Exercised: Why Something We Never Evolved To Do Is Healthy and Rewarding | Talks at Google

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[MUSIC PLAYING] PETE WILLIAMSON: Hi. My name is Pete, and I'm your host today. Dr. Dan Lieberman is a professor of human and evolutionary biology at Harvard University and a pioneering researcher on the evolution of human physical activity. He's here to discuss his book Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding. People watching the talk will see a YouTube chat window over to the right. If you type your questions into the chat, we'll have time for a short Q&A after the main presentation. And we'll get to as many questions as we have time for. So this is what the book looks like. And please welcome Dr. Dan Lieberman. DAN LIEBERMAN: Thanks for having me. So shall I get started? PETE WILLIAMSON: You're very welcome, yeah. Please go right ahead. DAN LIEBERMAN: All right. Well, I'm going to share my screen and use some slides to talk my way through this. So it's a real pleasure to be here and to talk about this book I just published. It came out last week, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding. And I thought I'd start by imagining that this audience is representative of the US public in general. And if that's the case, about 20% of you probably got 150 minutes of physical activity a week, which is the recommended minimal dose by every major health organization in the world-- the American Heart Association, the American College of Sports Medicine, the US Surgeon General, et cetera, et cetera, et cetera. But the other 80% of us didn't get 150 minutes a week. And that's just 21 minutes a day, right? And those of us who do didn't are often confused about it, and ambivalent, and anxious, and feel shamed and nagged, and fed up with the whole talk. And so if you're one of those, you, probably the last thing you want to do is to see a book about exercise and somebody promising you 70 easy steps to get ripped to run a marathon, or whatever, all that kind of stuff. But I can assure you that is not my goal today. What my goal today, really, is to do is to make all of us less exercised about the term exercise, about the nature of exercise. And the pun is very much intended, because exercised and exercise come from the same root. Before I go any further, though, I want to thank various folks who helped with this book-- my amazing editor, Erroll McDonald, and my agent, Max Brockman. And there's a whole suite of colleagues and students who've helped out in all kinds of different parts of the-- this book and read various chapters. I especially want to shout out to my wife Tonia, who read the whole thing from beginning to end, and my colleague and running buddy and collaborator in research, Aaron Baggish, who also read the entire book-- and we talked about it on endless morning runs-- and various other folks who help in all kinds of ways. I don't have time to thank them all individually. But really, I'm really grateful to all of them. OK. So the next 30 minutes or so, I thought I'd briefly talk a little bit about why I wrote the book and what it's about. And then, I'm going to give you several examples about some of the myths of exercise that I think make people exercised about exercise and explain a very strange modern, industrialized, commercialized, medicalized approach to something very natural. And I know it's a cliche. But cliches are usually cliches, because they're true. And I really was one of those pint sized nerdy kids who was picked last for every team. When I was a kid, I was very ashamed of my body. And I didn't feel very athletic. And I once actually hid in a closet during gym to avoid going to gym. And you can name every cliche you can think of. But that was me. I never thought I would become a somebody who would ever even work on this topic. But I did have an amazing role model, and that's my mother. Here's a picture of her recently. And that's, by the way, not a picture of her when she was younger, my father actually who takes lots of photos for some reason never took a picture of her running, because I guess maybe they were running together. But when my mother was a young professor at the University of Connecticut, they built a fancy new gym. And they wouldn't let women use it. And so she was so irritated by that. She started to run in order to liberate the gym. And she couldn't run even more than a quarter of a mile at first, but she slowly got up to a half mile and then a mile, et cetera. And she did liberate the gym, by the way. And she also became hooked on running and ended up running five miles a day for about five decades. She's still alive, and kicking, and very healthy, and vigorous, and exercises every day. And I attribute part of that to the fact that she was so physically active for most of her life. And so I grew up thinking it was normal to be physically active. But I was a-- I didn't-- that's not what I studied, right? I became a head guy, actually. So most of my career, I worked on skulls, and heads, and why the human head is the way it is. And I got interested in the topic of running, because I got interested in how and why we hold our heads still when we run. So humans are like pogo sticks when we run. We bounce up and down on two legs, and our heads are at the top of it. But most animals like this pig here, quadrupeds, and they can flex and extend their necks. And so we got interested in this topic of how humans can hold their heads still and keep it from joggering around when we exercise. And we thought there was this interesting structure called the nuchal ligament, which is a-- these have trace in the fossil record. And that led to my colleague Dennis Bramble and I writing this paper in nature in 2004 entitled "Born to Run," in which we made the argument that humans evolved to run long distances. And we've been doing that for several million years. And because of that, I got interested in barefoot running. Because if humans evolved to run millions of years ago, we obviously did it barefoot. And I was curious about how people used to run before the invention of modern shoes. And all that basically got me interested in the field of evolutionary medicine, which is the application of evolutionary theory and data to health and disease. And it's a fascinating growing and I think a very important new field. And it led me to write a book-- my last book, my previous book, which is The Story of the Human Body, which I published in 2013, which is really about the concept of mismatch or the theory of mismatch, which is that most of the diseases that we-- that get us sick and kill us-- COVID being an exception-- are our result from our bodies being inadequately or imperfectly adapted to modern environmental conditions. So flat feet, and myopia, and heart disease, and diabetes-- and the list is very, very long-- many cancers-- Most of us who are in this room or who are watching this talk at least are going to get sick and die from a mismatch disease. So it's pretty important. So anyway, I was thinking about mismatch diseases. And I was finishing up that book in 2012 when I went to do some fieldwork in the Sierra Tarahumara, which is in Chihuahua in