287: Daniel Lieberman: Evolution and the Human Diet

28:45Those are the, like Lucy, the most famous of them, but there are many species of these creatures. And their things go really out of crazy, right? Their teeth are enormous. Some of them have teeth that are three times the size of yours and mine. Really thick. They have giant chewing muscles and we have really robust faces. These are chewing machines, right? They are specialized for eating very mechanically demanding foods. Hey, Chicago. Class it up with Crocs. You know back to school is coming in fast. So why wait to find your new fave footwear? Step into a local croc store and step into your new look.

29:23Try it. Style it. Make it yours. Because the right pair doesn't just show up. It shows off. First day fits handled. Walk out ready for whatever's next. Visit your nearest croc store today. When you need to build up your team to handle the growing chaos at work, use Indeed Sponsored Jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications and more. Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a$75 sponsored job credit at Indeed.com slash podcast. That's Indeed.com slash podcast.

30:04Terms and conditions apply. Need a hiring hero? This is a job for Indeed Sponsored Jobs.

30:12And what does this suggest that they had to eat? They were in very hard times or their diets just naturally? Well, they're not in forests anymore. They're in much more open habitats. And what are you going to eat in that more open habitat? Well, we know what they're eating. They're eating tubers. They're digging. They're digging underground. So a lot of plants hide their energy stores underground. That's basically what roots and tubers are, right? And I've gone out and gone digging for tubers with hunter-gatherers. And they're still out there, these foods. And they're really fibrous and they're really tough.

30:48I can tell you I've chewed them myself. In fact, you have to mostly spit them out because you can't swallow that much fiber, right? And so we have a variety of evidence, biomechanical, isotopic, et cetera, that these animals, I'm sure they would have eaten fruit when they had access to it. But they were probably digging and eating a lot of underground storage organs, which are very mechanically demanding. And they were probably having to put really high forces on their faces and therefore withstand those high forces. So, again, the story that matters for us, for you and I, because why should we care about this, is that it's not that we stopped eating fruit in our evolutionary history.

31:25It's that the history, the evolution of our diet has been accretionary. We just kept adding more and more foods. So the astralopiths are basically adding more underground storage organs to our diet. And we still eat them, right? You and I eat potatoes and, I don't know, ginger and things like that. And if you were to go out and spend a few days with Hadza hunter-gatherers in Tanzania, you could see that a very large percentage of their diet consists of these underground storage organs. And these underground storage organs that they were eating, these wild pre-cultivated ones, my guess is that just like the wild fruit that chimpanzees are eating is more like a carrot than our fruit, that these tubers would be very different from a russet potato.

32:13Oh, yeah. I've eaten a lot of them. I mean, every time I drive the people crazy when I do, you know, been out there, but I've tried every tuber they take up. They think, who is this crazy guy. And yes, no, they're extremely fibrous. And some of them, sometimes they cook them, they throw them on a fire, but they're tough and fibrous and they're not sweet. They're not like a potato. Potatoes have been domesticated to make them easy to eat. But even then, but they're actually kind of tasty. I like them. They're kind of peppery, some of them. they're quite pleasant to eat actually but they're hard to find.

32:55You have to dig them you can't just walk around and pluck them off a bush you make skill and knowledge and effort to get them and we don't need to this doesn't need to be specifically about the australopithecines but the animals or ancestors teeth changed as their diets changed. How did their internal digestive systems change in response to these differing diets i mean well we can only guess at that obviously right but if you're going to eat a lot of fiber you need a really large colon and chimpanzees already have pretty large colons so so they probably my guess is that their their digestive systems were more or less like a chimpanzee and i think the the real shift starts with the genus homo when we start eating more meat and we start cooking and that's when um i you know in our we lose our snouts or oral cavities get smaller, our teeth get smaller.

33:49And if you looked in the mouth of a homo erectus, which evolves around 1.9 million years ago or so, if you were a dentist, you'd think, well, his teeth are maybe just a wee bit large, but they basically look like yours and mine. They no longer have a projecting snout. And if you're going to eat meat, which we know they started eating, it's useful to have a larger stomach, maybe a more acidic stomach, so you can decontaminate the meat. And once you start cooking, your digestive system shifts. And so the long intestine gets smaller, the colon gets smaller, and the small intestine gets larger. And we know that from comparisons of humans and chimpanzees.

