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Home » Podcast » Reset Your Body’s Metabolism for FASTER Weight Loss & LESS Hunger In An Era Of Ultraprocessed Foods, With Dr. Jason Fung.

Reset Your Body’s Metabolism for FASTER Weight Loss & LESS Hunger In An Era Of Ultraprocessed Foods, With Dr. Jason Fung.

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Reading time: 5 minutes

What I Discuss with Dr. Jason Fung:

  • How calories are an oversimplified measure of obesity, emphasizing that different foods impact metabolism and fat storage differently, and challenging traditional views like “calories in, calories out”…05:18
  • The energy balance equation, and that calorie intake and calorie expenditure are interconnected—reducing calorie intake alone doesn't guarantee weight loss due to the body's ability to adjust its metabolic rate…11:49
  • Microbiome, digestion, and hormones, like insulin, affect nutrient absorption, fat storage, and overall health, with emphasis on issues like SIBO and hormonal imbalance…17:55
  • Efficiency of marathoners, their physical and mental optimization, including lower heart rates, focus, and reduced energy waste, as well as debunking the myth that exercise alone burns significant calories…25:49
  • Individual differences and habits, like consuming high-calorie foods post-exercise, further complicate maintaining weight balance…29:07
  • Hunger is primarily controlled by hormones rather than the timing of eating, with examples like exercise suppressing appetite and medications like Ozempic influencing satiety through hormonal pathways and brain regions like the hypothalamus…35:36
  • How body weight is regulated by a “body fat thermostat,” controlled by hormones like leptin, rather than purely by calorie intake and expenditure…43:44
  • The benefits of dense, bulky, and harder-to-chew foods, like vegetables, which provide volume and encourage fullness while being nutrient-sparse…49:28
  • How blending food pre-digests it, making it easier to absorb but leading to faster glucose and insulin spikes, which can alter hormonal responses…52:33
  • Negative effects of ultra-processed foods on hunger and weight loss, highlighting how they stimulate different types of hunger and contribute to unhealthy eating habits…59:58

On this episode of Boundless Life, I geek out with Dr. Jason Fung, unraveling why calorie counting alone doesn’t explain weight struggles. Dr. Fung uses jaw-dropping stats, like nearly identical calorie consumption between nations with wildly different obesity rates, to illustrate how hormones, digestion, and even the microbiome play a much bigger role than just numbers. From insulin-spiking cookies to satiating salmon, this show will have you rethinking what you've been told about fat loss and hunger.

We also break down the three types of hunger—homeostatic, hedonic, and conditioned—and explore how ultra-processed foods hijack your biology. Dr. Fung shares that ditching processed foods is his top strategy for conquering hunger, while I reveal how staying busy and using GLP-1s can help curb appetite during fasting or travel.

Dr. Jason Fung is a physician (kidney specialist), researcher, and New York Times best-selling author currently practicing in Toronto, Canada. His books, including The Obesity Code, The Complete Guide to Fasting, The Diabetes Code, and The Cancer Code, challenge conventional thinking about these diseases and introduce dietary strategies to manage them. The Obesity Code has sold over 2 million copies and has been translated into 33 languages in 36 territories across the world. Dr. Fung is also the co-founder of The Fasting Method, a program that helps patients lose weight and reverse their type 2 diabetes naturally.

In Dr. Fung's new book, The Hunger Code: Resetting Your Body’s Fat Thermostat in the Age of Ultra-Processed Food, he continues this exploration to understand why humans are susceptible to problematic eating. Dr. Fung also introduces the concept of the body’s “fat thermostat”—a biological “set point” that regulates how much fat your body tries to maintain. Guided by hormones and metabolism, this internal system drives hunger and energy use, explaining why lasting weight loss requires more than just willpower.

With three Golden Rules and 50 actionable tips, The Hunger Code empowers you to recognize and respond to hunger appropriately. You'll explore how to slow digestion, break emotional eating cycles, and overcome social pressures to eat constantly, so you can maintain a healthy weight (from scratch, after fasting, or after using weight-loss drugs).

 

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Do you have questions, thoughts, or feedback for Dr. Jason Fung or me? Leave your comments below, and one of us will reply!

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Ben Greenfield [00:00:00]: My name is Ben Greenfield.

Ben Greenfield [00:00:02]: And on this episode of the Boundless Life Podcast. Do you want to know how to stop hunger in its tracks, control how many calories you're eating, and understand how to really reset your body's thermostat for better hunger management, better weight loss? Then keep listening. I'm interviewing Dr. Jason Fung, author of "The Hunger Code." And all the shownotes are at BenGreenfieldLife.com/HungerCode. This one is great if you just.

Ben Greenfield [00:00:28]: Can'T seem to stop eating.

Ben Greenfield [00:00:30]: Alright, here we go.

Ben Greenfield [00:00:31]: Welcome to The Boundless Life with me, your host, Ben Greenfield.

Ben Greenfield [00:00:36]: I'm a personal trainer, exercise physiologist, and.

Ben Greenfield [00:00:38]: Nutritionist, and I'm passionate about helping you.

Ben Greenfield [00:00:41]: Discover unparalleled levels of health, fitness, longevity, and beyond. Well, in preparation for today's guest, I have— I've been fasting for 38 hours. I injected a few GLP-1s. I threw out all my ultra-processed food and, you know, just doing everything, all the things. I'm kidding. My guest is Dr. Jason Fung. Jason has been on the show before.

Ben Greenfield [00:01:12]: He's the author of the international bestseller, "The Obesity Code." I don't think I even interviewed you about that book, Jason. I know I interviewed you about "The Complete Guide to Fasting." which I still consider to be the complete guide to fasting. But now you've written this book, hold it up for those of you who are watching the video version, "The Hunger Code." "The Hunger Code." People get hungry. People sometimes wonder if they should be hungry. Some people don't want to get hungry. Some people like to get hungry. You explain it all in this book. So, welcome back to the show, Jason.

Jason Fung [00:01:49]: Thanks. It's great to talk to you, Ben.

Ben Greenfield [00:01:52]: Yeah, yeah. And, by the way, for those of you listening in, everything that Jason and I talk about is going to be at BenGreenfieldLife.com/HungerCode. And, you know, I think a really good jumping-off point here, Jason, is this idea that calories are the single biggest reason that we gain weight. Or lose weight. And then I'm reading your book and I get to page 8 and there's like this table of countries and the number of calories eaten per day versus obesity. Tell me about this table.

Jason Fung [00:02:32]: Yeah, so, you know, what we're all taught, what we all think is that everything depends sort of 98% on the number of calories, right? Rather than the types of calories or whatever. It's really what's taught to everybody. So if you look in the past sort of 20 years, it's what the doctors were taught, it's what the dietitians were taught, it's what all the scientific conferences say, all this sort of thing. But it's actually not true at all. So you can, you know, simply look at the number of calories that a country eats, for example. So that takes away all their sort of individual will and all this sort of stuff and say, who eats the most calories in the world, right? And it's, you know, it's actually not the United States, it's Bahrain, for example. And there's a huge— discrepancy. Yeah.

Jason Fung [00:03:20]: And the US is second.

Ben Greenfield [00:03:21]: I've never been there. They must have pretty good food though.

Jason Fung [00:03:25]: But the, you know, there's a huge discrepancy in obesity rates, you know, so people will eat similar numbers of calories. So if you look at Ireland, for example, they're actually right behind the United States. So the United States on average will eat 3,868 calories per day. And in Ireland, it's 3,851. So really a minuscule, minuscule difference. But the obesity rate is 30.8% versus 42.9% in the United States.