northern Mexico. And I was doing research among the Tarahumara Native Americans who are well known for, among other things, their long distance running. It's really beautiful place. And I was driving around on a pickup truck to these really remote pueblos and measuring people's feet and talking to folks and being a good anthropologist. And I had my list of questions I was asking everybody. And I expected to see people running everywhere barefoot and-- But actually didn't see anybody running anywhere at all, except I asked them to. Nobody was barefoot. But then eventually I got to visit and see one of the amazing races that they do. In fact, there were two races I saw. And I've now been several times, and I've seen quite a few of these. But the first is it was actually a double header that day. So it began with what's called an ariwete, which is the women's race, which the women have a cloth circle which they flick with the sticks. They chase it, find the cloth circle. And they flick it again. And they run, and they flick, and they run, and they flick. And they do about 25 miles. It's a beautiful race and gorgeous to see and impressive running abilities. And then, the men's race starts after that. That's called a rarájipari, in which instead of a wooden-- a cloth circle, they have a wooden ball, which they flick with their feet. And then, they find it, and they run to find it, and they flick it again. And they run, and they flick, and they run, and they flick. And they do it. And this particular race went on for about 50 miles, really amazing race. And I was, of course, very impressed by these races, but also interested by the fact that only a few of the Tarahumara were doing this. The vast majority were just watching, like me. I did run along with them, actually, a little bit at night. And so I got a chance to measure an interview and talk to some of the-- to runners. And one of them was this guy named I'm going to call him Ernesto. He was in his 70s. And this is actually a picture of him in the rarájipari. I was taking a video of people. And I was trying to talk to him, and asking about his running and whatever, and asked him about how he trained. And I had been asking everybody this question. And the woman who was helping me interpret, because I don't speak the native Rarámuri language, was really struggling to get people to answer my question, because it turns out there's no word-- not only a word for training, but the idea of training is foreign to the Tarahumara. A few of them are great runners. Most of them actually aren't. And so Ernesto, eventually, when she explained that this gringo who's talking to you goes for like a five mile run every morning to practice his running, he asked me-- and I'll never forget this question-- but he said, why would anybody run if they didn't have to? And of course, it dawned on me that running is weird, actually, for-- just for the sake of running and that physical activity is a normal thing that people have been doing for millions of years. Physical activity's just moving, right? It's moving, expending energy to move. But exercise is a very special physical activity. And it's a modern strange thing that people just haven't didn't-- do before, because exercise is voluntary physical activity to sustain or improve health and fitness. It's a modern abnormal behavior. Nobody did it until recently. People didn't go for five mile runs in the morning just for the sake of it. People didn't buy weights whose sole purpose was to be lifted. They were physically active, because they had to be. Or they were physically active when it was rewarding and fun, like for example dancing, which the Tarahumara also do in beautiful ways. So to me, the apotheosis of exercise is the treadmill. Just think about it. It's a really weird thing, right? You spend thousands of dollars to buy one of these things, or you go to a gym, pay-- I don't know how much money you pay a week. Or maybe Google, it, provides you with one of these things. But somebody paid a lot of money for a machine that's loud, and noisy, and boring, and sometimes treacherous. And you get nowhere at all. Right? It's really a bizarre thing. In fact, in our research, because most of the research I do is in Kenya, we've tried to bring treadmills up into the area where we work. And if you've never been on a treadmill for your whole life and all of a sudden in your 40s or 50s, and somebody brings up a treadmill and asks you to stand on it, you're going to be very awkward. Right? It's a very strange and unpleasant thing. And in fact, in case you don't-- if you hate treadmills, you're not-- you're in good company. Treadmills are actually invented in the 19th century by the Victorians to punish prisoners. They're invented by, again, William Cubitt to keep people like Oscar Wilde from enjoying themselves in prison. So on all, I think today many people are exercised about exercise, where they're vexed, and worried, and anxious, and harassed. And no topic has really introduced me more to this fact that people are exercised about exercise than the barefoot running debate, which I got involved with back in the day when we published our research on barefoot running, because there was this incredible debate about whether barefoot running is better, or it's bad for you, and whether shoes are good for you. And people, of course, were worried about whether running would ruin their knees, and how much they should run, and how do you get motivated, and how much weights you should do, versus cardio, and how much sleep should people have, and is your chair out to kill you? And there's so many questions that people are confused about in terms of exercise. And for the most part, people just are unhappy about it, which is expressed by the fact that 80% of Americans don't get minimal amounts of exercise, even though the vast majority of them would like to. So we're not obviously doing very well. And as I said before, the biggest problem is that the vast majority of us are not getting our recommended minimal dose of 150 minutes a week. Again, that's just 21 minutes a day. That's not a terribly large amount. And I think the other problem-- There are other issues as well. We have become overly focused on weight loss. We focus a lot on elite athletes. But I think the other problem with the exercise is that we have this Western postindustrial bias. Almost all the data that we get-- we have about physical activity and exercise comes from studying Americans and Europeans. And yet, that's like a sliver of humanity, about 10% of the world, and doesn't represent what we were like for most of our evolutionary history. Right? So we have a very strange medicalized, commodified, industrialized, Western view of exercise and physical activity. And the result is that that's surprising. Not surprisingly, I think we have a very strange attitude towards it. And so I thought it would be useful and helpful to write a natural history of physical activity, including exercise. And there are really two mantras which guide my book. And the first is that nothing in biology makes sense except in the light of evolution. And that's because our bodies weren't engineered or designed. They evolved. And if you