34:37And it seems reasonable to guess that that's what happened in the genus Homo exactly when, to anybody's guess. But by the time you get to us, I mean, we are, our digestive systems are sufficiently different from a chimpanzee that, you know, we can't survive on, on raw food unless that raw food is really high quality. That's why raw foodists have such a hard time getting enough nutrients, even, even if they're shopping at, you know, Whole Foods or, or wherever, right, getting really high quality foods, they're, they're still struggling to get, get enough nutrients. And, you know, many, many female raw foodists don't get enough energy to support their normal ovarian function, so they don't have normal menstrual cycles.

35:16A lot of them lose weight. It's a real struggle. And as somebody who's tried a raw food diet, I can tell you it's really hard. You spend a lot of time eating an enormous quantity. It's really challenging. Right. Of course, one of the interesting progressions throughout FedUp is that you tried many of the diets that you document in the book for two weeks period two week periods and it seemed like the the raw food diet was one of the more trying diets for you that's an understatement I mean it was really awful I couldn't stand it I mean my wife years if I recall yeah my wife my wife got depressed I mean after three days she just um I think this is in the book but I remember she like one day she disappeared and and came back looking really happy.

36:01And she went out to a local store and got a bagel and, and that was that for her. Um, I managed to, to stick it out another day, but you know, it was, it was hard. I mean, I was constantly hungry. Um, I didn't put this in the book, but I was pooping just a lot, um, because you're eating so much food, right. And I still was hungry all the time. Uh, I'm a runner and I didn't like that. Um, uh, yeah, it was, and I just kind of, and the amount of effort just to kind of, you know, cooking is a very efficient way to process your food if you're constantly pureeing and chopping and dicing. And it was just a lot of work.

36:36It was very frustrating. Something counterintuitive, I found counterintuitive, you said when describing changes in the digestive system, is that our stomachs would get larger when we're eating meat. I would just assume it would get smaller, notwithstanding the need for acid to decontaminate, but just because when you're eating such less dense food. Yeah, I'm not sure about the stomach size. The key change in our stomachs is that they're more acidic. Okay. Yeah, that's it. We have more acidic stomachs than, say, chimpanzees. And that's a likely adaptation for digesting meat. I don't know about size.

37:18Okay. And Homo erectus, you said we're upright as it is contained in the name. Is that also when we start to become more intelligent, become runners, maybe become... That's when we become hunter-gatherers. So, you know, there's a transition from Australopithecus to Homo erectus. You know, there's these species in between, Homo habilis, Homo rudolfensis. We're still trying to figure that out. So the exact transition from Australopithecus to Homo is still a little bit murky. But by the time you get to Homo erectus, you have creatures that are very much like us. I mean, they're not exactly like us, but from the neck down, they're quite like us.

38:03And they begin to have larger brains. They no longer have snouts. They have vertical faces.

38:12They're clearly hunting and gathering. They're dispersing over the world, so they're not just in Africa. We find them in the Caucasus and in Europe and in Asia. They're cooperating. This is really, for me, the big shift in human evolution. And, of course, if you met a Homo erectus, they're not exactly the same as a Homo sapiens, but this is a critical shift that gets us to where we are today. We would not be who we are had it not been for Homo erectus. I'm actually going to be speaking with Richard Wrangham in a few weeks. Great. His office is just over there. Maybe it would make more sense to speak with him about the development of human intelligence and its connection to meat eating and cooking.

39:06if you would prefer right now to focus more on contemporary humans and our diet. I mean, I'm interested in that topic, too. I mean, the thing about Homo erectus is that, you know, for me, what the species is about is about getting more energy, right? And that's what life is about. It's about getting energy to produce copies of yourself, right, to reproduce. And what the hunting and gathering system did is that hunting and gathering gave humans more energy. It did so through a combination of the fact that we started eating meat. Meat is a very nutritious food. It also came through food processing.

39:44So you have stone tools, which not only, you know, which you can mechanically process food. We published a paper in Nature a bunch of years ago, Zink and Lieberman, where we showed that just using simple stone tools increases the amount of energy you get from food because you can break food into smaller particles. So fascinating. You can digest more easily. So you don't have to have cooking in order to get more energy from your food. Just some tools become very important. You have cooperation. You have food sharing. You have this kind of network of behaviors that all together give you more energy, right?

40:16And more energy means that you can now relax selection on all kinds of things, including brain size. So just having more energy doesn't make your brain get bigger, right? But brains are expensive. Our brain, right, you and I now just sitting here, it takes up about 20 % of our metabolism. So like one out of every five of your breaths is now paying right now just for your brain, right? So brains are expensive. They're easily damaged. They're high maintenance. I mean, you need a lot of energy for your brain. And so having extra energy releases selection, releases the constraint, excuse me, on selection in order to have a larger brain.

