you dry fast during the daytime. Dry fasting means not only do you do classic fasting where you eat no calories, but you drink no liquids, too. And either do this for a month during the month of Ramadan. So a lot of these fasting traditions came from different religious traditions. Another example would be fasting one day a week for 24 hours or 36 hours, depending on how you define that. More recently, we've seen other intermittent fasting approaches, where, for instance, every other day, you'll have a complete fast - that's known as alternate-day fasting, or every other day, you might eat one meal a day - that would be called alternate-day modified fasting. It involves not completing a full 24-hour fast, yet consuming a highly restricted calorie diet on those particular days. Another example would be the fasting-mimicking diet. So this is an approach where you're trying to recapitulate a lot of the benefits of extended water-only fasting. Typically, in this approach, you will eat around 800 calories for three to five consecutive days. They found that this approach provides many of the benefits of intermittent fasting.

You see an increase in stem cell production after about three to five days. And you see a lot of these benefits of intermittent fasting. And more recently, the most popular form of intermittent fasting by far is daily intermittent fasting. And that's when you fast for at least 14 hours a day every day. So that means you're effectively extending your nightly fast between dinner one day and breakfast the next day. And you can do that either by eating breakfast later in the day and or dinner earlier in the day.

So there are a bunch of different ways to do that. So that is now the most popular way to do intermittent fasting. And I'll add one more intermittent fasting strategy that's become quite popular, especially in Europe, and that's the 5:2 diet. This was very popularized after a BBC reporter did a documentary on fasting. So for the BBC and in this type of approach, you pick two days a week to eat a very low-calorie diet. So typically the equivalent of about one meal a day.

Jim Hill: So Courtney, what do we think are the benefits of these sorts of different meal patterning?

Courtney Peterson: The basis of intermittent fasting comes from the idea that our hunter-gatherer ancestors didn't always have food available. And so they had these periods of extended fasting. So if you think about the fasting state, if you eat a meal, the first time when you're first digesting that meal, you're burning mostly those carbs, fat, and protein that are in that meal. As time elapses that you've been fasting, then your body will start to burn through most of that fuel and start burning through glycogen that you have stored in your body.

So this is a form of stored sugar that you have in your body. And as you kind of deplete these glycogen reserves, then your body starts transitioning to burning more fat. So it's burning fat for fuel. And what we know is when your body starts to burn fat for fuel, it turns on a sort of reparative and rejuvenative process in the body. So for instance, we really start to see after about 11 to 13 hours of fasting, we really start to see a big increase in something called autophagy. And autophagy is just a fancy word for recycling a lot of damaged and worn-out proteins in the body. We can clearly observe that our bodies possess an incredible ability to repair much of the damage inflicted upon them on a daily basis. And the punchline is we know some of this molecular damage can raise our blood sugar levels, can cause inflammation in the body, and so we think by having these extended fasting periods that the body turns on a lot of this sort of like self recycling and self rejuvenated processes and makes us healthier in the long term.

We also know with the extended fat-burning period that insulin, which is a blood sugar hormone in the body, those levels go low or insulin levels go low. And so a lot of other positive sort of programs are turned on in the body. So for instance, we know when insulin levels are low, that inhibits the growth of cancer cells. So it gives your body the signal to kill a lot of these sorts of pre-cancerous cells in the body. It does that by lowering a certain molecule called IGF-1, which is a big cancer-related molecule. With longer fasting periods, your body eliminates excess sodium consumed in your diet, which reduces blood pressure. Furthermore, there is additional compelling evidence. For example, in the brain, the production of a hormone called BDNF serves to protect and regenerate many neurons. Imagine an incredible orchestra of various bodily processes working together to repair and maintain your health during longer fasting periods.

Holly Wyatt: That makes sense. Given our current environment where food is constantly available, it's important to consider the practice of intermittent fasting. Without consciously integrating fasting into our routine, we may never experience a break from constant eating, as food is always within reach. What if our bodies were designed to have a specific period during which insulin levels decrease, enabling repair and rejuvenation as you mentioned? It does seem quite logical when you think about it. So I love how you explained it.