Ben Greenfield [00:03:55]: Let's see, 3851, 3860, a 17-calorie difference and about a 12% difference in the obesity rate. That's crazy.

Jason Fung [00:04:04]: It's crazy because you go from 30% to 42%, you're talking about an increase in like 30%, you know, 33%, 35% increase in the rate of obesity. Based on this minuscule difference in calories? Like, I don't think so. 17 calories, like, you know how little that really is? Or you can compare two countries like Austria and Germany, for example. So again, very, very close in the number of calories, very close in terms of the people, right? They're neighbors, right? And it's like 3,739 versus 3,648. So again, probably about 80 calorie difference, but a difference of 17% versus 24.2%, right? So 7%, huge difference, right? 17%, you're talking about an increase of about 40% to get to that rate. So the whole point is that it's not simply the number of calories, there's actually a lot more to it. And you can do something like a correlation coefficient, which basically takes two variables. So calories you eat per day and obesity rate, and you can take them and make, do a simple correlation coefficient.

Jason Fung [00:05:07]: And I did that for all 162 countries that were listed in this.

Ben Greenfield [00:05:12]: Correlation coefficient, meaning, meaning, meaning the strength of the relationship between two variables, right?

Jason Fung [00:05:18]: Exactly, exactly. And it was 0.6, which is considered sort of weak. So, you know, if you're looking for a strong correlation, if calories were sort of the be-all, the number of calories, if it's the number of calories is the be-all and end-all, you should expect a correlation coefficient of like 90, 92%, right? And it's simply not there. There's so much other stuff that's going on other than the number of calories, which is discrepant from the way we think about obesity, which is all this— it's all calories in, calories out, a calorie's a calorie, right? There's no identification that, hey, certain calories are more fattening than other calories, right? So that whole idea is sort of way off. And the whole thing about calories is that it's not even a physiologic concept, right? If you take any standard textbook of physiology, right, and look for calories, it's simply not there, right? There's metabolism of carbohydrates, there's metabolism of protein, there's ATP, there's Krebs cycles, all of this stuff, right? All this stuff we've developed, you know, for research over the last 100 years, and calories is simply not in any diagram you can find. Why? Because the way you metabolize a calorie of glucose is completely different than the way you metabolize a calorie of protein or a calorie of fat, right? It's completely different, right? And all it means, like, seriously, all it means is that some foods are more fattening than other foods. It's like, well, who thought that is, you know, such a revolutionary thought? Like, cookies are more fattening than salmon. Like, I take that to the bank.

Ben Greenfield [00:06:59]: Or put another way, you are saying— I don't know, let's stick with the cookie-salmon analogy. That if I eat 3,500 calories of pure cookies per day, that I would potentially have a different weight gain response than the same number of calories of, I don't know, smoked salmon.

Jason Fung [00:07:19]: Well, exactly. And the reason is that the number of calories will be the same. But when you eat those foods, the minute you put it in your mouth, your body responds with different hormones. Right? And it's the hormones that tell your body what you're supposed to do with those calories, right? So, when you eat cookies, you're gonna spike the insulin way up. That's known. That's not even controversial. When you eat the smoked salmon, it doesn't. And again, that's known.

Jason Fung [00:07:47]: It's not controversial. When you eat the salmon, you're gonna push up your peptide YY due to the protein, the cholecystokinin due to the fat. You're gonna push up the GLP-1 because those are the incretins, which respond very well to the protein, for example. So it's like, okay, so you have this huge difference. You know, on the one side you have lots of insulin, no GLP-1, no peptide YY, no cholecystokinin, right? So that's your hormonal profile when you eat the cookies. And the hormonal profile when you eat the salmon is the virtual opposite of that, right? And that makes a difference. Why would you think it doesn't make a difference? Why would you think that the body is, you know, reacting differently and it makes no difference? Like, it doesn't make any sense.

Ben Greenfield [00:08:31]: Well, I will see your insulin example and raise you one. Let's go the other direction. Let's say you have a genetic histamine sensitivity to smoked and preserved food, and you experience a significant cortisol response and rise in stress and potentially inflammation and insulin insensitivity. In response to the smoked salmon, that may also be just as fattening as the cookies for you. So there's a lot to this, right?

Jason Fung [00:09:04]: There is a lot to this. And everybody thinks that you go from foods which have calories, so you go from calories to weight gain, right? And it's simply not true, right? There's this whole— and in The Hunger Code, I describe the whole pathway, which is the food. It goes from food which contains calories and macronutrients, but it must be digested, then it must be absorbed. So digestion is how the stomach sort of prepares it, right? So it goes into the stomach, it's held there, gets churned around, it gets mixed with stomach acid. There are certain hormones, certain enzymes I should say, like amylase, which start the breakdown process. But for example, different foods are going to exit the stomach at different rates, and that makes a difference, right? So that's digestion. Then it has to be absorbed. So it has to go from the intestines into the bloodstream.

Jason Fung [00:09:54]: So when you take glucose, for example, so carbohydrates are glucose. Well, depending on how you process those carbohydrates, so you can take two examples. So you could take, for example, instant oats, which are ground very, very fine, and steel-cut oats, which are, you know, big pieces basically. And the digestion is going to be different and the absorption is going to be different because, because those oats are ground up very, very fine, the way it goes from the intestines, the small intestines, up into the bloodstream is very fast., as opposed to the steel-cut oats, which goes up very slow. And that makes a huge difference. That goes to the next part, how quickly that glucose rises then impacts your hormones, right? Which then impact your weight. So it goes from foods to digestion to absorption to hormones to weight. Like if there's this whole complicated process and we just ignore the whole thing, it's crazy.

Ben Greenfield [00:10:51]: Okay. So I'm sure you've possibly heard this, but I've heard people saying it myself. The first law of thermodynamics says that energy can be neither created nor destroyed. So how does that jive with this idea that it's not just about the calories?

Jason Fung [00:11:09]: Yeah, it's not about the number of calories because this comes back to the energy balance equation. So thermodynamics has actually nothing to do with it because anybody— it's always interesting because You know, the way— and I'll explain in a second, but I think it's quite funny because a lot of people in nutrition talk about thermodynamics and nobody on thermodynamics talks about calories, right? Because it's like the worst example ever of thermodynamics because it doesn't break the law of thermodynamics. So I studied biochemistry, so I actually took a whole course on thermodynamics and it never talked about calories.

Ben Greenfield [00:11:44]: Me too, but I've probably forgotten a lot more of it than you have.

Jason Fung [00:11:49]: So if you look at the energy balance equation, right, this comes as Body fat equals calories in, calories out, minus calories out. So body fat is a store of calories, right? So we can all agree on that, right? And it's no different than, say, your bank. So if you have a bank, then it's the money in minus money out, right? So that's always true. But what it doesn't mean is that if you simply reduce the number of calories you eat, or calories in, that you will lose weight, right? Because remember, there's 3 variables. They talk about this caloric deficit, but a caloric deficit never exists. Remember, it's an energy balance equation, right? So therefore, there are 3 variables that must balance. There's the body fat, which is calories you store— calories in, calories out. So if you reduce the calories in, you could either balance that equation by reducing body fat, which is the energy stored, or you could balance it by reducing the energy you burn, right? So if you eat 500 fewer calories, you could balance this equation by burning 500 less calories, right? And that's metabolic rate, right?

Ben Greenfield [00:12:56]: And then, and not, not to throw too large of an asterisk on your example here, but you've also got storage calories in the form of liver glycogen and muscle glycogen as well. So there's another, what, 2,500 or so that you have the option of burning?