40:56And then in turn, having a larger brain makes you probably a better hunter-gatherer, right? It just enables you to be smarter. It enables you to be a better hunter, a better gatherer, a better cooperator, a better communicator. And all of this leads to a kind of a positive feedback loop. And so that's something I've published on. But you can see within the genus Homo erectus, the earliest species, earliest individuals in that species have brain sizes about 800 cubic centimeters, right? By the end, they have brains that are almost the size of a human being. So there's, within the species over time, you graph time on the x-axis, brain size within Homo erectus on the y-axis, you just see this increase, right?

41:33And that's evidence for more energy, releasing selection to allow brain sizes to increase, which of course is in some ways relevant to intelligence and cooperation and all the other things that make us very special. where after homo erectus do the changes occur that might lead toward like the paleo diet or what people believe the paleo diet should be i mean god only knows what the hell the paleo diet is it's it's based on a from my understanding it was based on there's a thing called the ethnographic axe atlas by a guy named murdoch and i think what they did is they kind of looked at the ethnographic atlas, did some statistical manipulations with the diet, with the data there.

42:23Most of the data aren't really very good, and then came up with some kind of percentages of what they thought a true paleo diet was. We actually published a paper in the American Journal of Clinical Nutrition a few years ago, where we analyzed all the really high-quality diets of hunter-gatherers from the tropics and compared them to the paleo diet. Turns out, none of them are like the paleo diet. In fact, there's incredible diversity among tropical hunter-gatherers in terms of what they... But the paleo diet is meant to be some sort of or a home hunter-gatherer that we evolved from. Although a lot of the data come from Arctic or temperate hunter-gatherers.

43:05And of course, most of us, humans, homo sapiens evolved in Africa. So it depends on where you want to start the clock, right? But it's some kind of inchoate hunter-gatherer diet. But the thing is that when you study hunter-gatherer diets, contemporary and or even look at archaeological evidence, there was no one hunter-gatherer diet. They're incredibly varied. We evolved to eat everything, right? Remember, because we didn't evolve to eat for the sake of our health. The thing that natural selection cares about is reproductive success. So we evolved to eat whatever we could in whatever fashion we could in order to have as many babies as possible.

43:46And so for me, the biggest problem with the paleo diet is this naturalistic fallacy that somehow if our ancestors ate it, we're adapted to eating it, it must be healthy for us. That's just not the right way to think about it. The other problem, of course, is that there is no one paleo diet. They're incredibly varied. There are hunter-gatherers who eat 90 % of their diet is meat, and there are hunter-gatherers in which 90 % of their diet is plants, and there's everything in between. And then last but not least, the paleo diet claims that our ancestors didn't eat legumes, so no beans, no peanuts, no lentils, no chickpeas, whatever.

44:23It also claims that our ancestors never ate grains, and they claim that we're not adapted to these foods. And that's just not true. If you look in ethnographic data, for example, I can just see on my bookshelf over there, there's this famous ethnographic study of the Kalahari San, the hunter-gatherers from the Kalahari. The second most commonly eaten food in the Kalahari is something called the marama bean, which is a legume. So don't tell me they don't eat legumes. And we have archaeological sites from various parts of the world where we have evidence in halves of the remains of grains and other sorts of things.

44:57So the paleo diet's sort of elimination of certain foods is based on, well, they just get it wrong. Finishing the evolutionary story, though, when did Homo sapiens, when do the first individuals that we classify as Homo sapiens arrive in the fossil record? and how different, if at all, is the contemporary digestive system to those earliest Homo sapiens? So a bit of a debate still, but there are some fossils that are dated to about 300 ,000 years ago that some people have claimed are the earliest Homo sapiens and they're Homo sapiens-ish. But somewhere between three and 200 ,000 years ago is when Homo sapiens evolved.

45:49and, you know, do we know exactly what their digestive systems are like? Of course not. But are they much like ours? Probably. But, you know, the thing about our digestive systems is that we have a very generalized digestive system. It's not, you know, we talked earlier about the differences between us and a chimpanzee, but they're pretty, they're not that huge, right? I mean, we have a smaller colon and a larger small intestine and a more acidic stomach and a slightly smaller oral cavity. But overall, we just have very generalized digestive systems. What makes our ability to eat everything extraordinary is not so much our digestive system.