want to understand why our bodies are the way they are, you have to understand that evolutionary story. But we're also humans with complex behaviors. And if you want to understand something about behavior, you need to think about that human behavior in the context of anthropology. And so the book weaves together a lot of my own experiences. I've spent the last 15, 20 years traveling around the world seeing how people use their bodies, but also using information from anthropology, and various branches of biology, and health science to tell the story, the natural history, of human evolution. And I do so in four parts, because you can't be physically active all day long. To understand physical activity, you also have to understand inactivity. So the first part of the book is actually about physical inactivity, your resting metabolism, and sitting, and sleeping. And then, the next part of the book is about speed, and strength, and fighting, and sports that most animals are really good at, but we're actually not so good about that. But what we humans are exceptional at is endurance. And so the next part of the book is about walking, and running, and aging, and dancing, and all kinds of other endurance activities. And then, the final section of the book is about how we apply all that to modern health in the modern world. And so I talk about motivation, and dose, and the effects of exercise on disease. And each chapter isn't really about a myth. But I use some of the myths of exercise with it for each chapter. And I'm not going to go over all the myths right now, because I don't have time. But I thought it would be fun for the rest of this talk just to highlight a few of these myths and go into a little bit of detail. And as I said before, the biggest myth of all is that we evolved to exercise. And the way I think-- I like to think about this is what I call the myth of the athletic savage. We have this idea that-- and the modern world has basically contaminated us in that if we hadn't grown up with Nike shoes, and Gatorade, and cars, et cetera, we'd be these incredible athletes able to run ultramarathons, and dance all night long, and lift giant rocks over our heads, who knows what, right? And it is true that until the invention of modern machinery, if you were a hunter gatherer or subsistence farmer, you basically had to work for a living. And people engaged in lots of walking, and carrying, and digging, and climbing, and running, and dancing, and all kinds of other activities. But it turns out it's not a crazy amount. If you actually look at what hunter gatherers do, in terms of moderate and vigorous physical activity, it actually amounts to only about a little over two hours a day, about 2 and 1/4 hours. And so that's not an enormous amount of physical activity. It's more than your average American. But it's not a crazy amount of physical activity. And just like us, they spend most of the day resting. And if you look at when they're physically active, they're active primarily when it's necessary, in other words, to get food, or when they find it socially rewarding, as in, for example, this particular-- this dancing that you can see from the hunter gatherers in the Kalahari Desert. So if you've ever been in an airport, or a subway stop, or a mall, or whatever, where there's an escalator next to a stairway, and you have that little voice in your head that says take the escalator. Now, obviously, there were no escalators in the stone age. So there's nothing natural about taking an escalator. But it is natural to try to avoid unnecessary physical activity, because until recently, energy was limited. People didn't have a lot of extra energy. And so we had to engage in trade-offs. Energy you spend on a five mile jog in the morning, that's 500 calories. It's 500 calories that you're not spending on the only thing that natural selection cares about, which is having babies, which is reproducing or taking care of your body. And so I think we need to be more compassionate about this basic instinct people have, which is to save energy and not do unnecessary physical activity, because it's a fundamental normal instinct. And we shouldn't make people feel bad about that little voice. It doesn't mean you should obey that little voice. But this woman who I photoshopped going up the stairs is actually being abnormal in a way from an evolutionary perspective. So let's look at four other myths, just-- And again, I've just picked four of them. There are lots of stuff in the book, of course. But I wanted to pick four that I thought would be fun to talk about. And one is sitting, because probably most of you right now are sitting. And we've all been told to be terrified of sitting. Sitting is the new smoking. Your chair is out to kill you. And it's true. There's all kinds of horrifying statistics you can read about regularly in the newspaper. If you sit more than three hours a day, explains about 4% of the deaths in the world. And an hour of sitting is as harmful as the benefit of 20 minutes of exercise. And I could fill the screen with various other horrifying statistics. And yet, if you go and do what I do, which is travel around the world and see how people use their bodies, people sit all the time everywhere, in every culture. So the scene on the left that you see is a Hadza camp. That's actually the picture I took on my iPhone the second I walked into that camp. That's the first thing I saw when I walked on this camp. And look, everybody's sitting. That's what they do. This is the elderly Tarahumara gentleman, who's sitting, and people in the village in Africa, where they're all sitting. People sit all over the world. There's nothing unusual or normal-- strange about sitting. So actually, if you're curious, this is a Google talk. I thought I would use Google and ask how many hours a day do Americans sit? I did this two days ago, and up came a whole bunch of answers. And you get like so many different results. These are the top five hits. So one in four of us sits for more than eight hours, which is not a particularly useful statistic. According to one site, we sit 15 hours a day. another site says 6.5 hours a day. Another site, 6.4 hours a day. Another site, 13 hours a day. How do we believe this? And who are these people? And is it self-reported data? What are the covariants? Was it on weekends or weekdays? Et cetera, et cetera. Of course, it's really very hard. And in fact, there's a lot of really bad data out there. And a lot of people say all kinds of stuff. But if you look at high quality data, where they put accelerometers on people to actually measure what they're doing, and you look at age and various other sorts of things, and weekends versus weekdays, it turns out that young Americans sit around 9 to 10 hours a day, and older Americans tend to sit more, about 12 to 13 hours a day. But there's an enormous amount of variation, depending upon what day of the week it is, and your age, and your sex, and your socioeconomic status. And you can imagine other kind of variables as well. Now, you may think that Americans are sitting this ridiculous amount. But actually, it's no different from hunter gatherers. A recent paper by some colleagues and friends