Jason Fung [00:13:11]: Yeah, exactly. So it's actually, exactly. So muscle glycogen is actually segregated a little bit, so it's actually not, not available. Available for regular use, but liver glycogen.

Ben Greenfield [00:13:20]: Yeah.

Jason Fung [00:13:20]: And that sort of sugar. But yeah, you know, to some, it's a bit simplified. So to, yes, absolutely right. But the point is that if, if, if you simply say you're, if you eat fewer calories, you must lose weight. It's not true because every single study of weight loss shows that your metabolic rate goes down. And this is not exercise, right? Because that's, that's different, right? So that's voluntary. You measure basal metabolic rate, which is the energy you need for your heart and your lung and your liver and so on. So the whole, the whole point is that, well, what, how do you balance that equation? So if you simply rewrite this equation and it's simple algebra, right? So calories in minus calories out equals body fat.

Jason Fung [00:14:05]: You rearrange it and solve for calories in, for example, that rearranges to calories in equals body fat plus calories out. Okay, so that's logical.

Ben Greenfield [00:14:14]: Calories in equals body fat, your storage calories, plus calories out, meaning how many calories you've, you've burnt.

Jason Fung [00:14:22]: You've burned. Yeah. So that's just rearranging the terms, right? But what that says is that for every calorie that you eat, your body could either store it or it could burn it. But what that says is that for every calorie that you eat, Your body could either store it or it could burn it. But which one does it do? Because that's really important, right? If you store all those calories, then you're going to get fat. But if you burn all those calories, you're not going to get fat, right? So it's not the number of calories, it's what your body does with those calories. And that all depends on your hormones, because really, honestly, everything in the body runs on hormones. That's how you know, we send messages, hormonal messages, chemical messages, to tell your body what you're supposed to do.

Jason Fung [00:15:18]: So the point is that it's not just the number of calories, because the number of calories doesn't have any impact on what your body does with it. So let's go back to the cookies versus salmon example, right? So you take cookies, you know, 500 calories of cookies, and your insulin spikes way up. Okay, so what happens? Well, insulin is a normal hormone.. And its job, one of its jobs, is to tell your body to store this, those calories because you're going to need it for later. This is the whole point, right? And when calories go— when insulin goes down, you're going to release those calories. So you eat the cookies, insulin spikes way up. So you're telling your body, please store all of these calories into body fat. It could be glycogen as well, right? But for simplicity, we'll say body fat or storage of calories.

Jason Fung [00:16:06]: So, if all 500 calories now goes into storage, well, none of it is left over for you to burn. So, you're gonna just be hungry later on because there's no energy for your kidneys, for your heart, for your brain. Compare that to salmon. You eat the salmon, insulin doesn't spike way up, your body doesn't get the signal to store it. Now you got 500 calories floating around your body, and your body's like, "Okay, well, I'll use it then." there's no reason for it to reduce the number of calories it burns. Right. And that's the point that you have to be a little bit more sophisticated. Calories in, calories out is a very, very simplistic way to look at it.

Jason Fung [00:16:42]: Right. It's, it's sort of this really shallow first order thinking.

Ben Greenfield [00:16:47]: Yeah. I feel like I'm the annoying student in class who keeps raising my hand and saying, yeah, but when you bring up the cookies, I think it was— correct me if I'm wrong— I believe it was called the Day 2 study or something like that, where Even that, the blood sugar and insulin response was partially dependent, I believe, on the bacterial profile of the gut, meaning that your microbiome composition could even affect how likely it is that a cookie would spike blood glucose and insulin versus not.

Jason Fung [00:17:18]: Yeah, actually, there's actually a lot of things that it depends on. This gets back to the the absorption, digestion, how it gets to digested, how it gets absorbed. So the microbiome actually plays a role in that. It's actually interesting because, you know, and the whole microbiome story is sort of new-ish. There's less data in it, but it can definitely affect it. One of the ways, for example, is fiber. If you eat fiber, it goes— it gets— it's not digested, but it gets to the colon where it gets fermented by the bacteria into short-chain fatty acids, which stimulate GLP-1. Which is great because you're, if you're eating fiber.

Jason Fung [00:17:55]: So of course, if your microbiome is way off, then that's going to play a role. And same thing if you have like small intestinal bacterial overgrowth, for example, SIBO, that's going to interfere or that's going to impact how you're going to absorb these things because as it goes in, so you've got to, as you follow the food, the food goes into the stomach, stomach churns it up, pushes small boluses out into the small intestine, small intestine absorbs it. But then as it goes through the colon and stuff, that's where you can affect it. So the absorption the digestion, which affects the hormones, right? And then the hormone— from the hormones, your body decides, hey, how much do you actually store, right? And that's why it's important. You know, when, when you look at it sort of very simplistically, you can say, well, obviously it's important because if you give hormones, you're going to gain weight, right? So if you take insulin and just give somebody insulin, they will gain weight. Like, I could make you fat if I give you enough insulin. You're going to get fat, right? Because I'm telling your body to store more fat. Fat.

Jason Fung [00:18:57]: That's it. And if you don't eat anymore, what will happen is that your body will simply reduce your metabolic rate until you gain the fat that you were told. I mean, I've seen people with, you know, they were burning like 800 calories a day because of all this yo-yo dieting. Isn't the big, you know, the whole low-fat era where everybody was sort of super low-fat and their instance were sky high? Because their instance were sky high, the body kept storing fat and they still kept not eating. So their metabolic rate kept going down and down and down and down, like 800 calories a day, and they're still gaining weight. And people said, no way that's true. It's like, by the time you measured it, it absolutely was true because that's what the body can do.

Ben Greenfield [00:19:38]: Yeah, this is where we're getting into all those subtle nuances of weight loss strategies. I know that one that actually seems to be successful for some people with long-term calorie deprivation are periods of refeeds. To kind of like reset that thermostat rather than long-term calorie deprivation. What do you think of that strategy?

Jason Fung [00:20:02]: I think those sort of short-term refeeds are actually probably successful. I mean, a lot of times you get into this sort of plateauing thing, and that's where sort of breaking it up a little bit can be very successful. I mean, the sort of principles are still true, like avoiding a lot of sugar, avoiding ultra-processed grains and stuff. Those are still probably true. But when you're really low in calories, you may need more of the proteins and the fats and so on. So, I mean, I feel like protein's sort of getting a day in the sun sort of thing these days. Everything's protein this and protein that, but, you know, probably reasonably deserved, you know, and fat sort of has sort of made its way back up.

Ben Greenfield [00:20:43]: Just try to eat 3 chicken breasts for lunch and you'll understand. And I guess the big takeaway message for me so far is put Put kale and chia seeds into your chocolate chip cookies. There we go, podcast over. Okay, so I have a very active audience, relatively active audience related to weight loss and what we've been talking about so far. You discuss what you call the exercise myth, and you say that you reject the exercise myth. Tell me about that.

Jason Fung [00:21:11]: You know, exercise is interesting because it's actually obviously very, very good for you in a lot of ways, right? Um, so if you look at longevity, if you look at health, if you look at almost any measure, exercise improves it, right? And there's a lot— there's flexibility, there's strength, there's, you know, there's worry about sarcopenia for longevity. So there's actually— you clearly should do exercise, right?

Ben Greenfield [00:21:39]: And that's better, better mood, better mood, and the positive feedback cycle that— oh yeah, depression, all kinds of blood lactic acid out my eyeballs, therefore I'll I'll probably probably skip McDonald's breakfast McMuffin today and opt for something healthier.