46:29It's food processing. It's cooking. The fact that we can cook foods is what really enabled humans to eat pretty much everything under the sun. Just take grains and legumes, which we just talked about. In their wild form, you can't eat them, right? I mean, in their uncooked form, excuse me. So if you have uncooked beans, you can get quite a real mighty stomachache, right? Because they have these things called lectins and phytates and whatever. But if you cook them, you pretty much denature those proteins that inhibit absorption of nutrients. In fact, in some cases, you completely eliminate those.

47:01And so they're absolutely fine to eat. Same thing with grains. You don't want to eat raw wheat. I would also give you a mighty stomachache. But when you cook them, they're just fine. So it's really cooking. It's the extra oral, extra digestive effects of cooking that really made us the ultimate omnivores in the animal world. It's not our digestive systems. And I think, and you can tell me if this is the wrong way of looking at it, but that this makes us unique among animals. Not the fact that we cook, but the fact that if we were to look at an ungulate, say a cow, we could look at its digestive system and say, oh, these five stomachs are very well suited to digesting grass.

47:49But if you look at the human digestive system, perhaps it is less instructive about what we should eat because cooking has enabled us to eat anything. Yeah. Yeah, it's basically it. We have a very generalized digestive system, and it's cooking and food processing. Fermenting is another one that have enabled us to become the ultimate omnivores. It's also our ability to inhabit many different habitats. I mean, most species are adapted to a pretty restricted range of habitats. But humans, because of hunting and gathering, have dispersed all over the planet. Africa itself is incredibly diverse in terms of its habitats.

48:30But then you add all the other habitats in Eurasia and now the Americas, of course, and the Oceania. It's incredible, right? But humans, wherever we spread, we were able to figure out foods to eat in those environments and figure out how to process them and turn them into babies. And so it's the combination of cooking, processing, and our culture and cognition and cooperation, all of these things together, made us able to eat a greater range of food than I think any other creature can eat. Even rats, which can eat a fair amount. I think humans can eat a much more diverse diet than even rats. Of course, they eat a lot of our food.

49:17Are there any foods that you think explaining what cooking does to them would best illustrate how transformative cooking has been for humans? For instance, like foods that could not be eaten before we could cook them. Well, I mean, beans are a perfect example, right? We just talked about them before. Beans in their raw form have enough compounds in them that prevent you from digesting them. But when you cook them, you neutralize and reduce them to completely harmless levels, making beans extremely healthy foods. And, you know, legumes are full of protein and all kinds of other compounds, antioxidants, etc.

50:04I mean, there's a reason people think that beans are healthy. because they are. They're really loaded with nutrition. And you combine, and think about what farming diets are based on. I mean, the classic farming diets, rice and beans, corn and beans, bread and lentils or chickpeas, soy and rice, all the classic farming diets are based on mixing a cereal or grain with a legume. The combination of those two gives you a complete range of amino acids. You have all the protein you need. and then you add various other, you add some nuts and fruits, et cetera, and some dairy. You have a very nutritiously diverse diet.

50:47So yeah, beans are a perfectly good example, but cereals are another example of foods that we really need to cook. And you mentioned, I think in your response to my first question, even maybe, you mentioned this metaphor of the hedgehog. And I know that there's also a fox. And it seems like this might be a good time to introduce that extended metaphor and what it expresses about how humans you think should eat today or think about eating. I think it's how we should think about eating. So there's a famous little fragment of parchment from, I think it's the 7th century BC by a poet named Archilogos of Paris.

51:28And he wrote various kinds of poems, but this little fragment says, the fox knows many things, but the hedgehog knows one big thing. That's it. That's what's on the fragment. And that fragment of that little bit of poetry was expounded on in a wonderful essay by the philosopher Isaiah Berlin, who wrote an essay called The Fox and the Hedgehog, which is actually about Tolstoy. That's when I first read it, because I'm a bit of a Tolstoy fan. and um and and and the argument is that you know when you chase a fox it'll do anything to run away right it'll it'll it'll either run super fast or it'll hide or you know it'll it'll try to try to fool you in terms of where it's going but if you chase a hedgehog it does only one thing it rolls into a ball right so that's that that's the idea behind you know the fox knows many things and hedgehogs knows one big thing.

52:24And Berlin expanded that to say that there are different kinds of thinkers in the world. Hedgehogs are people who have just one big idea, right? You should only eat foods with lots of protein, or you should never eat plants, or you should only eat plants, or whatever. Whereas foxes see complexity. They see nuance. They see trade-offs. They see that the world is complicated. And I firmly believe that, and looking at all the different diets out there, a lot of them are basically what I call hedgehog diets. They're big idea diets. The raw foodist idea was based on this idea that if you cook your food, you lose nutrients.