of mine actually just showed that the Hadza, who are a hunter gatherer population in Tanzania, sit about 10 hours a day, which is about the same as Americans of the same age. So there's nothing special about Americans in terms of how much we sit. But we do sit differently, and that's where it gets interesting. So if you're living in a population a part of the world where there's no chairs, and that's where I work, for example, there are no chairs with backrest. People sit on the ground. And so that means you have to use back muscles, and they often squat. So they have to use those muscles, and they often sit intermittently. The average bout-- the average time that they spend sitting at a given time is about 15 minutes. Whereas, we-- and I had to put these two favorite people on the planet here up on the screen here, but they look so excited and happy. But we sit-- tend to sit it chairs with backrests. And we don't have to use basically any muscles to support our upper bodies. And Americans tend to sit much more long-term bouts of sustained bouts, about 40 minutes for each bout. So we sit more passively. We sit less actively. And in fact, if you look at the data, what it really shows is not that work time sitting is all that bad for you. It's leisure time sitting. So various studies in Japan, and in Denmark, and other countries have shown that negative health outcomes are much more strongly associated with leisure time sitting than work time sitting. So if you sit all day at work but go home, and exercise, and walk to the bus stop, and all those other sorts of things, you're in pretty good shape. But if you work all day, sitting, and then you go home, and you spend the rest of the day sitting, well, then, of course you're going to get into trouble. And furthermore, the length of time that you spend sitting in each bout is strongly correlated with health outcomes, independent of how much time you spend sitting. So people, for example, who are sitting in long bouts without getting up, 30 minutes or more, have actually twice the rate of all cause mortality than people who sit in shorter bouts. So if you're going to sit, get up every once in a while. Get up every 10 minutes or so. Sit more actively. Let's not say that sitting is the new smoking. It's just not true. And by the way, there's a whole section of the book on slouching. If you've been told that you shouldn't slouch, it's basically all nonsense. It's we've been confusing cause and effect. So to speak, bad posture when you sit is actually more reflective of whether or not your back is strong. But there's no evidence that it actually causes higher rates of back pain. But you can check the book out to read about that. So I think we should be less exercised about sitting. It's not abnormal to sit as long as you get some physical activity. Just sit actively with interruptions and relax about your posture. If you slouch, don't worry about it. OK. So another common myth is that we evolved to be super strong. We have this idea that cavemen are these ripped guys with giant muscles, and they could lift giant barbells over their heads and stuff like that. And that myth actually goes back a long time. And in the book, I describe this fellow, Paul Du Chaillu, who was the first Westerner to travel to Africa and see-- and to see and describe gorillas for the general populace. And here is a picture of Du Chaillu lecturing in London about these terrifying creatures, which he grossly exaggerated. And it's not unsurprising that around the same time when people were first finding the first skeletons of Neanderthals that the Neanderthals were basically described to be a bit like those gorillas. And since then, we've had this idea that cavemen are ripped, super strong creatures. But actually, it's not true. And in fact, even our close cousins, the chimpanzees, aren't as strong as people often claim they are. Chimpanzees are about 30% stronger than most humans. And most hunter gatherers-- people have measured their strength-- actually aren't very strong. And furthermore, it's actually not even good for them to be super strong, because muscle is really expensive, right? But the thing that's important about them is that whether or not super strong, they tend to keep it up with their age. So this is a measure, for example, of grip strength in England for men and women, compared to a group of foragers in the Amazon, the Aché. And you can see that the Aché basically are track with 75th percentile for men and for women as well. But what's really cool about them is because they stay very physically active as they age, they tend to-- they tend not to lose strength that much as they get older, a little bit of course, which means that they avoid sarcopenia, which is really a dangerous disease. That's muscle wasting, which is a really important cause of frailty. And it causes a vicious circle. And the reason for that, of course, is that muscle is costly, as I said. If you're a typical scrawny human like me, about 30% of your body is muscle mass. And that accounts for about 20% of your metabolism. Now, if you bulk up to be like this guy, and you have about 40% of your body's muscle mass, you need another 200 to 300 calories a day to pay for all that extra muscle, which basically-- well, maybe it looks good, but it's not going to really benefit you if you're using weapons to hunt, or gathering berries, and that sort of thing. So it's actually a cost. And that's why we have this use it or lose it phenomenon. It's adaptation to gain strength when you need it and lose it when you don't need it. But now, today, when we-- people live these lives of physical inactivity, and they don't really have to do much strength, it becomes a mismatch. And that's why many of you may be aware of how Ruth Bader Ginsburg lasted till she was 87 strong and vigorous, because she went to the gym several times a week and stayed strong. And so as you get older, strength training is unquestionably a really very important to do about twice a week. So we should stop being exercised about strength. It's normal to just be only moderately strong, but it's also important to keep it up as you age. And you don't need, by the way, to go through this no pain, no gain nonsense to maintain your muscle mass and keep your bones strong. That's, if you want to look like Arnold Schwarzenegger, fine. But for the rest of us, that's completely unnecessary. So another myth out there is that you can't lose weight walking. And walking is important, because it's by far the most fundamental form of physical activity. Humans evolved to walk. That's what we are. We're basically apes on two legs. And around seven million years ago, that was the big shift that set us on a-- shift that set us on our evolutionary trajectory. And the average hunter gatherer woman walks six miles a day, and the actual average man walks nine miles a day. So typical hunter gatherer women are basically walking from like LA to Washington D.C. every day-- every year. That's an amazing normal, but normal fact. That's just normal to walk across the country, basically, that many miles every year. But it turns out that that's become a little bit controversial. And recently, there's been a trend