Jason Fung [00:21:55]: Yeah. And clearly it's like even low-grade exercise. So when you have people who do sort of put in lots of steps and stuff, they do a lot better. So clearly there is a lot of health benefits, right? However, purely in terms of weight loss, it gets sold a little bit as, oh, you're burning off your calories and therefore you know, it's going to help you lose weight. The problem is that it actually doesn't. And this is relatively new research that, that if you— and now it doesn't apply to sort of people who are sort of exercise a lot, like hours a day sort of thing, which probably a lot of your audience is not in there, but people who think that, well, you know, I just exercise 3 times a week for 30 minutes each sort of thing, which is, you know, roughly what the guidelines are. And therefore I'm burning off calories. The thing is that there is a very interesting study where they looked at this, and as they increased exercise, what happened is that the total energy expenditure stayed relatively stable after sort of light to medium exercise.

Jason Fung [00:23:02]: So if you think about energy expenditure, you can think of it in sort of two buckets. There's actually more, but in two buckets, sort of voluntary stuff, which is exercise, and involuntary stuff, which is basal metabolic rate. There's also things like non-exercise, uh, what is it? Non-exercise activity thermogenesis. Yeah. The NEAT.

Ben Greenfield [00:23:23]: Yeah. The idea of like, like fidgeting, fidgeting.

Jason Fung [00:23:26]: Yeah.

Ben Greenfield [00:23:26]: I guess, I guess like thermal stress might fit in there, like being cold, things like that, that would burn extra calories.

Jason Fung [00:23:31]: And also the thermic energy of food, right? The, the, the energy it takes to burn, but those are relatively small. So if you think of it sort of simplistically, it's sort of exercise plus basal metabolic rate, which is your heart, your liver, your lung, your brain. And so as you increase your exercise, so you can get up to a certain point, and it's around 2,550 calories actually. And then as you increase exercise, your total energy expenditure actually doesn't go up past that. It actually plateaus because your body's metabolic rate actually starts to go down to compensate for the increase. And it's very interesting, and this is a constrained model. So there's the sort of additive model model of energy, which is that your basal metabolic rate stays the same and you simply add whatever exercise you have. But it doesn't seem like the human body actually does that.

Jason Fung [00:24:22]: It's a constrained model where you can get up to a certain number of calories, and then after that, the increase that you burn off in exercise, you take off in terms of metabolic rate. And the thing is that it's actually a good thing, right? So your body is becoming more efficient. Right? So your heart rate slows down, your blood pressure drops. These are all actually really good things, right?

Ben Greenfield [00:24:45]: It's basically like a thing like, I'm going to figure out a way to run these 3 miles with less pain. And so your body figures out, oh, I can have a lower heart rate if I move like this. I can be more efficient if I lean slightly forward. And the 3-mile run that might have burnt, I don't know, 300 calories 6 months ago when you first started working out might burn 200 6 months later.

Jason Fung [00:25:09]: Exactly. And it's a good thing from a survival standpoint, right? But not a good thing from a math standpoint, right? If you're just counting calories per— it's sort of like if you ever watch somebody who runs or something like that, or any kind of basketball or whatever, right? You watch the, the, the amateurs and they're just burning all kinds of— they're moving all over. There's all this extraneous movement. They're doing all this. Then you watch the people who have run like a lot and very well, and they're so graceful, right? Like, they're so efficient. There's no wasted movement. They're simply gliding. Like, you watch marathoners, and it doesn't even look like they're running fast, but they're actually running, you know, faster than I could run.

Jason Fung [00:25:49]: You know, they do 26 miles at a pace that I can't even do sort of 1 mile at, right? And it doesn't even look like it because they're so efficient at what they're doing, right? And their muscles, you know, they're very thin, the marathoners, right? And it's like, that's, that's the idea, right? You're just becoming so much more efficient. You're getting rid of all the extraneous movement. But it's more than that because it's like your, your, your heart rate is going down, right? So heart rate goes down into the 50s and 40s versus somebody who's not, you know, not in shape, who's like 80, 90, right? Your blood pressure is going down. You're calmer, right? You're far more focused, right? All this sort of extraneous sort of brain activity, which is just wasted movement and stuff, it's better. So it's a good thing from a, you know, from a survival standpoint, from a, you know, physiologic standpoint, but not a good thing if you're trying to burn calories. And that, that's sort of the myth is that you can simply burn off the calories and that that exercise will simply make up for, for that, right? Yeah.

Ben Greenfield [00:26:50]: Yeah. It's kind of an esoteric conundrum in a way because you could walk into a gym and see one person on a treadmill training for a sub-3 marathon. Who's doing every last thing they can technically to burn less calories, right? It's like lean forward, avoid heel strike, swing the arms in a certain way, breathe through the nose. And then you've got the person behind them on the Nautilus machine who's just punishing themselves trying to burn as many calories as possible because they visited Cheesecake Factory the night before. Yeah. And I guess it does say something to the idea— and I know a lot of trainers scoff at this notion, but I think there is something to it for weight loss— of metabolic confusion, right? Like using different exercise modalities regularly so the body never quite gets a chance to become efficient at one.

Jason Fung [00:27:42]: Yeah, yeah. I think there's probably something in that because you're always going to become more efficient at it, right? It's just like you watch somebody who plays a lot of golf and there's just no wasted movement at all, right?

Ben Greenfield [00:27:55]: Which means that I I burn, burn a lot of calories golfing.

Jason Fung [00:28:00]: A lot.

Ben Greenfield [00:28:01]: Hey, but what about— because I know people are thinking this, so I'm just going to name it. You hear two kind of theories in physiology. One is excess post-exercise oxygen consumption or EPOC based on the notion that if you do high-intensity interval training and you're really sucking wind, you are going to burn more calories the rest of the day to pay off that debt. And then not to throw too much at you here, you also hear the muscle explanation that if you lift weights, you're going to increase muscle mass. You're not only going to create a sink for extra glucose and increase insulin sensitivity, but you are also, based on the nature of having higher muscle mass, going to increase your metabolic rate because of the physiological need to carry and cool that muscle mass. How much of a wrench does that throw into the exercise myth idea here? How much of a wrench does that throw into the exercise myth idea here?

Jason Fung [00:29:07]: I think it actually probably— there probably is. I think it's probably true both of those things do happen, but it's actually quite complicated because then it gets conflated because there's differing effects on appetite as well, right? So you have exercise-induced anorexia because of course, if you're just talking about the muscle, the amount you're burning, that's one thing. But then if you're stimulating hunger after exercise, not during exercise, then you're going to compensate, right? And this is sort of the, you know, so that's why it's so complicated. That's why it's so difficult to like, because I think everybody's different. Some people will exercise and they'll do fine, but there's a lot of people who exercise, exercise, exercise, don't pay attention to their diet, or they think, well, I've earned this, right? And that just doesn't work, right? Like, if you really want to, like, you can't do that where you say, oh, I exercise an hour, I'm going to have some ice cream and cheesecake, right? That actually just really hard to work. But you get this exercise-induced anorexia, which is that when you're doing exercise, your appetite goes down. But after that, it actually tends to go up. And there's been studies in kids particularly where they look at like sort of light to medium exercise and they find that the overall weight, like overall calorie balance is actually positive after light or medium exercise, right? So that means that when you look at the total number of calories, like this is just math, like we're not just— so if you have somebody who does like, you know, half an hour of basketball or, you know, basketball practice or whatever, and you just simply take a look at the kids and see how much— what happens is that they're actually positive because they burn calories, but then afterwards they, you know, drank, you know, sugary drinks.