53:03The paleo diet, if you eat what our ancestors eat, you'll be healthy. The low carb diet, if you never have carbs, you keep your insulin levels low, you'll never gain any weight and you'll lose weight. If low fat diet, fat is very full of energy and bad for your heart. Therefore, eliminate saturated fat. Most of the big diets out there are what I would call hedgehog diets. And so I set out to try to think about diets from a more evolutionary perspective and a more Fox-like perspective and think about their trade-offs and the complexities and the nuances. And I think that we would be much better off in our society, not only when we think about diet, but lots of other problems is trying to think that we have these magic bullet solutions that give us quick fixes because they're really the case.

53:51And diet is no exception. Hey, Chicago, class it up with Crocs. You know back to school is coming in fast. So why wait to find your new fave footwear? Step into a local Crocs store and step into your new look. Try it. Style it. Make it yours. Because the right pair doesn't just show up. It shows off. First day fits handled. Walk out ready for whatever's next. Visit your nearest croc store today. When you need to build up your team to handle the growing chaos at work, use Indeed Sponsored Jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications and more.

54:34Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a$75 sponsored job credit at indeed.com slash podcast. That's indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. Now, before we move on in a certain sense from evolution, I just like to kind of sum up what I've taken away from this point up to this point, which is that evolution explains to us why our diet, why our why our digestive system is the way it is. But because of the advent of cooking, it is less instructive about what we should eat than what other than it might be for other animals.

55:25However, because we understand or know that humans evolved to eat a wide variety of diets, we should be skeptical of these big idea diets that are kind of very artificially stringent and be paying more attention to these sorts of varied diets that are eaten by, I don't know if you want to call them hunter-gatherer populations. Well, I think it's a bit more complicated than that. I mean, evolution also gives us some theory to think about, for example, aging and how to think about aging and health and think about trade-offs and think about issues of optimization. So evolution isn't just a story.

56:07It's also a series of – it has a variety of insights that help us evaluate trade-offs and constraints and just sort of think differently. So it's a bit more than just that story. The reason evolution matters is that evolution explains why things are the way they are. And there are a lot of whys when it comes to diet. Why is it that we eat what we eat? But also, why is it that as we age, our metabolisms change? And why is it that we shut off reproduction at a certain time? And I could go on, right? There's lots of why questions. So evolution helps us answer those why questions. But evolution on its own is not sufficient.

56:55Evolution is just a tool that we should combine with other forms of information, like biomedical information. I mean, one of the problems with diet, right? So look, for most of human existence, until very recently, people ate for one reason only, which is to get to the next day, right? Feed their family. But now we're in this very unusual time period where the average life expectancy in the United States is 79. And so we're living past our reproductive age. We are no longer foraging and hunting for our grandchildren. And now we're interested in what we can eat so that we can avoid heart disease and diabetes and all kinds of other foods that make us sick now.

57:37and why is it that a surfeit of sugar, why is it that lack of fiber, why is it that those foods make us sick? But also, it's very hard to figure that out just from an evolutionary perspective, because the mismatch idea only takes you so far. You also need to integrate that with biomedical evidence. When I eat something or eat a particular diet, it can take decades, many decades sometimes for those effects to manifest themselves in my health. So evolution alone is not sufficient to help us answer these questions. It's just an important

58:21component of the way we should think about diet. And so then when you, well, maybe I should ask next, what are the diets that you felt were most important in this research arc for you of writing this book for thinking about human diets and what we should eat? I don't think I think there's any one that's most important. I mean, the first part of the book, I tell the history of diets, right? From that last common ancestor up to the industrial revolution. And each of those diets, right? Each of those transformations, cooking and the development of agriculture and the spread of humans around the world and the diversity of foods and the ability of fermentation.

59:04Farming could not have succeeded without fermentation. All of these are important components of the diets that we eat today. And then the second half of the book is about diets in the modern industrial world, because you and I aren't hunter-gatherers. You and I, when we go to the supermarket, there are something like 40 ,000 foods in front of us in a typical American supermarket. We no longer have to get our food or know much to get our food. We now have to know something about how to choose our food. And so the second half of the book is about all the various kinds of major industrial era diets to help us evaluate all the trade-offs and complexities, again, from a Fox-like perspective, not only in terms of nutrition and digestion, but also their effects on things like cancer and heart disease and diabetes and Alzheimer's.

