Everything You Know About NUTRITION Is WRONG! Here’s Why | Herman Pontzer

If you assign people a diet for a year, and you say you're going to have a high carb diet, and you're going to have a high fat diet, and I watch you for a year, the weight change is the same, and uh you can lose weight on either of the diets, depending on how well you stuck to the calorie counts, not the carb counts. Herman Pontzer, PhD, welcome to the show. Yeah, glad to be here. Dude, I'm really excited. Your book Burn seems uh designed to challenge what people think they know about nutrition, and I have the first sort of controversy of my career back at Quest was around a calorie is not a calorie. Mhm. And we put out the show called The Calorie Myth, and people went ballistic. And I'm talking, you can't imagine how surprised I was. I was like, that's just like the 101, that's the non-controversial one, and people went crazy. Anyway, I formulate my hypothesis around calories and that a calorie isn't just a calorie, and that there's hormonal signaling going on, and that the body is basically far more complex than just calories in, calories out, and but recognizing that that's a very controversial stance. Um what in So, you've studied the Hadza, and we can get into that, but I'm actually far more curious about why a calorie is just a calorie, and why if we want to burn fat that we have to think about a different mechanism than that hormonal signaling, than the insulin response, things that I thought we could take for granted. Yeah, so I don't think anybody who views, you know, who works in the the world of of measuring calories like I do, uh thinks that all calories are equal in the way that that sometimes it's implied. So, there's this, you know, there's there's kind of straw manning that goes on on both sides of this argument. And one version of it is that um when I say something like, well, to gain weight or lose weight, it's all about the calories you consume versus the calories you burn off, that gets framed as, "Oh, you're saying that if the type of food doesn't matter, right? Or that all foods are the same or like 100 calories of potato chips is the same as 100 calories of broccoli." And I don't think anybody who works in physiology really thinks that in terms of the effect it has on your body. Um those 100 calories will in the end have the same effect on your weight if that's if if that's all you ate, right? But um you know, the fiber in the broccoli and for that matter the the flavorings in the potato chips are going to have different effects on the way that they affect your brain and on hunger satiety signaling. So, I don't think um you know, the the all calories are equal thing I think can't gets caricatured a bit into thinking that that's all we care about. Um I don't think that's all we care about. On the other side of it, I think, you know, when people say, "Well, if if you're saying that all calories aren't equal, then you're basically agreeing with the idea that it's all carbs and insulin." Right? And you know, if if we understand that insulin is this really important hormone that has effects all over the body, and insulin is is really important for getting glucose into your fat cells, um you know, turning glucose into fat, then well, then we must be in agreement that insulin really is important and it's all about insulin and and and the fat cell, right? And well, well, hold on a second now. Insulin and its effects are of course huge and systemic and all throughout the body, but that's not the only thing that's going on when you eat. There's tons of signaling that's happening. Um there's hunger satiety signaling that's happening in the brain. Some of that's mediated by insulin, but actually a lot of it's not. Um you could have Insulin can have its job. Nobody disagrees with this about getting fuel out of your blood and into your fat cells and packing your fat cells full of fat. Insulin can have that job and still not be driving the bus when it comes to weight gain and weight loss, right? So, I think we have to kind of unpack here and and sort of agree to how we're going to think about this to have a really fruitful conversation. Yeah, no, I'm with you on that. So, the place that I want to start is to build up the two different arguments that are going head-to-head and then why they matter and then we'll get in there and begin to tease this out and I'm going to push back on things based on what I have come to believe. So, here's how I see the two arguments. There's argument number one is, "Hey, the reason that we have the obesity epidemic here in the West is because people are overeating calories." And the second law of thermodynamics is such that energy cannot just disappear. It's, you know, going to stay. So, sun hits the plant, animal eats the plant, animal grows, we kill animal, we eat it or we eat the plant, but we're basically just turning sunlight into cells for our body. And if you intake too much of that energy in the form of kilocalories, as you very accurately describe in the book, if you eat too many of those, then no matter what, you are going to put on weight and there is this extraordinary mechanism in the body where it's really going to make sure that whether you lay on a couch all day or whether you're running marathons all day, your energy output is basically the same, which seems impossible to believe, but you have some incredible [laughter] data around that. And so, we'll get into the Hadza. So, that's argument number one. It goes head-to-head with this second argument, which is, "Come on, man. Like, what if I'm eating a Twinkie, that is so different in terms of my bodily response than if I'm eating broccoli. And so, you can't just