Jason Fung [00:30:54]: Yeah, exactly. And they're actually positive on average. They're positive. It's not until you get to sort of intensive exercise, sort of a couple hours of exercise, that it actually starts to go the other way and you're negative balance. So it's a complicated field, but, you know, the point is, again, It's more complicated than this very simplistic idea of calories in, calories out. Let's just look at, you know, what you're eating and how you're exercising, because that completely ignores the effect of the metabolic rate. And the other thing it really affects— what it ignores is the effect of hunger, because again, how much you eat depends on how hungry you are. That's sort of a base, you know, it's, it's, it's It's— everybody knows that.

Jason Fung [00:31:39]: So why are we not talking about hunger, how— what it is, how it's controlled and all that? Because that's going to determine how much you eat. Obviously, if you're hungry, then you're going to eat more. If you're not hungry, you're going to eat less, right? So that's going to play a huge role, right?

Ben Greenfield [00:31:54]: Yeah. I think that, you know, again, there's so many variables here, but when you talk about hypercompensation, it also makes me think about this idea of cold plunging. Or cold thermogenesis. And depending on, you know, what data you look at, what claims you look at, people will say tens of percentage points up to even hundreds of percentage points of an increase in metabolic rate in response to being cold. And yet a study last year showed somewhere in the range of 200 to 300 extra calories being eaten by people who did cryotherapy or cold thermogenesis. And it kind kind of, of evened out or even exceeded what they were burning. And I agree, like if you freaking get hungry and a nice, I don't know, warm plate of scrambled eggs tastes pretty good after you've been cold plunging and maybe adding an extra 25% of cheese and eggs in the tortilla wrap on top of that makes it even better. I think that if you look at the exercise piece, the main takeaway for me is that that if you're just exercising to lose weight, then long-term, you're becoming more efficient at that exercise, your body adapts from a survival standpoint to burn less calories.

Ben Greenfield [00:33:14]: And so, you need to be aware of that. You need to be aware of the hypercompensation piece. And then, this last thing, I think it can be a little bit psychological as well, Jason, and also physiological. A hard workout. I was actually recently speaking with Dr. Andrew Koutnik about this. Lactate can serve as an alternative fuel source for the brain, as can the ketone bodies from the burning of fat if that exercise is done in a fasted state. And that alternate fuel source for the brain can actually quell some of the post-exercise hunger.

Ben Greenfield [00:33:49]: And it seems a little bit paradoxical, but you're actually less hungry. I think a lot of people, including myself, have experienced this. You're less hungry after a hard workout that generates lactic acid than than you are after a fed workout or an easy workout.

Jason Fung [00:34:05]: Yeah, I mean, I noticed that same thing too, right? If you're doing these, you know, high-intensity things, you just don't feel that hungry. But if you do one of these like easy runs or, you know, the whole zone 2 thing, oh, I'm just gonna do that, which was popular like years ago, cardio, right? And, and like, uh, you know, those exercise step classes and all that sort of stuff, It was all like this low-intensity stuff and it wasn't— your appetite did never go down the same way, right? When you're like hurting, right? You're hurting at it. Like your muscles are sore. You're really— it's like you don't really feel like eating. So that's probably true. I would tend to agree with that.

Ben Greenfield [00:34:47]: Yeah. I would say in the book of the 3 types of hunger that you discuss, homeostatic hunger, hedonic hunger, and conditioned hunger. Selfishly, I'm most interested in this homeostatic hunger piece. But real quick, what are the 3 types of hunger?

Jason Fung [00:35:06]: Yeah, so hunger is actually— we all think about sort of the physical hunger, which is the homeostatic hunger. So there's 3 different types, at least 3. There's probably more. But so if you think about why we eat, right, you eat because you're hungry. There are different types of hunger. Because if you think about why we eat, there's the sort of stomach is growling, you're really, you know, food looks really good to you. That's the hunger we all think about. And that's homeostatic hunger.

Jason Fung [00:35:36]: It's driven predominantly by hormones, right? So it's not just that you haven't eaten in a while and therefore you're hungry, right? Because for example, like exercise-induced anorexia, You could not eat for a long time, but if you're exercising, you're still not going to get hungry, right? Like if you're in the middle of a hard, you know, basketball game or something, you're not like, ooh, you know, I'm really hungry, right? You're too, you know, both psychologically but physically, there's no hunger there, right? Because you're exercising. So it's interesting because people think that, oh, if you haven't eaten in a while, you're hungry, but it's not. It's all determined by hormones. And the clearest example of that is something like Ozempic, which stimulates the GLP-1 system. And of course, you could not eat for days and still not be hungry. Why? Because you're taking the Ozempic, which stimulates GLP-1, which is one of the satiety hormones, which sort of turns off all that hunger. And there's a ton of these hormones. And there's also brain areas like the lateral hypothalamus, the, you know, medial hypothalamus.

Jason Fung [00:36:37]: So, you know, in the '40s, they talked about, you know, you could make lesions in the brains of rats and make them fat or make them skinny. Right. And you know why? They were either hungry or not, not hungry, right? So that's homeostatic hunger. But that's not the only reason we eat. And there's a whole, um, two other things. The hedonic hunger is actually— hedonic is a word that means relating to pleasure, and you eat because it makes you feel better or it makes you feel good, right? And that's a huge reason why people eat these days. If you think about dessert, that's practically all the only reason you eat dessert, because you've already eaten your meal, you're satisfied, your homeostatic satiety hunger, yet you're still going for that ice cream and pie because it looks so good and you eat it, you know, you're going to feel good, right? Because of the sugar and, you know, all that sort of stuff. And that's what the notion of comfort food is, right?

Ben Greenfield [00:37:32]: So I'm stuffed. Oh, hey, look at the dessert menu.

Jason Fung [00:37:35]: Yeah, that's right. Hey, look, I could use that. But it's true. It's— we all know it happens. So why are we not talking about it, right? Because it can be a problem. That is, If you are overeating, then it's possible that you're not overeating because of your homeostatic hunger. It's because you have— you're like an emotional eater, or you have a comfort food. So comfort food is a food you eat to make you feel better, right? So the classic example is like you break up with your boyfriend or girlfriend and you eat a whole tub of ice cream, right? And that's not because you're hungry.

Jason Fung [00:38:08]: It's because of the— you want to feel better. That's the comfort food. And you think about comfort foods, there's all kinds of things, apple pie and ice cream. Cream and mac and cheese and all these things, mostly ultra-processed foods. And it can tip into— so, so hedonic hunger is very important because I actually think it plays a larger and larger role in sort of the obesity epidemic, because ultra-processed foods are notoriously bad for hedonic hunger. They stimulate a lot of hedonic hunger, and the reason is because they're designed to stimulate that hedonic hunger. So if you're a food company, you want to sell food and make money. So the best way to sell food is make food that is sort of makes you feel good, right? So there's tons of ways that they increase the hedonic hunger.

Jason Fung [00:39:01]: You know, there's texturizers and emulsifiers. There's artificial sweeteners and artificial flavors. There's, you know, you get the right mouthfeel, you get the right percentage of salt and fat and sugar. Like there's a whole science behind this, right? And it hasn't— it's been developed so that you buy more, which means the only way— reason you'll buy more is because you're going to eat more, which is good for their bottom line.

Ben Greenfield [00:39:24]: Yeah, yeah. The down economy, fortunately, uh, we've kicked that horse to death with my audience, and they know to avoid hyperpalatable foods and eat in a more mindful state and chew thoroughly. Like, they kind of know that part pretty well, um, fortunately. I don't think we need to spend a lot of time on, like, don't eat ultra-processed foods or be aware of highly hedonic foods. And I do want to get into conditioned hunger if we have time, where things like where you live or who you're with might affect your weight. That whole, like, if you have a bunch of overweight friends, you might be overweight. But from the homeostatic, like, if I want to focus on one thing in the time that we have, I want to talk a little bit more about this homeostatic piece because we talked about this body fat thermostat and how your body can adjust up or down the number of calories you burn. Is there a way to somehow adjust that or use the fact that there is one to our advantage when it.