to tell people not to bother walking or even exercising in general for weight loss. And the idea is that dining is much more effective than exercise for weight loss. And in many respects, it's completely true. If you walk a mile, you spend about 50 extra calories, which is way less than most of the foods that we crave after exercise. So if you got a bunch of fries, that's about 365 calories. You're going to wipe out any gains that you made. So we have what's called compensation. We eat. We eat more when we're hungry. We're hungry, we eat more after we exercise. And there's also some intriguing evidence that physical activity can affect your basal metabolic rate and actually lower it. But part of the problem with this argument is that a lot of the data on the effects of walking are based on that 150 minutes minimum level of physical activity that's often recommended. Again, that's the US Surgeon General's recommendation for how much physical activity you should get, which only about 20%, 25% of Americans actually get. So that's just 21 minutes a day. So basically, it's a mile a day. So if you actually get people to walk about 21 minutes a day, they can lose about-- if they don't compensate by eating extra food, they can lose about a half a pound a month, which can translate into about six pounds a year. And if your average American is trying to lose 50 pounds, sure enough. That's just not very effective. You're much better off dieting, then, if you want to lose weight. But if you took a-- take a more evolutionary normal dose, let's just double that to 300 minutes a week, which is just 40 minutes a day, still way less than your typical hunter gatherer. You can lose a pound a month, which is 12 pounds a year. And there are plenty of randomized control studies which show this is the case. So you're not going to lose huge amounts of weight super fast by exercising. But you can lose moderate amounts over long periods of time, which is very healthy. And even more importantly, physical activity is not so important for losing weight. What is really important for is preventing weight gain or weight regain. Here's an example of an experiment done here in Boston on policemen. And they put policemen on a really hard diet for like eight weeks. And some of them dieted. And some of them dieted but also had to do a serious exercise regime. And you can see that everybody lost a lot of weight. But the ones who exercised lost a little bit more weight than the ones who just dieted. Makes sense, right? But the key thing is that after the dieting was over, the dieters, just the dieters, stopped their diet. And they weren't exercising, and they gained all their weight back. But the ones who were on the diet and exercise routine and kept exercising were able to keep all that weight off. And study after study has shown the same thing. Do you want the real full benefits of a diet? Don't skimp on the exercise, and especially don't skimp on the exercise after the diet. It's your key to keeping the weight off from coming back again. So let's stop being exercised about walking. It's the most fundamental form of human physical activity. And it should be an important component of every weight loss program. And then, the final myth I want to mention is that it's common that we think about in our Western world that it's normal to be less active as we get older. We retire. We move to Florida. And it's true. And modern Americans get way-- if we're less-- if we're not very physically active in our normal middle age, boy, do we get physically inactive as we get older. So according to a recent big study of thousands and thousands of Americans, using accelerometers, so people in their 20s were engaged in about 24 minutes of moderate and vigorous physical activity a day. And by the time they're in their 60s, that's in half to about 12 minutes, which is not a hell of a lot. But I think that's actually a very abnormal thing, because back in the stone age, people evolved to be physically active as they got older. In fact, humans are unusual in that we evolved to live after the age at which we stop reproducing. So hunter gatherers, if they survive childhood, and infectious diseases, and diarrhea, and things like that, they actually typically live into their 70s and/or sometimes their 80s. So they're living about two decades after they stop reproducing. And they're not going into retirement. They're actually working hard as grandparents, foraging and hunting, and getting honey and all kinds of other things, and helping out their children and their grandchildren. So if you actually look at this study by a Kristen Hawkes company-- and Kristen Hawkes is the person who proposed first the grandmother hypothesis-- mothers in these foraging societies are actually working 2 to 5 hours a day getting food for their kids. Whereas, grandparents are actually working 48 hours. They're actually working harder. And that's important, because the stresses of physical activity, the reason exercise is healthy-- and I go into extraordinary detail in the book about this-- is that exercise is stressful. Physical activity is stressful. And it causes stress to your bodies in all kinds of ways. But that stress then turns on repair and maintenance mechanisms, which then clean up the mess. And in fact, like cleaning up a spill on the floor, you often make the floor cleaner than it was beforehand. And the same is true. So when you exercise, you're producing antioxidants and anti-inflammatories. And you're repairing cells. And you're repairing your DNA. And you're producing all kinds of growth factors for various organs, like your muscle, and your brain, your liver, and your bone. And the list goes on and on and on. Plus, you're also burning belly fat, which is very inflammatory. You're lowering your blood sugar, and levels of blood fat, and cholesterol. And again, the list is very long. So the important thing is that as we get older, physical activity becomes actually more important. And this was shown really clearly in this wonderful study. This is the first big epidemiological study of the effects of exercise on aging by Ralph Paffenbarger. It was done on Harvard alumni. And he did that because he figured out that universities like Harvard are fantastic places to study this problem, because they never lose contact with their alumni, because they're always trying to get money from them. And so we convinced the alumni office to let him get data on the alumnus on what their physical activity was like, and then waited for them to die, and then showed that for-- when alumnus were less than 50 years old-- they were the ones who were exercising a reasonable amount, 2,000 calories a week-- had 21% lower all cause mortality rates. But by the time they got into their 70s, the ones who were exercising 2,000 calories a week had 50% lower all cause mortality rates. And this has been shown over and over again in other studies. And it's also been shown that it's never too late to start. If you're sedentary when you're young, and you pick up exercise as you get older, you still get a lot of the benefits of the physical activity. And importantly, it doesn't really matter-- There's no one dose. Any exercise is better than