say that a calorie is a calorie. I'm not going to get morbidly obese by overeating broccoli. I'm going to get morbidly obese because there's all these other things like sugar being sort of the biggest villain that are in these foods and it's really the sugar that's the problem even more than the overeating. And they will grant that sugar probably compels you to eat more than you would otherwise, but really sugar in and of itself is a problem. And so it's a calorie is not really just a calorie. So we get these things that come colliding in your book. And I think now starting with the the thing that you set out to research with the Hadza and that whole framing is the right place to start. Like I want to get into why did you want to study energy expenditure and why did you think they were the right people to study? Yeah, well so I wanted to study energy expenditure because that's where the rubber hits the road in evolutionary biology. And I'm an evolutionary biologist that studies humans. Um and you know life is a game of turning energy into kids. And so Evolution [laughter] is all about that. Nice. Evolution is all about that. Uh you know, strategies, behavioral strategies, physiological strategies that do that better are favored by natural selection. And so you know, that that's really energy is really where it's at when you're thinking about the kind of the currency of of evolution and the currency of biology. Um humans evolved as hunter-gatherers. Uh the human lineage has been hunting and gathering for over 2 million years. Our species only shows up about 300,000 years ago. So we're a hunting and gathering species from a hunting and gathering stock. Uh and you know, in the same way that if I want to understand a bear or a dolphin or any species of animal, I want to understand it in its ecological context in the context in which it evolved. I don't want to study it in a lab necessarily. I don't want to study it in a zoo. I want to study it where it evolved. Um if for us that lifestyle is hunting and gathering. So I want to find communities that are still doing it. Um and they allow us to ask the question, how does your body function in in its sort of ecological nor you know, natural setting. Uh and so there aren't many populations that do that anymore. So one of them is the hunt the Hadza community in northern Tanzania. And we went to measure energy expenditure there and we thought that we would find cuz they're really physically active as you can imagine hunting and gathering get men get 19,000 steps a day, women get 13,000 steps a day. Um we thought that they would have sky-high energy expenditures. And in fact, they don't. Uh they have the same daily energy expenditure as your typical American, your typical European, your typical industrialized uh relatively sedentary human. So that was the first hint that uh this isn't working the way that that I that I was taught, you know, that that I in this sort of simple version of of how metabolism is supposed to work. So that you get this confounding mystery. You guys are using would we call it the the gold standard of caloric uh expenditure? A brief snapshot of what that is, I think, would help people. Sure. So you drink some I it's called the doubly labeled water technique. You drink some water where the you know, water's H2O. You drink some of the water you drink some water where some of the H's are deuterium and some of the O's are an isotope, a different form of oxygen. And we can use those as tracers. And the hydrogen isotope tracer becomes a tracer of water throughput through your body. The oxygen uh isotope becomes a tracer of of both water and the CO2 that you produce when you burn calories. And so if we if we subtract the deuterium signal from the oxygen signal, the only thing that's left is the CO2 you produce every day. So it's a precise measure of carbon dioxide produced over the course of we do these experiments over about 7 to 10 days. So it's a pretty good, you know, snapshot of your life, a 7 to 10-day long snapshot of your life and how much carbon dioxide you produced. And you can only produce CO2 burning calories and you can't, you know, so that it's a really good signal of of calorie burn. Um and it's the gold standard for anybody outside of a laboratory. And when we talk about calorie burn, you mentioned in the book that you don't think most people understand that you're exhaling most of the calories that you burn versus other things that we probably think about it as, you know, using your muscles or whatever. But it's uh it's actually just part of the the metabolic rate of all of your cells as manifested by exhaling the uh carbon dioxide. And we start getting this data back and we're saying, "Wait a second. They're not using more energy." What's your first leap as to what how that could be possible? It doesn't seem possible. well, no. The So, the first reaction was we I I don't know what your language rules are what that we screwed up. Uh or the first expect I mean, that that's the first a good scientist always assumes that they screwed up when you get funny results. Uh and I you know, I I I think we were we're pretty careful about that. So, the first thing we did is we we actually use a whole a second way of measuring energy expenditure with with calibrated heart rate monitors. And got the same answer. So, the Hadza we knew the Hadza data were real. Um, and then we thought, "Well, maybe it's just the Hadza." So, then we've now looked at this in uh two other populations of uh sort of foragers in South America very carefully and and looked at other data from other groups as well. But but um my lab is specifically involved in two other populations of of work. Um, we looked