Jason Fung [00:40:20]: Comes to— Oh, absolutely. So the way that our body is— so homeostasis is basically a core biological principle. So if you, you set sort of a preferred state, and if you go higher, you adjust, you know, your body will activate mechanisms to bring it back. So it's like a room thermostat. If you think about your thermostat in your room, you set it at room temperature. If it gets too hot, it's going to activate the air conditioning to cool it down. If it gets too cold, it's going to activate the heat to bring it up. Either way, despite varying external conditions, you maintain that normal set set point.

Jason Fung [00:40:58]: And that's homeostasis, right? And it's not just true for one thing, it's virtually every system that is mission critical in the body is— has a homeostatic mechanism. So your body temperature, for example, if you get too hot, you're going to sweat. If you get too cold, you're going to shiver, right? Body water, if you drink a lot of water, you're going to pee it out. If you don't drink a lot of water, you're not going to pee it out. You're even going to stop sweating and stop, you know, making tears and all this sort of stuff, right? Salt— if you eat a lot of salt, you're going to pee it out. If you don't eat a lot of salt, you're going to reclaim all that salt from your urine. So every single system in the body— if you don't get enough oxygen, you're going to hyperventilate. So people with COPD, they breathe very fast.

Jason Fung [00:41:41]: Why? Because they need to get more oxygen in. If you have too much carbon dioxide, people will hyperventilate. So every single system in the body is controlled by homeostasis, because otherwise You die, right? It's, it's, it's simple as that. And it's the same with body fat. So there's this argument that I find really stupid that we're, we're, we're, we're designed to store calories. And therefore, because calories are easy to get, we store a lot of calories. And so we're doomed to get fat. And it's like, okay, that makes zero sense, right? Think about a wild animal, for example.

Jason Fung [00:42:17]: If you're a predator and you're morbidly obese, You will never catch anything ever again. So you're going to die. If you're a prey animal, like a deer or a rabbit, and you're morbidly obese, you're going to die because you're going to get caught. So obviously the amount of fat you carry is very important. If you carry too little body fat, you're not going to survive the winter. So you're going to die. So the human body is no different. It's, it's, it always sets that body fat level to its preferred amount.

Jason Fung [00:42:46]: Yes, there's variation within that amount, but you shouldn't go too high or too low. You know, you look at times in history when food was plentiful, right? If you look at the ancient story of Joseph where there are 7 years of plenty, they don't describe an ancient epidemic of morbid obesity because our bodies are not like that. And that's been proven over and over again. So if you take somebody and you force feed them, and that's been done, right? You force feed them, their metabolic rate goes up. So you make them gain 20 pounds, right? What happens is that their body starts starts burning off 500, 600 extra calories a day when you stop. So you can, you can get them up, right? You can get them, force them up. And they've done that experimentally. They actually had to feed these people like 8,000, 10,000 calories a day to get them up 10% of their body weight.

Jason Fung [00:43:34]: It was a massive amount.

Ben Greenfield [00:43:36]: Sounds like me when I was bodybuilding in college.

Jason Fung [00:43:39]: Yeah, you're just pounding it down.

Ben Greenfield [00:43:41]: I laid on the couch eating Yeah, yeah.

Jason Fung [00:43:44]: And it's crazy because it was very hard to get these people to gain that much weight. But the minute you stop that experiment, what happened? They actually all lost that weight. Why? Because their body fat— you had pushed them above their body fat thermostat, so their hunger just got killed for weeks. And that's what leptin does, right? It kills your appetite. So then they went back down. So the whole point is that if you— if you're— if your body weight is— if you're overweight, then that doesn't mean that calorie is It's, you know, calories in was greater than calories out, but that wasn't the controlling factor, right? It was controlled by this body fat thermostat. Just like if you go into a room that's too hot, you don't go, well, let me calculate heat in minus heat out and calculate all the sources of heat in and all the sources of heat out, right? You say, why did somebody set that thermostat so high? And the other thing is, what are you gonna do about it? Well, you're gonna just crank that thermostat down. You don't need to sort of, kind of futz around with heat in minus heat out.

Jason Fung [00:44:41]: So, the body fat thermostat's the same thing. You set that weight, and we all know this is true because you look at different body types, people are set different ways, right? Some people are, you know, from the minute they're born, they're slightly heavy. And there are people who are born, they're always on the thin side. That's that body fat thermostat. But there are certain hormones that push it up and certain hormones that push it down. And that's the whole point. If you look at insulin, You give somebody insulin, they gain weight. That means you've pushed that thermostat higher.

Jason Fung [00:45:10]: It's not because you took away their willpower. If you give them cortisol, which is that stress hormone, you push that thermostat up. If you give them Ozempic, which stimulates GLP-1, or Mounjaro, which stimulates both GLP-1 and GIP, you push that thermostat down. But there's other examples. Sympathetic tone, for example, is actually something— so sympathetic tone is a part of the autonomic nervous system, which is— there's two parts. There's the sort of sympathetic tone, which is the fight-or-flight response, and there's the parasympathetic tone, which is the sort of rest and relaxation mode, right? So when you stimulate sympathetic tone, you make people lose weight. You push that thermostat down, right? And there's plenty of examples. If you look at the, uh, nicotine, for example, nicotine causes people to lose weight.

Jason Fung [00:45:58]: It absolutely does. And it's because of the increase in sympathetic stimulation of the sympathetic nervous system which decreases their appetite so they lose weight. There's an old drug called amphetamine, which is— used to be called speed. So in the '60s, it was very popular for weight loss. There's a drug called Fen-Phen, which is phenfluramine phenteramine, which was again taken off the market in the '90s because of heart problems.

Ben Greenfield [00:46:25]: Yeah, and that, that's what I wanted to clarify with nicotine. Like, if you look at sympathetic activators for weight loss, Yes, they would work, but also often due to the vasoconstrictive effect. You know, this is even something you see happen with nicotine. You have to ask yourself whether the cardiovascular stress is worth the appetite suppression or if you may want to choose other strategies.

Jason Fung [00:46:49]: Yeah, it never really was. That's why nobody does it anymore. But it's interesting when you actually read old accounts of amphetamine or speed, uh, so it was prescribed as a weight loss drug. And what it did is it doesn't restrict calories, right? It decreased your appetite. And that's so important because that's what it— that's how your body adjusts your fat thermostat, right? Your fat thermostat's like, goes up or down. You adjust it with the hormone. If your body finds that you're over that limit, then it's going to adjust hunger or satiety to make you either hungry or not hungry so that you get to that proper weight, right? So with amphetamines, as you drive that thermostat down and your weight is still up, it's going to kill your appetite, right? And that's what speed does. The old— you know, there's all these things.

Ben Greenfield [00:47:39]: So I have a cigarette and some meth with your kale, uh, chocolate chip you know. cookie.

Jason Fung [00:47:43]: Hey, but it's so bad for you in other ways, right?

Ben Greenfield [00:47:48]: Yeah, we're not endorsing that. Yeah, so One lightbulb moment I had when reading your book that I think might be a pattern interrupt for people, I believe it was when you discussed vanishing calorie density, was this idea that a lot of nutritionists and dietitians will tell people, eat these nutrient-dense foods, right? Like stay satiated with steak and almond butter and a handful of macadamia nuts. You point out the fact that that might possibly be the opposite of what you want to do.