none. This is a very important graph. This is the dose response curve of minutes per week of moderate to vigorous physical activity against the relative risk of death for a sample of well over a million Americans. And you can see that if you exercise just 60 minutes a week, moderate to vigorous physical activity, you lower your relative risk of death at a given age by about 40%. And as you get to 150 minutes a week, which is the standard recommendation, you go down to about 50%. And additional amounts of exercise continue to drop the curve. And eventually, of course, it levels out. So any exercise is good. And even if you just do a little bit, it'll give you enormous benefits. So of course, there's a lot more topics. I've only covered just a smattering of what the book is about. But I hope that the book informs, and entertains, and enlightens folks. But more importantly, I would hope that it changes the way we think about exercise, in particular in the science of health in general. I think we've oversimplified a lot of health information. And I think it's the information we get is also heavily biased. It's biased towards being Western. And it's often biased towards elite athletes. And it's biased towards weight loss. And it's heavily commercialized, and medicalized, and judgmental, and uncompassionate. And as a result, it's not surprising that the vast majority of Americans just don't like being nagged and harangued about it. And it's not succeeding in helping them get off the couch and be more physically active. And so I argue in the book that, we, by using an anthropological and evolutionary approach, we can help make exercise more fun and more necessary and also help people figure out how to make it more rewarding. But most importantly, I hope that the book helps people enjoy being active and helps us be less exercised about it. And with that, I'd be delighted to take some questions. PETE WILLIAMSON: So let's go ahead and go to the first question from the comments. So Steve Stepanian says, what are your thoughts on prolonged fasting and intermittent fasting? DAN LIEBERMAN: Ooh, great question. So intermittent fasting is actually one of the few non-exercise interventions that's been shown there's pretty good medical data that it has health benefits. And the reason I think it's beneficial is actually it turns on a lot of the same responses that physical activity does, because when you're in-- when you're doing physical activity, you're in what's called negative energy balance for a long period of time. You're using more energy than is coming in, obviously, unless you're gobbling huge amounts of donuts while you're running or whatever it is. But so you're in negative energy balance. That's a stress. And you have to draw on energy stores. And that activates all kinds of genes and cascades that turn out to have a lot of benefits. It turns out that intermittent fasting, essentially-- intermittent fasting turns on a lot of those same processes. And I think, again, it's because of negative energy balance. So of all the ideas out there about easy ways to get healthy, intermittent fasting seems to be the one that has the most evidence behind it, apart from exercise. And I don't think that's uncoincidental. That said, there's not a lot of good data. And there's no good data about the interactions between intermittent fasting and exercising. And I believe, I suspect when the studies come out that exercise will be shown to be a lot more generally beneficial than intermittent fasting. And if you're into exercising a lot, you don't really want to go through a lot of intermittent fasting. The two are incompatible. I like to run a lot. And there's no way I'm going to go through long periods of not eating food, because I'm just going to run out of gas. So I don't like to do it very much. But great question. Thank you. PETE WILLIAMSON: OK. Next question from Will Nicholson. Thanks for giving this talk, Dr. Lieberman! Have there been any significant developments since "Born to Run" for or against the endurance running hypothesis? DAN LIEBERMAN: Well, obviously, I'm biased, because I'm the author of the endurance running hypothesis. But I would say-- I think I can say quite without being unfair to others. But there's just been a mountain of evidence to support it. We now have genetic data. We have genes like the Cmah gene, which gives genetic evidence. We found so many different aspects of physiology, and anatomy, and biology, which predicted by the endurance running hypothesis. I don't think it's actually very debated anymore. It's entered the literature. It's a strange thing, because in science, we spend most of our time trying to prove each other wrong. So I think some of the arguments about endurance running have been really more about just how important it was in human evolution. And we never argued that humans evolved only to run long distances. Of course, walking still is really important. And not everybody ran. But I don't think humans could have become scavengers and then carnivores without running. And the traces in our bodies, vigorous physical activity is really important for us. And we have all kinds of adaptations, which make no sense without thinking about running. And they can't be explained in any other way. So I think it's a pretty resilient hypothesis. I'm going to stand by it. PETE WILLIAMSON: OK. Next question from Lisa Takehana. On the topic of dieting and caloric intake, how does cooking or baking affect the caloric value of food? And how does it affect the macro and micronutrients? DAN LIEBERMAN: So this has been an interesting topic. This is a good example of how people misuse evolution information. There's a lot of data on-- People have been studying raw foodists, like people who think that it's abnormal to cook our food. And the answer is you cannot be a human being in most parts of the world until very, very recently when-- unless you go to Whole Foods and stuff like that-- and survive as a raw foodist. Cooking increases your-- the availability, the bioavailability, of most nutrients. You get more calories out of cooked food. And also, you get more macronutrients out of them. Most of the arguments that cooking destroys the nutrient quality of food are just completely falsifiable. In fact, humans are so consistently-- Every human society cooks a lot of its food. And it's pretty clear that if you-- The only way you can get away with being a raw foodist is eating really high quality food that has had most of the fiber removed from it already. These are domesticated foods. There's no way you could be a hunter gatherer, eat a wild diet, and not cook your food. You'd die quickly. It's not sustainable. If you want to look more up about this, my colleague Richard Wrangham and Rachel Carmody, both at Harvard, have written extensively on this topic. And they're much more-- much greater authorities on this topic than I am. PETE WILLIAMSON: OK. Next question from Mike Digman. Hi, Dr. Lieberman. Exercise and dieting both seem important to overall health. However, calories in and calories used need to be balanced. How do hunter gatherers know when to stop eating? DAN LIEBERMAN: Well, it's not a problem for hunter gatherers, because