Jim Hill: It's really exciting, Courtney. But one of the questions I know a lot of our listeners are asking is what about weight? If you're trying to lose weight, is this a good way to think about losing weight?

Courtney Peterson: Yeah, great question. So this area becomes a little bit more controversial, but I'll happily share some encouraging answers as well. Extended fasting periods, such as around 48 hours, can put the body into an optimal fat-burning state. This could result in greater fat loss with intermittent fasting. And it could be that there's something intrinsic that you're just burning more fat, for instance, in preserving more muscle mass. But there could be other factors involved.

And this is where the debate comes in. So if you have this rule not to eat at certain times of the day, that prevents people from snacking. And a lot of people do snack, or there are a lot of temptations to snack or eat either mindlessly or not mindlessly. So you can imagine someone sitting in front of the TV at night just grabbing a snack and kind of reflectively doing that.

Intermittent fasting may work by making us more mindful positively. It's a really simple rule. And I'll tell you, because we do also some research on diet quality in my lab, it's far easier to give someone a rule like “don’t eat this time” rather than teach them “broccoli is healthy, refined food is not.”

So it's an appealing rule that a lot of people like. Over 50 studies have been conducted on daily intermittent fasting and its impact on weight loss. And then we call this daily intermittent fasting time-restricted eating.

A little bit of an unfortunate name, but we're stuck with it. So time-restricted eating or TRE. But in this daily intermittent fasting, we have over 50 studies now. And the exciting thing is that about over three-quarters of those studies do find that people lose weight through intermittent fasting. And we, recently, my lab recently did a systematic review and it's quite interesting. Research consistently shows that restricting daily food consumption to eight hours or less can lead to significant weight loss. Whether someone chooses to eat just one meal within a four-hour window, multiple meals within six hours, or spread their eating within eight hours, numerous studies have consistently demonstrated positive outcomes in terms of shedding pounds compared to initial weights. So we would say relative to baseline. So there wasn't necessarily a control group, or even if there was a control group, as long as the control group was given keep maintaining your normal habits, etc. And so I think that's exciting and encouraging. But once you get to 10 hours a day…

Holly Wyatt: How much weight loss? That's what we want to know.

Courtney Peterson: The amount of weight loss is typically about two to three percent over about eight to 10 weeks. And we did a study recently, and we found very similar results. And what we did, we took that data and we used some mathematical models and we kind of said, “OK, what sort of calorie cut is this weight loss equivalent to?” (most important to note) And when we modeled the data it was equivalent to about a 214-calorie-per-day deficit. So this is about modest to moderate.

Jim Hill: That's very cool. You get a little bit of an effect, but it's something that for a lot of people, it's fairly easy to do.

Holly Wyatt: Or something you might, can add on to something you're already doing. You're making some better choices. And now you're going to restrict the time that you eat. And that's going to help with weight loss. And then potentially all the other stuff you said, right?

Courtney Peterson: Yes.

Jim Hill: And Courtney, we talk a lot about weight loss, but we also talk about weight loss maintenance. Could this be a good strategy for people who have lost weight? We did, for example, a show the other day about the new weight loss medications that are good at producing weight loss, but the challenge becomes keeping it off. So could these strategies be used for weight loss maintenance?

Courtney Peterson: Yes, we think they will be very helpful because one, you have this kind of nice rule to follow, which kind of keeps you on track. And we know a lot of weight gain, for instance, happens around the holidays. And I'm not saying you have to follow intermittent testing perfectly around the holidays, but, maybe you go off the diet for a couple of days. And then go back on and, kind of blunts that or reduces that weight gain every year. The other fascinating thing is we've done studies in my lab where we put continuous glucose monitors on people. So these are blood sugar monitors that tell us what your blood sugar level is at different times of the day. And what we found is intermittent fasting really kind of reduces these spikes in blood sugar that people get. When people experience sudden spikes and drops in their blood sugar, it can activate the body's hunger response. And there are a bunch of molecular reasons why that's the case, which I'll skip over. But we find those spikes are lessened with intermittent fasting, even when we feed people the exact same food. And so we may be naturally reducing that hunger in folks as well as giving them just general strategies.