at this in other species and like a like a uh monkey in the zoo has the same energy expenditure as the monkey in a monkey in the wild. Uh you know, so it's it's the same everywhere and across species. So, this is a really fundamentally evolved system in humans and other species to keep your energy expenditure in in check. And that makes really good sense because you don't want to have, you know, your energy expenditure on the one hand, it's good for you cuz all that all that's all that cellular work that's doing all the stuff that you're evolved to do. You want to do that, you know, you want to have an immune system that's functioning and a and and a you know, a nervous system that's going. You want to be physically active. So, all the that cellular expenditure is good. But, if you go over, of course, right, day after day for a long time, and you if you overspend, basically, you go bankrupt. And what does that mean? Well, when you overspend calories chronically, you die. Uh so, no kidding. No wonder that the body doesn't want to do that. Now, one of the things that I found in the book that was really like, "Okay, I see how we start to weave these threads together." Is that when you look at all the genes, you said there's some more than a thousand genes that have to do with whether or not you'll end up obese. Yeah. And you said the vast majority of them have to do with the brain. Yeah. And that was like, "Woo, okay, okay. So, uh how what why does that have to do with obesity?" When we the the one of the first things that happened um after we published this Hadza data, and I think people found it really surprising. Um and, you know, uh Gary Taubes reached out to me, actually, and said, "Hey, you know, that's really interesting data." And he was super nice. I want to just be really clear. He was he was really nice and and uh collegial. And he said, "This is really interesting, and you should really think about this in terms of not calories. Don't worry about that. You should be thinking about this in terms of carbohydrate, because, you know, the reason that they're able to stay at this healthy weight isn't because of energy expenditure um or or uh calories burned. It's because, you know, of of eating this paleo diet, kind of hunter-gatherer diet that's low in carbohydrate." And I thought that's a really interesting idea. The problem is the Hadza eat tons of carbohydrates. In fact, they eat more carbohydrates than the standard American diet, and less fat. And they get it in terms of honey and tubers. Those are the ones you mentioned in the book a lot. tubers and and berries. Uh yeah. 40 to 50% of their calories come from uh from meat and fat from animals, and the rest is uh is, you know, um is plants and and honey. So, when you do the calorie you break down the calories on that, you know, you got protein and fats from the animals, of course, but then you've got about yeah, 60% of their calories even more from from carbs. Okay, so very interesting. So, we're we've got all these hypotheses that are starting that try to make sense of what's going on. They're not making sense of it. So, as you're there, you're with the Hadza, you know that okay, they're not expanding more energy. I know that obesity, the genes for that tend to be clustered in the brain, meaning that there there's a control mechanism going on in the brain that seems to have something to do with whether or not you end up getting obese. Yeah. Talk to me about the brain and the hypothalamus as the control mechanism. So, I I totally understand what you're saying in terms of why it's important to stay in that band, but how do we stay in that band? Yeah, so um So, your hypothalamus is at the center of a many tentacled system that's got its it's got its feelers out into your bloodstream, your nervous system um via your bloodstream into your hormonal endocrine system. It it also it tracks your your energy levels, basically. Uh And so, it can it can sense when nutrients come in and it can sense how much comes in. It has uh you know, it communicates with your brain stem to talk to know how much your stomach is stretching when you eat a big meal, for example. Um it can sense insulin, it can sense uh you know, protein intake, all this stuff. So, it it knows the nutrients that are coming in. It's also hooked up uh in to your reward system, basically in your brain that is the you know, the all the happy feelings you get when you eat food that's delicious. And leptin, which is a hormone that gets released when you are when your fat cells are getting packed, they they they produce leptin. So, you're able to to sense with your hypothalamus how energy's coming in. Um and your hypothalamus is also in charge of your thyroid. So, the hypothyroid the hypothalamus it communicates to the thyroid to to to turn it up or down. And thyroid hormone that gets turned What is the thyroid do? Your thyroid is like the master um the master control for your metabolic rate. So, more thyroid hormone in general makes you burn calories faster, less less thyroid hormone makes you burn calories slower. Um if anybody out there listening has had thyroid issues, you know this. Or if you're hyperthyroid, you tend to sort of you're too warm and your your body's burning calories too fast. If you're hypothyroid, low thyroid, you're burning calories too slowly. Okay, so But before you go on, sorry, before you go on because this I I am always confused by um I have my hypothalamus dipping into my bloodstream, stretch responder, like all of the things that it's checking, and I don't think it checks calories, right? [snorts] Well, what are So, how do we know what how much you're eating, right? So, there's there's two ways you know