59:58There's a lot of information. But it's, so there's, yeah, there's no one diet I think that's most important. Sure. Maybe I should rephrase the question and say, I mean, certain diets like a carnivore diet or a fruitarian or raw food diet don't seem to maximize all the outcomes the way a fox-like diet would. These are hedgehog diets. I'm wondering which, if any, diets that are more fox-like do you find strike all of the, or check all of the boxes for perhaps maximizing longevity, enabling you to go on the runs you want, enjoying the food you like? Well, look, first caveat, there's no such thing as an optimal diet or diet that maximizes anything, All diets have trade-offs.

1:00:50But if you look at the evidence, right, at the diets that consistently, in terms of health outcomes, right? So we're talking about cancer, heart disease, Alzheimer's, diabetes, things like that, right? Or proxies like inflammation, levels of inflammation, cholesterol levels, things like that that predict outcomes. The ones that consistently come out on top with the most evidence to support them are diets like the Mediterranean diet. In fact, probably the Mediterranean diet would be the diet because it's been studied the most, right? But there are, I don't know, I can't even count the number of high-quality studies that have now been done on the Mediterranean diet, which show that people who eat this kind of diet, and we can talk about later on what the Mediterranean actually means, But depending on how you define it, but there's the diet that people in the Mediterranean diet eat and the diet that the people who study these diets call the Mediterranean diet, capital D.

1:01:50But those diets are associated with lower levels of obesity, much reduced risk of becoming obese. They're associated with much lower levels of heart disease. They're associated with much levels of cancer, with much lower levels of other diseases-related inflammation. but that's probably partly and and and the and the thing about those the mediterranean diet is it's kind of like as i point out in the book it's kind of like taking the best of various other diets and combining them right if you think about a low calorie diet versus a low fat diet which is usually a low saturated fat diet versus a low carb diet well the mediterranean diet is actually kind of a low all of those it's all the above um and um but i would probably say that um that a traditional Asian diet's probably not too different.

1:02:36There's just not as much research. Traditional Mesoamerican diet, I will make a bet, would have similar health outcomes. Again, there just hasn't been the intensity of research because of where researchers are. So yeah, so I would say these traditional farming diets that are based on unrefined cereals, so whole grain cereals instead of refined cereals, not too much saturated fat, Lots of plants, legumes, nuts, seeds, monosaturated fats like olive oil, polyunsaturated fats. These are the diets that consistently come out on top in terms of health outcome. Now, if we put a plate filled with bountiful Mediterranean diet food, a plate filled with like Twinkies and junk food before a cow.

1:03:32I think they would, I could be wrong, but my guess is that they would probably just keep eating the grass that's right in front of them. If you put a heaping pile of Mediterranean food in front of like the average American and then a Happy Meal from McDonald's in front of that same American, my guess again is just that they will go for the McDonald's. What is it about our digestive system? And maybe it's a cultural thing or how it's not our digestive, it's our brains. It's not our digestive systems. So it's our brains. Look, these foods have been engineered, right? You're talking now about ultra processed junk foods, basically now, um, rather than, so these foods have been deliberately engineered to appeal to us, right?

1:04:22In the book, I describe like a McDonald's Big Mac, right? Think about what the Big Mac has. It has savory, it has sweet, it has salty, it has bitter, it has cold, it has hot, it has different textures. I mean, it's a food that has been cleverly and carefully designed over the decades to appeal to our sensations, right? And to make us want to eat them. The same thing for Doritos. There are something like 30 different flavors in a Dorito, none of them too high, so that you get this balance of flavors that keep you reaching for more. M &Ms. When you have a bowl of M &Ms, the reason there are so many colors is that when you have different colors, your brain wants to pick out, and I'll try the red one, I'll try the blue one, I'll try the green one, I'll try the brown one.

1:05:12These foods have been engineered to be hyper palatable to appeal to us so that we eat a lot. And in fact, the experiment that you just discussed has actually been done. It's called a cafeteria diet, right? There are people who have done experiments where they put people in front of these foods and to find out how much they eat. And they eat an awful lot because surprise, surprise, these foods are carefully designed. And the reason they're carefully, the reason they work so well is that there's actually a wonderful book. I highly recommend it called Salt, Sugar, Fat by a guy named Michael Moss.