Jim Hill: So that leads to a question I've been wanting to ask you. How does chronobiology fit into all of this?

Courtney Peterson: One of the biggest debates out there is whether the time of day that you practice intermittent fasting matters. Most people who practice intermittent fasting do so by skipping breakfast and then eating later in the day. And you've probably heard over the years, oh, you should eat breakfast.

That's good for your health. And the data seems so controversial. It's so hard to make good sense of it. I would like to take a moment to discuss the fascinating topic of the internal biological clock, also known as the circadian system. So inside our body, we have this biological clock, we call it the circadian system, and it's better at doing certain things at different times of the day. So for instance, when it's dark outside, and I'm going to say something that sounds obvious, that's the best time of day to sleep. That's where you get the most regeneration from sleep, you burn the most calories when you sleep actually at night. So some people don't know this, they burn more calories when they sleep at night than during the daytime. So there are all kinds of reasons why your body's optimized to do different things at different times of the day. So for instance, your best sports performance is in the afternoon. Now in most people, though there are some exceptions, their best blood sugar control is actually in the morning.

It's mid to late morning. It's truly intriguing because we've been aware of this for nearly 50 years, yet at first, we were unsure how to make use of this discovery. During the development of our initial blood sugar tests for diagnosing type two diabetes, the focus was on comprehending the functionality of these tests. And they noticed if we give this test in the morning, people's blood sugar doesn't spike as high. And back then we didn't know about the existence of the circadian system. And if you fast-forward a few decades, we learned, okay, so we have this circadian system, and this system is making our blood sugar control better early in the day. And so this does suggest that people should eat early in the day. Numerous studies have demonstrated that following the traditional advice of eating a hearty breakfast, a moderate lunch, and a light dinner leads to greater weight loss, improved blood sugar control, and other benefits. So there is very clear evidence now that eating earlier in the day is better for health. And I can't do it fully justice here, but that gives you a flavor of the research we have. But with intermittent fasting, where you skip breakfast, okay, maybe you're missing some of the benefits of eating breakfast or eating early in the day. However, you may still be getting some benefits from intermittent fasting. How do those two doctors play out against each other?

Jim Hill: It's complex.

Courtney Peterson: So it's complex, I think is the answer.

Jim Hill: What excites you about your science right now?

Courtney Peterson: So I'll finish that along these lines. Currently, we are conducting a study to determine if skipping breakfast can yield most of the benefits associated with intermittent fasting. So we have a big cool study now where we have, we're taking people and they get assigned to one of three groups. So one group's a control group, they eat their meals over 12 hours. The second group does daily intermittent fasting or this time restricted eating by eating a seven-hour period early in the day. And then the third group eats in the same seven-hour period, but they do it by eating late in the day. So they skip breakfast. So to me, this is the million-dollar question.

Jim Hill: Wow. That's a great one. I'm very excited about those results.

Holly Wyatt: Well, I love it because it just shows that we think we know something, and we have data to support it. And then there's something that kind of comes in and goes, well, wait a minute, we need to question that. And then we study it again. And then it just evolves in that it's always this “weight loss and…” because there's so much more to it. And it's never-ending, right?

It just continues. Scientists should never claim absolute certainty, as nothing in science is ever truly absolute. We must always embrace the idea of continuous exploration and discovery.

Courtney Peterson: Yes. Based on my analysis, it is highly likely that the group that practices early-day intermittent fasting will reap the greatest advantages in this specific study. But if we find that skipping breakfast and doing intermittent fasting is better than eating three square meals a day spread throughout the day, I think that would be such a huge positive finding. So many people would be willing to do that.

Jim Hill: But Courtney, do you think not one size may fit all? Some people may be better with one strategy and others with other strategies.

Courtney Peterson: Yes. And we saw this in one of the first studies we did. We did a study where we had people do intermittent fasting early in the day. And this was a small study. And seven out of eight people did better eating early in the day.