about calories. Uh you are checking nutrients in and you're checking uh your you're basically your fat stores by checking leptin levels. Uh and you're So, you don't have So, so let's unpack that a second cuz that's often that's an often a a critique. Well, there's no calorie sensor in the brain. Okay. Um Actually, there is because you you have tons of data coming into your brain about the nutrients in. And you also have uh enter information entering in your brain about when you're in negative calorie deficit. Uh so, when you're when you're burning more calories than you're eating, your brain knows both of those quite well. And one way that you can tell that the brain is able to sense calories very very precisely actually is this. Uh this is work that Rudy Leibel did in the in the '90s, but they've done it since in other studies. If you increase somebody's energy intake, you make them overeat, not crazy amounts. You can't do this forever, but about 10% more than they were at baseline, their energy expenditure will go up 10%. If you make them eat about 10% less, their energy expenditure goes to 10% less. 20% less, it can even track that. And so your hypothalamus is at a system that is matching energy intake and expenditure so precisely that you know, even in America where the typical the average American gains a couple pounds a year, that amount of weight gain is a a tiny tiny fraction of the food that's brought in, right? Um and so the you know, to to within like less than a tenth of a percent, right? You are matching it perfectly. 99.9% perfect match of energy in and energy out. And so there's no way that that's happening without some regulation about that that's sensing calories and matching it because nobody eats the perfect amount of calories every day, right? Or even every week. And so you're you're you're actually doing this level matching very well. So this idea that you can't there's no calorie measurer in the brain, I take the point that there's no, you know, in the same way that you have like a barrel response sensor to do stretch in the, you know, to do blood pressure, or you have a temperature sensor, we know the the neurons that do that. Okay. True, but we have lots of nutrient sensors, and we have lots of other indicators that tell your body very nicely about how many calories are coming in versus going out. So that's kind of a red herring, I think. So what I'm trying to get to is why we have really smart people that are like two ships passing in the night on this issue. And I have a hypothesis that literally I'm formulating in real time here, um, that part of the issue is that you've you've got the hypothalamus checking all these different things and then it's talking to the, um, the thyroid and it's dialing up or down your metabolic rate. And so you have a reaction to the things that you're intaking that will not be universal. So it will be unique to that individual and I'm sure it's a whole host of things that feed into that. So I will give you an anecdote that will explain why for me this has seemed, until reading your book, self-evident that it isn't just a calories a calories a calorie. Right. Because there is a relativistic change where I'll react one way, but my wife will react a different. So for instance, Yeah. if she if and you're going to think I'm kidding and you go to great lengths to explain in the book that people do not understand they can't track their own calories. [laughter] So but if my wife and I were to eat calorie for calorie, Yeah. the next day she will wake up and again, I'm not kidding, you can actually ring the sweat out of her side of the bed. Whereas I will just be fatter. And it is so irritating because my wife, who's like half my size, can match me by calorie and what happens is clearly her I would assume her metabolic rate is turning up, which is making her hot and so she is sweating through the sheets Yeah. in in response to the same food that does not make me sweat, but I am noticeably either retaining water or actually having put on fat, whatever the the thing is, I look fatter. Yeah. And so that that difference makes you go, "Hold on. There's something going on here other than just a calories a calories a calorie." Oh, totally. So, so the problem is that when we begin to say, "Oh, it must have been something in the food that you ate." rather than, "Oh, it's something in your individual response to that extra energy." And what I would say is, my hypothesis would be your your wife's regulation of calorie intake and expenditure it was better matched and she was able to crank up her metabolic rate and burn those extra calories off. That was her evolved response from her hypothalamic system. Yours was different. Yours did not increase your thyroid hormone in the same way and maybe it did become extra calories. Uh extra calories still on you as as weight. Um and gosh, you know, if that were true, then that would mean that the genes responsible the gene variants responsible for obesity would be where? They'd be in the brain. And that's exactly where we find them. And so, I I hear that anecdote and, you know, I think, "Yeah, that that actually mates with what what that's that matches the data that we see." The problem with the sort of carb blaming or whatever blaming that you want to do is it rather than thinking about the calories that came in and how your body responded to it, rather than thinking about, "Oh, it was one special nutrient. It was carbohydrate and it was the carbohydrate that made my insulin go up and my insulin took my the the the blood sugar and it put it into my fat cells and it didn't in her, you know, for some reason. Then the the That's a reasonable hypothesis, by the way. And