they're-- they-- they-- First of all, they work hard. And they don't have huge amounts of excess calories. It's not like they go on diets. I think one of the funniest moments in my life-- Once, we were with some Hadza, and we were at the end of our trip. And we decided to cook up every last little bit of food we had and have a big feast. We had every little bit of every rice grain we had left in camp, we cooked, and all the bread. And the cook we had with us made a-- he made a cake, and he smothered it in jam. It was a high calorie meal. And I have never seen people carboload like that before in my life, because they were so excited to get all these great high energy carbohydrates, because until recently, people went through cycles of positive energy balance and then negative energy balance. And when you're in positive energy balance, of course, you store fat, but then you're going to take it back later, use it later, when you're physically active, when you're nursing. The average mother nursing is spending 500 calories a day to pay-- to synthesize all that breast milk. It's expensive. So hunter gatherers need that, to store fat, so that they can then use it for times of-- for times of when food availability is low, and they're at negative energy balance. So hunter gatherers don't diet. They don't restrict their food intake. They just eat as much as they can, because what they eat is actually what they need. And levels of obesity and overweight are essentially nonexistent among them. So the problem is that today we live in a world of plenty. We live in a world where all of a sudden, we can get all the rice, and cake, and shortbread, and fried chicken, and whatever it is you happen to like that you want. But we never evolved to curtail our intake. And now, we have to do something really as abnormal as exercising, which is to choose to eat low calorie foods. Imagine explaining to your great great grandparents that you pay more money for foods that have had the fat and sugar removed from them. That's pretty weird right. That's very abnormal. That's a very modern thing. PETE WILLIAMSON: OK. Next question from James Newman. As you say, we evolved to avoid unnecessarily expending energy. How do you recommend we counter this instinct and find motivation to exercise, given that fact? DAN LIEBERMAN: Thanks for asking that question. So chapter 11 in the book is entirely on that topic. And so I can't do it full justice. But I think there are several ways. As I said before, I think that we evolved to be physically active for two main reasons, for when it's necessary and when it's socially rewarding, when it's fun. And so I think the solution to motivating people, and if you look at the evidence, is that Fitbits don't work so well. Sorry, folks. Prescriptions don't work so well. Being nagged and bragged at, it doesn't work so well. But what does work well is when-- is social reward. So I think one way is to make-- is to treat exercise more like education. Think about education, which is equally abnormal. We never evolved to go to school, and learn algebra, and learn to read, and do all those sorts of things. So how do we make school-- how do we get-- how do we encourage people to learn things? Well, we make it fun. University's and school's fun. It's social. You see your friends. Of course, now in the COVID era, it's very unfun, as we all know. And we also make it rewarding in other ways. People pay like $60,000, $70,000 to go to my university and have me torture them. And I make them do all this stuff. And then, I grade them and give them a low grade if they don't do it to my satisfaction. And they're paying for the privilege of doing it. It's a commitment contract. So commitment contracts are another effective way. Some of you may know the website stickk.com, with stick with two k's .com. And a friend of mine actually, she wanted to walk more. She wanted to exercise more. So she gave stickk.com $2,000, made her husband her referee. And if she doesn't walk, I can't remember how many miles a week, like 10 miles a week, the website automatically-- and her husband doesn't affirm it, the website automatically gives $50 to the NRA. And it's been an incredible motivator for her to stick with her exercise regime, because she hates the NRA. And so she's kept with her exercise regimen. So that's another way of doing it. I think a commitment contract is effective, making it-- treating it more like education is effective. But for me, I think it's most effective by making it social. I run with friends. I have a running buddy who I have to meet tomorrow morning at 6:00 AM. And I can guarantee you tomorrow at 6:00, I do not want to be out there. It'll be cold. It'll be dark. It'll be miserable. I'd rather be in bed with my wife. But I can't leave him out there in the cold on the corner of Mass Ave at 6:00. So I'll have to get out of bed, and I'll grumble. And for the first mile, I'll be really pissed off at it. But eventually, I'll warm up, and I'll be-- And by the time we get home, I'm sure I'll be in a great mood, and I'm glad that I've done it. So I think people are good at exercising are good at finding ways to make it social. And the sociology of it, like dancing, and Zumba classes, or whatever you can come up with. People are doing all kinds of creative things on Zoom now in the pandemic. Those are over and over again have been shown to be the most effective ways to help people exercise. But instead of-- Because we treat exercise as something like cod liver oil. You get on your treadmill, and you do your 20 minutes. And you listen to some podcast, which makes it mildly tolerable. If that's OK for you, if you like that, that's great. But it's clearly not that enticing for the vast majority of human beings. PETE WILLIAMSON: So if I could jump in with a quick follow-on question to that. You said like getting together with your running buddies. But right now, we're in the middle of a pandemic. How safe is that? Is that safer than not exercising at all, or staying at home? DAN LIEBERMAN: Yeah. I'm not an expert on COVID. So I don't really know. It seems to me that there's very little evidence that people transmit the disease outside. What I've been doing-- And again, I'm not a doctor, so I can't give this advice. But I've been wearing a mask, and being careful, and trying to maintain some social distance. And I also get tested regularly. So that helps. And as does the person I run with. So he's a physician. So I relaxed about it. But you've got to figure out what you're comfortable with. But certainly, it's been harder to do that during the pandemic. It's a real challenge. But I should also mention that there's a lot of data which shows that physical activity is really important for priming the immune system to fight respiratory tract infections. And COVID is an RTI. It's a respiratory tract infection. It upregulates the number of the cells that are your first line of defense-- they're called natural killer cells; some of them are called cytotoxic T cells-- and also redeploys them to the linings of the lung and another very vulnerable locations in the body. And there's a fair amount of evidence that moderate levels of physical activity boost your immune