Jason Fung [00:48:20]: Yeah, I mean, really, I mean, it's, it's so vanishing caloric, um, uh, sorry.

Ben Greenfield [00:48:27]: Vanishing caloric, vanishing calorie density. You know, where is it? It's on, it's on page— was it page 70? Yeah, page, page 70, uh, about the, you know, the cheese, the cheese puff, the potato chip, the fluffy French fry. And then like even the idea of like squishing and cooking and steaming and mashing your vegetables like maybe going after bulk and what you call— you call them heavy foods, right? Heavy foods to maintain satiation, leafy green vegetables, berries, beans, whole oats, cauliflower, broccoli. For me, that was kind of an important reminder because I've even told people, you know, like Weston A. Price diet is great. You know, it's a fermented dairy sourdough bread and nut butters and— well, I don't know how much nut butter they do, but, you know, organs and grass-fed meats. But sometimes for weight loss, you might want to be a little, a little more sparse.

Jason Fung [00:49:28]: Yeah, you want to be— you want to make it hard to eat, right? So the vanishing caloric density is a concept where if something sort of just melts in your mouth, then you feel like you haven't eaten anything. So even though there's calories, there's really no satiety at all. So the cheese puff or the fluffy French fry, it just sort of melts in your mouth. So you feel like you haven't even eaten it. And I always joke sometimes with my wife, like something is, it's, it's, uh, it looks light, right? They're like, oh, it's light, right? But it might be a chocolate mousse or something. It's like, it looks like, right? It's not actually, it's got tons of calories. But the point is that you want something, something hard to chew, for example. So if you chew it and chew it and chew it, that sends a signal to your brain that, you know, hey, this is something that we're filling up, right? We need to stop eating soon, right? So the vanishing caloric density, if you have something that's very dense and just goes right down and that's it, like, that's not actually that good for you, right? Something heavy, something bulky is good, right? You know, that's why vegetables in general are very good because they're actually nutrient sparse, right? There's a lot of volume like cauliflower or broccoli.

Jason Fung [00:50:42]: You look at the number of calories in it, it's not much, but it's huge, right?

Ben Greenfield [00:50:47]: I was at the Ancestral Health Symposium one year and this guy gave a you talk, know, and he like pulled up kale and blueberries and all these so-called superfoods, and then he pulled up liver and it just like kicked the ass of all of these other foods. However, the other foods, despite having lower nutrient density, have more volume.

Jason Fung [00:51:07]: Yeah, yeah. So there's a balance there for sure. But I think where it plays a role is sometimes in the processed foods, one of the ways that it's really, really bad for you is that they're very easy to chew. So through texturizers and emulsifiers and all this sort of stuff with mouthfeel and stuff, when you eat ultra-processed foods, it actually goes down really fast. So there's actually an interesting study about comparing apple slices to applesauce. So applesauce, they made it by baking the apple and then pureeing it. By pureeing it. But remember, they haven't added or subtracted anything.

Jason Fung [00:51:42]: It's actually the exact same apple. You've just changed it by cooking it differently. But by doing that, you actually change it significantly because the gastric transit time, like how long the apple stays in the stomach, is much higher.

Ben Greenfield [00:51:59]: So, so, so this is interesting. So now we took the cookie salmon analogy and now we're saying salmon and salmon or cookies and cookies. Cookies. Let's just say cookies. Why not? Apples are boring. So, what you're saying is if I'm eating Oreos and I take 10 of them and I put them in a blender, maybe with some water to keep them calorically equivalent, and I drink that smoothie and then I eat 10 cookies, my satiety response and possibly my weight gain or loss response is going to be different between equivalent Oreo cookies blended versus eaten?

Jason Fung [00:52:33]: Yeah, because it's easier to eat, so therefore it gets digested easier. Because when you're eating the cookies and you're chewing them and stuff, it's got to go down into the stomach, then the stomach's got to churn them up and so on, right? When it's hard, when it's bulky, right, when it's more difficult, then it goes through slower. So by blending it, you actually sort of pre-digest this. It's like adult baby food, right? You've pre-digested this food to make it easier to absorb. But the easier absorption means that it goes through faster, which gives you a much higher spiking glucose and insulin and so on. So even if you compare two foods, you can actually change the measurable hormonal response in those foods. Actually, there's lots of different ways. And that's, that's what I actually found really fascinating about the, you know, when I was doing some of the research for the book, it's like, man, like these simple changes and it sometimes works the other way.

Jason Fung [00:53:24]: So when you actually blend seeded fruits, you actually get a benefit.

Ben Greenfield [00:53:29]: It. Yeah, I remember that study came out and that was kind of a paradox for a lot of people. They're like, wait, you mean if, 'cause a lot of people think, well, if I make a smoothie, I'm getting a higher blood glucose response. What was the thing with the seeded fruits? Was it better exposure to the anthocyanins and polyphenols?

Jason Fung [00:53:45]: It was the polyphenol. So, there was a study, they used passion fruit and mango, right? So, mango is, you know, they measured mango, then they measured mango smoothie, which was worse, right? So, as you expect, effect. But then they used sort of a mango passion fruit smoothie. And what happens is when you blend the seeds, you actually release all of the fiber and polyphenols. So you actually slow down absorption. So you actually had less glucose effect and less— and so strawberries had that effect and passion fruit and some of these other seeded fruits, which I thought was really interesting because I totally thought it'd go the other way.

Ben Greenfield [00:54:22]: I know, I thought too. And I was even guilty of saying a few times in my life, like, yeah, if you blend or juice a fruit, there's a significant difference in the glycemic response. And it seems like that gets kind of balanced out if it's whole fruit.

Jason Fung [00:54:36]: I mean, it's still true for some things, right? But not seeded fruits like apples. That was a classic, right? Apples versus applesauce versus apple juice. Yeah, right. Very, very different. Like apple juice plus added— if you take the apple juice, add fiber back so that they're equivalent in terms of calories and carbs and all that sort of stuff, it's still way worse for you, right? Same as applesauce. It's actually much higher glycemic index. Index. But there's other ways, like the food timing, the, the timing of your meals.

Jason Fung [00:55:02]: So early versus late, eating the carbs first versus eating carbs last, eating naked carbohydrates, vinegar. Vinegar was actually fascinating. I thought that was really, really interesting.

Ben Greenfield [00:55:12]: That's an interesting one. Yeah, I, I still love the apple cider vinegar trick for lowering the glycemic response to a meal. But back to the applesauce thing, not that anybody would do this, but like if you made your applesauce and kept the skins and the seeds in there, it sounds like it might actually be a little bit closer to just eating apples.

Jason Fung [00:55:30]: Yeah, yeah. And it's the release of all the fiber that's in it. It starts to bind it, right? So then it doesn't get absorbed as quickly. So even though they're the exact same foods, they're— the way you, the way you cook them and make them changes their digestion, right? So remember, it's food, digestion, absorption, hormones, then weight gain.. So everywhere along this sort of pathway, you can actually influence that. Right. And, you know, in terms of hormones, you know, there's a, there's a whackload of hormones too, right? There's a whole lot. I mean, each path, each step, I think I list at least 10 different ways that you can alter it.

Jason Fung [00:56:08]: Resistant starch is actually another really, really interesting way to change the absorption as well. And that, that I thought was relatively You know, pretty powerful too.