I don't want to make it sound like it's we could just dismiss it. It's a really nice hypothesis. It has generated lots of good science. It just turns out not to be very true. It doesn't hold the data very well. And and here's why. If that were true, then the pathways that vary between you and your wife or that at a population level vary between people who have higher BMI and who don't, we should find those pathways and the the alleles that are the genes that are that are vary that make the difference active in those pathways and we don't. We don't see them active in the pancreas or the fat cell or the liver. We've and we've people have looked and they're not there. They're active in the brain. Secondly, um if we do controlled feeding studies, then we ought to see high carb versus high fat diets have that kind of response regardless of calorie counts. We should have people who are on high fat diets lose weight or maintain and people on high on high carb diets gain weight. And that, you know, matched calorie for calorie cuz the argument here is it's not calories, it's carbs. And when you do that controlled study, it doesn't work out that way. Um it really does come down to the the calories are what determines the weight change or maintenance, not the carb level. So, that's work that like, for example, Kevin Hall has done, but not just him. Other people have done it, too. Um and it works in the lab and it works in the real world settings where if you assign people a diet for a year and you say, "You're going to have a high carb diet and you're going to have a high fat diet." And I watch you for a year, the weight change is the same and you can lose weight on either of the diets depending on how well you stuck to the calorie counts, not the carb counts. Um and this is the most exciting one. Uh I don't know if you've been paying attention to the the work coming out with semaglutide. So, semaglutide is it's called a GLP-1 re- receptor agonist. And basically, this is a hormone that gets made uh by the by by your digestive system and it triggers the um it's a it's a signal to the pancreas to make insulin because it tell you create GLP-1 when you when you eat the stomach and the digestive system sense that food that comes in and you make this hormone GLP-1. And like you'd expect it tells the pancreas to make insulin cuz you just ate so you better get ready to to deal with the the nutrients and it tells your brain that you just ate as well. Um and so they can make a mimic for this hormone. Well, this mimic for this hormone does two things. One it is it increases your insulin levels. And it tells your brain it tells your brain that you you ate. You did you didn't really but it tells your brain that you ate. This is a perfect perfect test of the carbohydrate insulin model because if it's only insulin that matters then you should gain weight because your insulin's gone up and if it's only signaling about hunger and satiety in your brain and the hypothalamus system that matters it should make you lose weight because you told your brain you ate. And it is the most effective weight loss therapy since bariatric surgery. People lose 20% weight on semaglutide. So just because they don't have a hunger mechanism cuz the brain is being told you've eaten. They stop eating. Um and their insulin levels are by the way are higher. Um at least initially. The good news is if you lose a lot of weight which you do then your blood glucose levels go down and your insulin levels go down. So they're all you know all the good things happen anyway. It's not like your insulin levels stay high forever and and high insulin probably isn't good for anybody regardless of whether or not the CIM but it's carbohydrate insulin model is right or not. Um so it gets all those things down and it's that's good but the initial input is actually increase insulin not decrease. We start getting into complex things that I think are what muddy these waters. So for instance bodybuilders routinely inject insulin as a way to grow more muscle because insulin gives your body the signal to grow and so you start getting into nutrition partitioning and telling instructing the body what to do with the nutrients. Yeah. And if it's true that insulin tells your body to grow, which is why bodybuilders inject it, and eating a high-carbohydrate diet spikes your insulin, then it's obviously it can't grow without taking more of those nutrients to your whole point about energy. So now I've given my body a food that signals to retain this energy versus giving my body a food that either just doesn't have that signal or signals to dial up the burn rate or whatever. It it comes down to calories in a hyper-relativistic way. In that some people will respond to that excess of calories differently than somebody else. So my wife, her metabolic rate seems to go up, whereas mine doesn't go up, certainly not as effectively. It doesn't match as well to use the words you used before. Yeah. And so it creates potentially it's not even it it is an illusion in terms of it isn't that I broke the laws of physics, but it's also real that I put on fat and she doesn't. And so it's sort of of little um consolation to somebody that is like, "No, no, no, you did the laws of physics are are there." It's like, "Well, I'm getting fat and this person is not." Well, yeah, I think that's the I think the response is individualistic and I think also the the diet you know, the hedonistic response. Do I keep on plowing through this plate of food or am I done? That's also going to be very individualistic. And people who go on low carb and say, "This is amazing. I've I can eat all the calories I want and I never get Yeah, I never get big. In fact, I've