But one person got worse and very clearly worse. And it was interesting because we found out later, that he did night shifts. And we made his blood sugar worse. And so he needs a different time of day to eat. One of the big questions in the field too is in people who have type two diabetes, their circadian rhythms are different. Their biological rhythms are different. So do they need to eat at a different time of day or do we need to improve their underlying rhythm? And that's something else that we're studying in my lab, too. We're measuring their circadian rhythms before and after they eat early in the day and trying to see if we are making their health better, or worse. Does it depend on the person? Does it depend on their underlying circadian rhythms? So we're also measuring their circadian rhythms.

Jim Hill: In an upcoming episode, we will explore the fascinating topic of precision nutrition. Join us as we delve into the intriguing realm of understanding individual differences and uncovering the remarkable insights they hold for optimizing our health. But we're just at the beginning of doing that. This is such an exciting research area, Courtney.

Holly Wyatt: I have some practical questions. Some listeners might be thinking, "Okay, I love it. I'm bought in. I like it. I want to try it. What do I do?” So first off, it sounds like 14 hours is kind of where you're sitting right now in terms of the time to do the fasting. Is that right?

Courtney Peterson: Yes. I think people will get better results if they fast for at least 16 hours. But what I recommend as a starting point for most people is to try to fast for 14 to 16 hours and then take it from there. I think that's a great starting target for most people.

Holly Wyatt: Okay. So that's good. What about, can you eat anything? Like people always ask me, like, what if it's like a splash of reduced fat milk in my black coffee? Can you eat anything? Or is there any leeway? Or what do you think about that?

Courtney Peterson: Not really, to be honest. It probably breaks the fast, but it probably depends on what exactly you're doing. Like, right, if you squeeze a little bit of lemon, that's going to be less than five calories in water. No problem. Have fun. But if you start to eat something like an energy bar that has 100 calories or more, you're probably breaking your fast.

Jim Hill: And it's a slippery slope. You start with a little bit and you do a little bit. So maybe the best answer is to be pretty rigid, no calories.

Courtney Peterson: Yes. And I'll say the other thing that we found in our studies is there's a clear adaptation period, which means if you suddenly jump on the bandwagon, we found that participants sometimes find it harder until their body adapts. And many people start to see that their body starts to adapt after about two to three weeks.

Holly Wyatt: Two to three weeks. That's good to know.

Courtney Peterson: And it makes sense because they've been these great studies on Ramadan fasting, and they find after about a month, people's some of their hormones that regulate appetite, start shifting and adjusting to the new time of day that they're eating. So we're thinking at this point that you have to kind of retrain your body to do it at a different time of day and then it becomes easier.

Jim Hill: Give it a while before you evaluate whether it's good for you.

Holly Wyatt: That's important. I didn't know that. And I think that is a huge message to get out there because I think people are willing to if they know things may get better after three weeks, they're willing to try it. And I've had some of my patients on it saying it's really, really, really hard, and I don't feel any different or whatever, but maybe they didn't try long enough. So I like, that's a perfect tip. What are the most significant mistakes you have observed, either from your own experience or by observing others?

Courtney Peterson: That is a hard question. So I guess a couple of things that come to mind is I generally recommend that people have a break day each week and we do that in most of our studies. And the reason why I think people tend to take an all-or-nothing approach. And so in nearly all, we have one exception lab, but in nearly every study in the lab, we tell people to stick with it six days a week.

Jim Hill: That's new information.

Holly Wyatt: That fits because we do like an indulgence meal. So it's almost like you can indulge in one indulgence meal, but you can have like a day when you and that doesn't seem to affect the results. It seems like you can get right back on and things are good.

Courtney Peterson: Yeah. And I think the biggest thing is sustainability, right? If you tell someone they can never eat out, who's going to stick with that program in the long term, right? But if you give them one day a week, like the pressure's off, and they're like, I can do this, right?

Holly Wyatt: I love it. It's practical.

Jim Hill: You've got to have a diet that works and one that people can stick with. If you can't stick with it, it doesn't matter. This is great information, Courtney.

Holly Wyatt: So another question, Courtney, do you do intermittent fasting? What do you do?

Courtney Peterson: Yes. So I've been doing intermittent fasting for about 10 years before it became popular.

Jim Hill: Wow. You were ahead of the curve.