1:05:44He was a New York Times journalist, won the Pulitzer Prize, where he investigated how food companies designed these foods. And one of the tricks, and there are many tricks, but one of the tricks is to hit what the company's called the bliss point. So if you have a food with a lot of fat, it's kind of greasy and overwhelming, right? You don't really want to eat it. Or the same thing of a food that's got too much sugar. It's cloying and it's overly sweet. Or food that's too salty. But guess what? You have a lot of fat plus a lot of sugar plus a lot of fat salt. These things kind of all balance each other out and they light up our brains because we get really excited.

1:06:21Our brains get really excited by foods that are high in both sugar and fat, probably for evolutionary reasons. You know, the only food, can you name a food that's natural, right? It doesn't come from a factory that's high in both sugar and fat. Oh, milk. Exactly. Your mother's milk. Milk is full of sugars. and it's full of fat. But in nature, you don't find foods like that. But we love them, right? Think about ice cream. I could go on, right? And these are the foods that are also the most fattening, but they're also very appealing. So these foods have been designed to make us eat large quantities.

1:07:01hmm your book fed up it is not a weight loss manual uh by any means but how does your research point you toward dealing with this problem of this mismatch between our brains and our food environments well i mean i have i have two chapters on obesity and and i do discuss weight loss to a great extent. But I mean, the thing about, well, there's two issues to weight. Well, there's many issues to weight. It's a very complicated topic. But one of them is that weight loss and weight prevention are different things, right? So one issue is what kinds of diets help prevent us from gaining weight. And then the second issue is if we are trying to lose weight, which a lot of people are today, 42 % of Americans are classified now as having obesity.

1:07:53And another 30-something percent are classified as overweight. So over 75 % of Americans are either overweight or obese. And in a given year, about half of them are trying to lose weight. So it's a very major issue. And GLP-1s, which are really fascinating, are changing the game for a lot of folks. And the reason GLP-1s are changing the game for folks is that the hardest part about losing weight is hunger. We evolved to have extra fat, and I discuss in the book. And perhaps you remember that section where we talk about why and how humans evolved from being, you know, chimpanzees have maybe about 5 % body fat.

1:08:32Humans evolved to have at least three times as much body fat, even lean humans. And we evolved to put that fat on for all kinds of evolutionary reasons. But we never evolved to lose that fat, right? Because that fat was such an important evolutionary adaptation. and because obesity was so rare, there was no selective benefit for learning how to lose fat, for being able to lose fat during our evolutionary history. So we evolved to pack on fat. We never evolved the adaptations to lose fat. And what happens is that when we lose weight, when we diet, we go into what's called negative energy balance and we're taking in fewer calories than we're using, our bodies turn on all these adaptations that make us hungry.

1:09:14And then it's very hard to overcome hunger and appetite. You have hormones like ghrelin, which your stomach produces. You have leptin, which is produced by your fat cells. You have PYY and CKK, and they're produced by your intestines. I mean, GLP-1, et cetera. All these hormones that are being produced that make us want to restore our body weight back to that previous level. And so if you're going to lose weight, you have to overcome that hunger. And so I do discuss in the book those adaptations and how and various ways in which people have tried to overcome it. But that's the challenge. And that's why GLP-1s work so well for many people is because they turn off that hunger.

1:10:13Try it. Style it. Make it yours. Because the right pair doesn't just show up, it shows off. First day fits, handled. Walk out ready for whatever's next. Visit your nearest Crock store today. When you need to build up your team to handle the growing chaos at work, use Indeed Sponsored Jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications, and more. Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a$75 sponsored job credit at Indeed.com slash podcast.

1:10:52That's Indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. And as you pointed out and fed up, there isn't good long term data, obviously, about GLP ones yet. But do you have a position on whether, given the limited data we do have, you think there's something that people who struggle with obesity should strongly be considering? Well, I'm not a physician, and I wouldn't dare to tell people what they should do. But look, GLP-1 has been incredibly helpful. I have friends who've taken GLP-1s. It's really helped them a lot. But we need to be thoughtful about who takes them and for what reason.

1:11:42And one issue is that when you go off GLP-1s, and a lot of people go off them for one reason or another, for many people it's cost, especially if your insurance company decides not to pay for it anymore, which has happened here in Massachusetts, then your appetite comes roaring back once you stop taking the GLP-1s. So you have to be prepared for that and think about what you're going to do. Another issue is that people on GLP-1s tend to lose a lot of muscle. And that makes you at risk of old age, of losing muscle mass, especially as you age. So it's really important to do strength training and eat enough protein if you're taking GLP-1s.