lost weight." You know, that's great and I'm so happy for them. Other people say, "I went vegetarian and I eat all the carbs I want as whole vegetables and I you know, and I never count calories, I lose weight. That's great, too. And the reason it's working is that I, you know, two two sides of the coin here. One is that you're actually just stopping earlier. You feel full. You feel great. And that's the that's the holy grail, isn't it? That you have a diet where you you just feel like you ate exactly enough, and you feel really good. Um, and that can happen on a a range of diets where different people are going to find it what diets that work. And also, I mean, I think you're probably right that the response to the to overeating that the the way that the body manages that calorie excess, if you do go over, is going to vary by people as well. Um, that would be really fantastic to be able to to lock down and test and see. I'd love to see that. We haven't We don't know that yet, but I think it's it's plausible that that's that variability happens, too. In every case, we're still talking about a sort of brain-centered system rather than, you know, a pancreas adipocyte-centered system. And so, that's if people are kind of on Twitter watching the arguments between the carb folks and the energy folks, that's you know, if what I just said sounds reasonable to you, then that's not actually the argument. The argument is is this more in the weeds, is it fat cells and pancreas, or is it brain cells and sensing? So, as you look at all this data, um, how do you You're obviously in shape. How do you think about lifestyle? Like, what's the right way to go about it? What do Like, do we have the occasional Twinkie? How do you How do you approach it? I, uh, and maybe this is just the way I'm wired, I just wish we would take the, you know, turn the temperature down on this stuff a little bit. The emotional temperature. The emotional temperature on this stuff down. Uh, I one of the great gifts of my career, uh, being an anthropologist is that I am It is It's job to keep eyes open and look across cultures and look across human experience and see that diversity and understand all of it is pretty normal. Right? That the that the the universe of normal for humans is pretty darn broad. And so I get nervous and I just I'm skeptical about anybody who's trying to sell you a very narrow view of what normal should be or what healthy should be. And it has to be this and it can't have any of these. And you know, I'm not sure about that. I think try to stay as active as you can, more active the better. Uh unless you have overtraining syndrome, then you've done too much. But none of probably you're not there unless you're like an Olympic level athlete. Um so we should all be exercising more. Uh I think if we can do it outside, all the better. Um I think you know, some people are going to find diet-wise that a really strict diet works great for them because that works for the way that they're wired and they're strict cuz I know people are going to want to hear what what they should be eating a I mean a diet that has a diet that has a lot of bright-line rules. I don't eat any of this, you know, I look at my list of foods that Americans eat then I cross off you know, half or more of them and I just never ever eat them ever. Um I think the most common had to pick uh like a thing to judge them by, would it be whole food is always best and so don't eat anything processed or do you have like what are your bright-line rules or what bright-line rules could we extract from the Hadza? Like I'm not sure the But for somebody who really wants optimal health. Okay. Yeah, I think the best thing to do would be to avoid ultra-processed foods. Yeah. I think Because they're hyperpalatable or is there something else that makes them problematic? There's a few things. One is they are hyperpalatable so they they screw up that hedonic response You you overeat cuz you don't ever feel full and you always feel your brain is always excited about it. Um they are typically in the processing, they are uh any fiber is taken away. Uh they're usually low protein. So, there are your two, you you know, there's a there's more than two, but those are two good signals to your brain that you've eaten enough is that you have enough bulk and that you have protein. Um and so you take those two signals away, then you're going to over consume. You're going to over consume carbs or fats or both because that's all that's that's all that's going to be left in this thing is carbs and fats. Um they're they ultra-processed foods commonly have lots of added sugars, which are no good, lots of added oils, which are no good. So, you know, if you can avoid those pre-packaged foods that are stuffed full of that stuff and and all the good stuff, the protein and fiber's been ripped out, if you can avoid that and and try to look for whole foods and stuff that, you know, minimally processed and not destroyed in that way, uh I I think a lot, you know, I suspect that would solve a lot of problems. I know that over half of the food off half of the calories that Americans consume these days, um over half of it is ultra-processed calories. Uh the number one single source of calories in the American diet is added sugar followed closely by added oils. So, you know, uh we got to stop doing that. I think that's what I would focus on. So, you in the book, you obviously acknowledge like there's nuance here and I'm not saying that this is good, bad, or indifferent. Is that an area that you have studied, plan to study in terms of like why is oil bad? Why is sugar bad? Like if it isn't the sort of insulin sugar answer to why people get fat, why