Courtney Peterson: I know. I began practicing intermittent fasting before even researching it. However, around 2008, I came across a captivating podcast discussing a study conducted by Mark Matts. The study involved participants consuming their meals within a four-hour window and fasting for the remainder of the day. And at the time, I was like, wow, well, that's very different. And I was intrigued, and I tried it out and just thought, this is fantastic. And I'd also been thinking in parallel about how powerful fasting is. But fasting for an extended period, like a week, is extremely difficult. And there can be safety issues too. And so I kept thinking, like, how do you get the most out of fasting but in a sustainable way that someone would be willing to do for a lifetime, right? Because fasting for 24 hours, one day a week, is a big burden.

Jim Hill: You want that eating pattern that you can do forever.

Courtney Peterson: Correct.

Holly Wyatt: Well, I just think you brought up a perfect point. If someone's listening, and they're too diabetic on insulin, they need to talk to their doctor before they jump in and do this. I want to emphasize the importance of adjusting medication, particularly those that regulate blood glucose, to ensure people are aware of this necessity. It doesn't mean you can't do it, but you've got to talk to your doctor first.

Courtney Peterson: Correct. So we are studying the daily intermittent fasting in my lab, that time-restricted eating. We haven't seen a major increase in side effects, but in most other forms of intermittent fasting, you have to be careful about medication adjustments, especially if you're on any glucose-lowering medication. Please talk to your doctor about reducing your medication by half or 70% depending on your condition.

Holly Wyatt: Yeah, you can do it. You just need to talk to your doctor first. All right, Jim, do you do intermittent fasting? Have you practiced this at all?

Jim Hill: I do because of Courtney when she told us the 14-hour thing. I've been doing it now for a few months and I do it. When I start eating, I'm about ready to go eat right now. I skipped breakfast today after eating around 10 o'clock. This made me quite intrigued by your study, as I am curious about the potential positive effects breakfast may have.

So that's going to be a great study. So yes, I've been doing the time-restricted feeding. I haven't been taking a day off and this is, you've made my day, Courtney. I'm going to start doing that. What about you, Holly?

Holly Wyatt: I do it, but I have to admit I'm kind of episodic about it. I probably don't sound like I'm as consistent. What I've found personally, it works well when I start to feel cravings or start getting starving or I notice for whatever reason, and this is just anecdotal. This isn't a study. This is the Dr. Holly study of one person, but when I feel like I'm starting to crave food a lot and I'm having to push back against cravings or think about food a lot, we call it mind chatter or I'm thinking about food, food, food, food, food, food, sometimes tend to make sure I go into that intermittent fasting can kind of decrease that or stop that. And I wonder if it's not breaking some of the patterns of insulin or some of just some of the things that you've been talking about. So I tend to use it a little episodically, but hey, 2024, I may change my mind. I may start to use this.

Courtney Peterson: And let me say one other thing. I think if someone listens to this podcast, and can only do it five days a week, that's fantastic. In a lot of our studies, we find the vast majority of people can do it five, five and a half, or six days a week, like about 80% of people doing that. So I don't want anyone to say, oh, I can't do it six days a week, beat themselves up, and fail. I would say if you can do it five days a week, awesome.

Jim Hill: Wow, Courtney, this is wonderful information. And I think you've given our listeners some ideas of maybe trying some things. And the research here is just fantastic. And we're going to have you back on when your study results come out and as we learn more. Thank you so much for being the first guest on Weight Loss And...

Holly Wyatt: It was great. Thank you. Bye, everybody.

Jim Hill: And that's a wrap for today's episode of Weight Loss And ... We hope you enjoy diving into the world of weight loss with us.

Holly Wyatt: If you want to stay connected and continue exploring the “Ands” of weight loss, be sure to follow our podcast on your favorite platform.

Jim Hill: We'd also love to hear from you. Share your thoughts, questions, or topic suggestions by reaching out at [weightlossand.com](http://weightlossand.com/). Your feedback helps us tailor future episodes to your needs.

Holly Wyatt: And remember, the journey doesn't end here. Keep applying the knowledge and strategies you've learned and embrace the power of the “And” in your own weight loss journey.