system and also boosts your antibody production as well. So when you get the vaccine, go for a run. And the big debate really is whether or not too much exercise is problematic. So there's some evidence-- there's been some arguments that if you get excessive amounts of exercise, you use so much energy. You deplete the energy that's available to the immune system. And you depress it. And that's very debated. And I think if I were-- I'm being cautious. I'm trying to be careful about-- I'm not running marathons on regular-- regular-- regularly. And I'm careful afterwards, so I-- assuming that I'm vulnerable to infection. PETE WILLIAMSON: OK. Thanks. Let's move on to the next question. So it's Michelle Pham. Dr. Lieberman, we're seeing such an uptick in fitness and health technology devices and services. What do you think the next frontier will be for this sector? DAN LIEBERMAN: That sounds like a very Google-ish question. I don't know. I don't know. It's fun. Some of these fitness apps and devices are fun. I have a GPS watch. And I check my iPhone, which is very depressing during the pandemic, because my step count has really decreased, just because I'm not walking around town as much. But I'm still running a fair amount. I think the big question is really to what extent you can use these fitness apps to actually change people's behavior? And there's some evidence that there's some benefit. But there's not been the huge massive benefit that I think that we were initially told. If I were in your guys' shoes-- and if anybody wants to talk to me, I'd be happy to-- I think that really the way to use social media and to use some of these apps is not to focus so much on giving people information about how much they're exercising, but to work more on the social side, to help people-- help people have more fun. And my Fitbit doesn't make exercise more fun. It just reminds me how-- what a slob I am right now, doing nothing. So I think maybe that's-- If I were in the tech industry, that's what I'd put my money into. That's what I'd spend my effort on is trying to figure out ways to use technology to help people enjoy themselves and make things rewarding and happy to talk to anybody about that. PETE WILLIAMSON: OK. Let's move on to the next question. We have time for one or two more. OK. I'm not sure I can pronounce your name correctly, but from Kweku Taylor-Hayford. When practicing intermittent fasting, does meal timing have an effect? Is it better to skip breakfast than dinner, for example? DAN LIEBERMAN: Yeah. Look, first of all, I'm an expert on exercise and not on intermittent fasting. So I'm going to have to pass on that one. I would say yeah. You'd have to-- There's a big review article in the New England Journal of Medicine that just came out. I'm not sure there's a lot of really good data on that. But yeah. I'm going to focus on exercise, not intermittent fasting. But yeah. You'll have to ask the question elsewhere. If you do intermittent fasting, don't forget to also exercise. I don't think it's a substitute. Put it that way. Intermittent fasting, for example, is not going to really lower your blood pressure. PETE WILLIAMSON: OK. From Steve Stepanian. Is there a recommended optimal amount of how much to balance cardio and strength training? DAN LIEBERMAN: Well, one of my chief arguments in the book is to stop thinking about this word optimal when it comes to exercise. There is no such thing as an optimal. It depends on who you are, how old you are, whether you're male or female, how fit you are, what your energy-- what your injury background is like. Are you' worried about health disease? Are you worried about heart disease? Are you worried about Alzheimer's? Are you worried about diabetes? Are you worried about osteoporosis? Everybody's different. And for the most part, there's-- optimum, it seems that there's like a curve. There's an increasing benefit, and then there's a-- then there's a-- there's an increasing cost. But for most exercise, there's no evidence for that. There's actually-- It's a curve that goes like that, and it flattens out. And there's very little evidence that actually too much exercise is bad for you. And almost nobody's at those extremes anyway. So it doesn't really matter. So the answer is there is no-- there is no optimum. That said, a lot of experts recommend if you're going to do a minimum-- I think you can say there's a minimum-- is that you should, again, try to get that 150 minutes a week. That's a good reasonable minimum. And as you get older, it's really important to try to incorporate some strength training. And so the American College of Sports Medicine, and the Surgeon General, and others recommend that at least twice a week you do some-- you do some weights. But there is no such thing as an optimum. That's this part of this medicalization of exercise, which I think confuses people and gets people exercised. It's an evanescent, quixotic notion. There is no such thing. PETE WILLIAMSON: OK. I think we have time for one more question. So let's take the next question. So from Kevin Murphy. What was the most unexpected or interesting finding while you were researching the material for exercise? DAN LIEBERMAN: Oh, God. I don't know. There's so many bizarre and interesting things. It's probably easier to say what I thought other people have found most interesting. So here's one fact that seems to blow people's mind, which is that the average sedentary American is more active than a typical wild chimpanzee. And this is research that's been shown by various colleagues. I've been out and had a chance to watch chimpanzees, and I can vouch for that. We are cousins. The animals that we evolved from were couch potatoes. And that's actually a very important part of the story of exercise, because we evolved to turn up the dial and become much more physically active. And that's built into our physiology and built into our biology. And I think it's changed our-- us in very special ways. But there's so many other bizarre and interesting facts. I'm not sure. That's a tough question. But I hope that the book is full of interesting, and strange, and wonderful facts. But it's very hard for me to bring one right to my neocortex at the moment. Sorry. PETE WILLIAMSON: All right. Well, thank you very much, Dr. Lieberman. As a reminder, this is the book Exercised that just came out. So it should be available now at somewhere near you, either online or if you actually can find a store that's open, perhaps the store. And I also want to say thank you to all of us who are here with us on YouTube and asking the questions during the show. And I hope you all enjoyed it and got something out of it. Once again, thank you very much. DAN LIEBERMAN: Thank you. Thank you so much. [MUSIC PLAYING]
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Channel: Talks at Google
Views: 75,745
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Keywords: talks, talks at google, google talks, ted talks, inspirational talks, educational talks, exercising, health, stay active, workout
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Length: 54min 28sec (3268 seconds)
Published: Sat Jan 23 2021
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