do you worry about sugar? Oh, because I think that a hyperpalatable foods, ultra-processed foods, um they screw up the energy matching signaling that your hypothalamus does. They are too delicious, so you're pushed to overeat them. They are devoid of the signaling molecules that would typically tell you that you're full. And so, you know, when when hunger and satiety have to be in perfect balance like this and you just do that, well, now you're in trouble, right? And I think that's what I think is so beautiful about like Kevin Hall's ultra-processed food overfeeding studies. I think they show that really nicely. So, people who aren't over-consuming and aren't overweight, um then I don't think you're going to have as much of a problem. Although I'm I am point I'm walking I'm I'm tiptoeing into stuff I don't know as well, so I'll be careful, but um I don't see the issue. Now, you're so there's sort of a I don't I want to make sure we're not talking past each other. I'm not arguing that uh that just pure white refined sugar is a great idea or it doesn't matter or anything like that. No, that's what I'm trying to figure out is is what is going on? Like why is refined white sugar problematic? You've looked at so much more data than I have. If you have a hypothesis around why that's So, I get the hyperpalatable part and maybe that's it. But I'm just curious if there's anything other than the overeating or no, its problem is entirely it's just going to make you overeat. And I'm asking as somebody who wants to be able to eat ice cream. Yeah. Um I eat ice cream. Um so, yeah, I I think I think it's okay. Look, sugar is a fructose molecule and a glucose molecules molecules stuck together. And when it gets in your blood, that's what it is. And it's the same as the same fructose and glucose molecules that your body's going to break down and use that way from other carbohydrates. So, um you know, table sugar and a potato and a slice of bread and a you know a jar of honey are all going to end up being the same molecules in your blood. That that's just how that's how digestion works and that's that's reality. Now, you know, if if there if you have white refined sugar without any fiber to sort of help slow down the digestion of it and to signal that you're full, then yeah, okay, by itself that's a problem. But but I think it's not because the glucose in your blood knows it came from white refined sugar. You know what I'm saying? I don't think there's any memory that oh, I came from something bad, so now I'm going to be worse than I would be if I came from a nice a good source, right? Uh so I do think it comes down to matching your energy needs with what you eat and I don't think I think villainizing particular kinds of nutrients doesn't help. I don't know if that answers your question. No, it does. It's you know, this is a such a fascinating topic to me because I start thinking about it in terms of okay, what's going on? I step back and I look at the American population and I say even from the time I was a kid, it like so my family I grew up in a morbidly obese family and I remember thinking about it as a kid like my family's fat, yo, and like other families are not. And now it's like my family's completely normal. Like it is so common and that's in like you know, I'm only 45. So it's like not in exactly you know, hundreds of years. So in that amount of time it's become like so widespread. So you start asking okay, what's going on here? Over consumption like I'm I'm perfectly happy with the idea that look, ultimately this is a caloric imbalance for that individual person and but I think that just as you've been very even-handed about that there are also secondary consequences that beg questions. But the reason that I'm I'm not yet full and look, I fully acknowledge this is largely ignorance, but I'm not fully convinced yet that there isn't something going on with carbohydrates because I think about things like, okay, if insulin is damaging cells and there are certain things that like if I eat a sugar, a white refined sugar, this would be my hypothesis on why white refined sugar for instance is worse than honey. That there's something in honey that's slowing its absorption or something so that even though once it hits my bloodstream it's the same, but if a white refined sugar doesn't have any of those things around it to slow its absorption, it gets into my bloodstream, now things like my muscles uptaking that sugar or my liver having stores that it can fill with that, if I'm not exercising, not depleting that, and I'm eating foods that are that get into my bloodstream faster, they overwhelm the the non-insulin response systems of my body, and so my muscles can't uptake it fast enough, and now there's over way too much insulin pumping through my system, that's beginning to damage my cells, then I start going, okay, well there's a logical throughline. Again, the data may show that this just isn't true, but I can see a logical throughline to how there's other things at play here than just a caloric deficit or not. Right, so the way that you would test that is is you would assign people to different diets and you would say, you're going to eat a low glycemic index diet, high fat, and you're going to eat a high glycemic index diet, high carb, and we'll and we'll check back with you in a year. And this has been done a few times and the result is consistent. People who stick to the diets, whether it's not as high glycemic index or not, if you stick to the diet, you'll lose weight and everything gets better. Your HBA1C gets better, your your blood glucose levels get better. Insulin resistance gets better. People can be you know the the the diet fits study that