Ben Greenfield [00:56:20]: It's kind of nice too, because if I cook my rice and have it for dinner, usually I'm doing something active before dinner. I'm in a somewhat insulin-sensitive state. I like some carbs with dinner, but then if there's some leftover and I have that cooled for lunch the next day when I'm perhaps in a less active state, I have a lower glycemic response and better satiety. Yeah, the resistant starch piece is pretty cool. You've brought up Ozempic and GLP agonists, it's no secret, of course, they're effective at reducing hunger. What's your take on the idea that if you get on them, you're kind of like on them because if you get off of them, you're going to have this rebound in hunger? And just to couch this, like, I'm torn between the idea that you can use them like training wheels to learn what not feeling hungry is like, and then when you stop using them, you've kind of like understood how to control your appetite. And then there's the opposite scenario, which is, no, you're going to get huge yo-yo weight gain because as soon as you get off them, your hunger just like comes back like a tiger.

Jason Fung [00:57:24]: I think it's, you know, it all depends. And that's why I'm not against these GLP-1s, because for the most part, like the idea is that you have to know how to manage hunger. And there's lots of different ways, right? Because we all think it's about calories, but it's actually to so much more than calories, right? Like, you know, the example, like if you eat a 3-egg omelet with 800 calories, you know, vegetable omelet, it keeps you full for a while if you eat it. If you have an 800-calorie Frappuccino, you're hungry like 10 minutes later, right? So they're not equivalent. So how do you manage the hunger? And that's where, you know, a lot of stuff you talk about, like the, you know, the proteins and the unprocessed foods and getting rid of, you know, the resistant starches and all that sort of stuff, that's going to play a role. But you have to that, learn right? And that's why it's important. We talk a lot about calories and not a lot about how to, you know, deal with hunger. I feel like with the protein sort of renaissance, that's sort of getting a little bit of play.

Jason Fung [00:58:23]: But the whole idea is that most people who go on these drugs don't actually start learning about how to manage that hunger, right? What's the differences between the foods? Because everybody stops at calories. Nobody goes on and says, well, what about this hormone, this hormone? What about hunger? What about hedonic hunger? What about hunger? conditioned Emotion hunger, all this other stuff, right? So you could use it as training wheels, but the reality is that when you go see your doctor, you get that prescription of Ozempic, that's it. There's no more teaching, right? So therefore, in virtually like 99% of cases, when you take away that training wheel, those people just fall flat on their face because they never actually learned to ride that bicycle, right? Right.

Ben Greenfield [00:59:08]: So no more teaching unless you listen to the show. Read the book. Some people are self-directed, I'll admit. Hey, we're running up against time, but just for the sake of fun and education, if you were to share your top strategy for keeping hunger at bay, I'd be curious to know what it is, whether nutrition or lifestyle-based. I'm going to say mine, and my apologies if I steal yours and you got to think of another one. Mine is to keep myself busy because I'll have some days where I fast or a couple times I've had to get a colonoscopy and you don't eat the day before. And so, for me, I will fill up my schedule if I know I want to eat less with a lot of activities, even on an airplane, right? I've got my articles, I've got my books, I've got the 2 things I want to churn out on my laptop. I find distraction and just basically keeping myself busy with other things to be the most effective.

Ben Greenfield [01:00:11]: I suppose maybe the one that might beat it would be like injecting a GLP, which I actually do now before a long day of travel. I have a bottle of retatrutide in my refrigerator. It's lasted me like 2 months, but I do like a little baby dose before I travel and I just don't think about eating, like, during my entire trip, which is kind of nice because the options are limited anyways. Um, what's, uh, what's your top tactic, or one of them?

Jason Fung [01:00:38]: Um, I mean, I think that that certainly is a great one, uh, for most people. I think, um, you know, and I have sort of in the book, I have sort of 3 golden rules and sort of 50 weight loss tips, but I think getting rid of the ultra-processed foods is like the biggest contributor. One, because it's like sort of 70% of the American diet. And I think you've been sort of on the forefront of this for a long time, right? But the ultra-processed foods are bad for you in so many ways, but mostly is that they create a lot of hunger, both, you know, and it cuts across all types of hunger. So both the homeostatic hunger, because they stimulate a lot of insulin, they don't stimulate a lot of less satiety like GLP-1s, the baroreceptors in the stomach, the, you know, the sympathetic tone. So they create a lot of this homeostatic hunger, but they also create a lot of the hedonic hunger, right? Because of the way they're designed, right? With texturizers, emulsifiers, artificial sweeteners, artificial fats, all this artificial stuff. And then the conditioned hunger is that sort of habit-containing piece where you, you, you, you get used to eating the ultra-processed foods, like in the car, in front of the TV, when you watch a movie, when you watch sports, when you, you know, read a book, everything is food, food, food, food, food. And become very soon you simply sort of, uh, it becomes so second nature that you don't even notice it, but you're creating a lot of homeostatic hunger, a lot of hedonic hunger, a lot of conditioned hunger.

Jason Fung [01:02:08]: And that's why when you see countries that have a lot less ultra-processed foods, like Italy, for example, like Italians love food, right? They talk about it constantly, but the actual incidence of obesity is so much lower. And you look and you say, what's the difference, right? They're eating pasta, right? Lots of refined grains there. Well, the number of ultra-processed foods in their diet is like 25% versus 70%. Right. And to me, that's a huge thing. You take that Italian, plop them into like New York City, and all of a sudden with the ultra-processed diet, like everything gets replaced. Right. And all of a sudden you've got like Olive Garden.

Jason Fung [01:02:47]: Yeah.

Ben Greenfield [01:02:48]: Yeah, I agree. Well, gosh, like we cracked barely the surface of this book, The Hunger Code. BenGreenfieldLife.com/HungerCode. /hungercode is where the show notes are. I'll include a link to a really fascinating fasting podcast I did with Jason as well. But, check out the book. It's got a lot more in there. Like Jason said, tons of extra tips, BenGreenfieldLife.com/hungercode.

Ben Greenfield [01:03:15]: Jason, thanks so much for doing this.

Jason Fung [01:03:17]: Thanks so much, Ben. It's great, great talking to you.

Ben Greenfield [01:03:20]: Alright, folks. Have an incredible week.

Ben Greenfield [01:03:22]: To discover even More tips, tricks, hacks, and content to become the most complete.

Ben Greenfield [01:03:27]: Boundless version of you, visit BenGreenfieldLife.com.

Ben Greenfield [01:03:38]: In compliance with the FTC guidelines, please assume the following about links and posts on this site. Most of the links going to products are often affiliate links of which I receive a small commission from sales of certain certain items, but the price is the same for you, and sometimes I even get to share a unique and somewhat significant discount with you. In some cases, I might also be an investor in a company I mention. I'm the founder, for example, of Kion LLC, the makers of Kion-branded supplements and products, which I talk about quite a bit. Regardless of the relationship, if I post or talk about an affiliate link to a product, it is indeed something I personally use, I support and with full authenticity and transparency recommend in good conscience. I personally vet each and every product that I talk about. My first priority is providing valuable information and resources to you that help you positively optimize your mind, body, and spirit. And I'll only ever link to products or resources, affiliate or otherwise, that fit within this purpose.

Ben Greenfield [01:04:38]: So, there's your fancy legal disclaimer.

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Ben Greenfield

Ben Greenfield is a health consultant, speaker, and New York Times bestselling author of a wide variety of books.

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Thoughts on Reset Your Body’s Metabolism for FASTER Weight Loss & LESS Hunger In An Era Of Ultraprocessed Foods, With Dr. Jason Fung.

One Response

  1. This is such a thought-provoking conversation. The deep dive with Jason Fung really challenges the oversimplified “calories in, calories out” narrative and adds important nuance around hormones, insulin, leptin, and the body’s fat “set point.”

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