1:12:17But they seem to have all kinds of benefits. So I think it's really interesting. I mean, we're doing an experiment in real time. I wouldn't tell people not to take GLP-1s, but I think they just need to be thoughtful and sensible and work with a physician so you take them very well. But the other thing is that the GLP ones are incredibly helpful for people, but they don't prevent people from getting obese in the first place. And I'm also concerned about prevention, right? How can we... There's something like 20 % to 30 % of American teenagers, adolescents, are classified as having obesity. That's a staggering figure if you think about it, right?

1:12:53Those folks are going to be struggling for the rest of their lives with their weight. And the reason they're doing so, a large part of that, there are many factors that cause obesity, but one of them is the nature of the food that's out there. Again, you walk into the supermarket, there are 40 ,000 products, and somewhere between 50 % and 70 % of them are unhealthy, ultra-processed foods that promote obesity. So we need to have, we need to, I'm worried that GLP-1s, which are really great for some people, that it's going to take our eye off the problem of how to fix our food system so people don't need to take them in the first place.

1:13:32That's really my concern as an evolutionary biologist. Well, this is the last thing that I'll ask for today because our listeners can go read Fed Up if they want the full story. But how would you, in a nutshell, advise somebody to eat more like a fox with perhaps explicit principles or pointers? Well, again, going back to what I said before, our ancestors needed to know a lot to get their food. To be a hunter-gatherer, you'd have to know, you have to be a naturalist. You have to know about animals and plants and how to process food. And it's just not easy to be a hunter-gatherer. If you're a farmer, you need to know a lot how to grow your food, right?

1:14:14You need to know about the seasons and behavior of plants and processing. and is, you know, farming is also very challenging. It requires an enormous amount of knowledge. Now we just walk into a building and like there's this infinite amount of food or we can get online and we just order, you know, DoorDash and it just brings us whatever we want. Dial a number and pizza is delivered to your door, right? We don't need to know anything anymore about how to get our food. But the fact of the matter is that we now need, because we have this incredible abundance, this cornucopia of foods, many of which don't do us any favors, we now need to know something about how to choose our food.

1:14:52And that means knowledge, right? And what I tried to put into the book was the knowledge I think that everybody should have about saturated fats, about seed oils, about inflammation, about carbohydrates. And we haven't talked about the carbohydrate insulin model at all today. And I mean, and it's not all that abstruse. It's not actually all that difficult. It's not any more complicated than most of the topics that we learn in high school about geometry or American history. It's just that we don't teach it. In fact, we don't even teach this stuff to doctors. A lot of what's in this book is not taught to most physicians.

1:15:32It's not that hard. It's not that abstruse, but it is knowledge that we all need. The reason I wrote Fed Up was to try to give people the information that I think any eater today in the modern food world needs to know. We just need to educate ourselves and make our own decisions because what's the best diet for you is not necessarily the best diet for me. Some of us, you know, we just look at a cracker and our cholesterol levels go up and some of us, you know, some of us can eat as much saturated fat as we want. It has no effects on our LDL levels and it's complicated, right? So we just need to know something about food and diet and digestion and nutrition to make our own decisions and do so not by following some person on TikTok who comes up with some elimination diet or some doctor who's trying to make money by peddling a particular hedgehog diet.

1:16:22We need to be foxes and understand their complexities and nuance. But it's not that hard, and it's actually kind of fun, and the information is sort of interesting. So I hope that the book is empowering and fun. I filled it with stories. There are all these interesting people who have figured all this stuff out. There's all anecdotes. It's fascinating stuff. And also, I think, useful and just helps us all live healthier, better, more enriching lives. Okay, awesome. Well, Dan, thank you so much for having this conversation with me today. I've really enjoyed it. My pleasure. Thanks for asking me.

1:17:07The right window treatments change everything. your sleep, your privacy, the way every room looks and feels. At Blinds.com, we've spent 30 years making it surprisingly simple to get exactly what your home needs. We've covered over 25 million windows and have 50 ,000 five-star reviews to prove we deliver. Whether you're DIY it or want a pro to handle everything from measure to install, we have you covered. Real design professionals, free samples, zero pressure. Save up to 40 % when you buy two or more. Rules and restrictions apply. Close your eyes, exhale, feel your body relax, and let go of whatever you're carrying today.

1:17:44Well, I'm letting go of the worry that I wouldn't get my new contacts in time for this class. I got them delivered free from 1-800-CONTACTS. Oh my gosh, they're so fast. And breathe. Oh, sorry. I almost couldn't breathe when I saw the discount they gave me on my first order. Oh, sorry. Namaste. Visit 1-800-CONTACTS.COM today to save on your first order. 1-800-CONTACTS