you probably have heard about. Um people on the high carb low fat and on the high fat low carb diets had similar percentages of people who reversed their type 2 diabetes. Um reverse is a is a tricky thing, but they didn't they no longer need the medication. They were they were able to maintain uh sugar in a in a safe way in their blood. Um weight loss was the same. Uh and so when you lose weight this is why I tend to focus on weight and first and the secondary stuff second. When you if you're overweight and you lose the weight those measures all get better. No matter what. So if you eat the Twinkie diet but lose weight, you're you're still going to be better off. Yeah, that's right. And you probably still shouldn't eat the Twinkie diet. I'm not recommending that, but you'll be better off eating the Twinkie diet and losing the weight than eating some other diet and not losing done Have they done something like that with diabetics? Like so their weight is coming down, would they be able to better manage their blood sugar even though they're eating these high sugary foods as long as they're in a caloric deficit? Okay, so if you if your body tips over into this pathological state where you're no longer responding to insulin correctly then I think that's a different situation. And people on high fat and high carb diets who are sort of pre-diabetic have equally good outcomes. That's the diet fits series response and that's the Danziger et al 2005 study that did Atkins, Ornish, Weight Watcher. They did all about five diets, I think. So there are these diet there are those. If you are already in that pathological state where your cells aren't work you know your insulin response is is pathological. Well then I I think that's a different And I'm not going to you know, I'm not a diabetic I'm not a diabetes doctor and I'm not going to tell people what to do to keep it I know that if you keep on a really low carb diet in that state, you can do better. [snorts] But, that's talking to somebody who's already has a sort of broken response. And I I hesitate to take that as particularly instructive about what happens to people who have normal response. So, to me that's super intriguing and when I see in a disease state, it responds well to this thing, my natural inclination is well, then that's probably the thing that led you to the disease state. But, the data may not be there to back up that layman's hypothesis. So, I'm perfectly open to that. Um let me ask you, what would be your fantasy test to run? If you could lock people in a room and they only ate what you gave them, like what what is the the one question where you're like, if we could answer this, we'd really know about health? Oh, I know I well, okay, about dietary health then that's easy. You do the study that um that Kevin Hall would love to do. And so, maybe somebody's listening they want to fund Kevin Hall for this. He's already set up to do it. Rather than doing, you know, month-long or two-month-long crossover studies, you would do it for a year. And you would have somebody in a, you know, basically in a hotel room uh and you would make them you would make sure that they ate exactly what you said they were going to eat and you would do biomarkers the whole time to ensure that they were on track. And it's a very simple test. Right? If if the calorie version of this is right, then it won't matter if they're in the high carb arm or the high fat arm. Their weight gain and weight loss will be entirely due to caloric you know, the number of calories they're eating. Um and if you put them on a negative calorie balance and they lose weight, everybody benefits regardless of you know, from the weight loss regardless of how they got there. The data that I'm aware of for dietary studies that already in my mind say that that's going to be the outcome, but we haven't done the lock them down yet. So, let's lock them down and do it. And so, the flip side is if I'm wrong and calories don't matter and it's all about carbohydrates, then it shouldn't then if I have a high carb diet and a low and a high high carb and a high fat diet, the high fat diet the people should be doing fantastic and losing weight even though they're matched calorie for calorie, right? And that's the prediction of of that carbohydrate based view of the world. And we've done Kevin Hall's done the short version of that. It's not short. I mean, it's still a long time to do two-month crossovers or one-month crossovers. Um, but and we've done the long version of that where like which is diet fits, which is I give you a high carb diet and you're assigned to that group randomly and I give you a high fat diet and you're assigned to that group randomly and we see what happens in in a year. Um, and so far the data support the energy view. But but yeah, I mean, if the the the the dream experiment is is the lockdown study for a year. Man, this stuff is so intriguing. I really liked your book, dude. I took so many notes. It was freakish. Uh, it was absolutely fantastic. Thank you so much for coming on the show. Where can people connect with you, get the book, all that good stuff? Uh, yeah, thanks. You can get the book anywhere you buy books. So, if you're checking out your local local bookseller, that's fantastic. Go to the independent sellers. Uh, if you can't find it there, Amazon's got it. Um, and if you want to know what I'm doing, uh, I'm on Twitter at Herman Pontzer. And if you want to know what my lab's doing, you can find us at Duke. Yeah, or podcasts and and shows and and whatever else we we get invited to to come on and talk science to, I guess. But, uh, you know, come and find us at Duke or find us on on Twitter, that's the easiest thing.