Daniel Lieberman
Daniel Lieberman is Edwin M. Lerner II Professor of Biological Sciences and a professor of the Department of Human Evolutionary Biology at Harvard University. He received degrees from Harvard and[…]
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Why modern fitness culture misunderstands human bodies
“It’s this modern idea of doing voluntary discretionary, physical activity for the sake of health and fitness.”
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19 min
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Daniel Lieberman
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For most of human history, movement was inseparable from survival. Deliberately burning energy for no immediate purpose would have made little sense in a world where calories were scarce and bodies were costly to maintain.
Seen through an evolutionary lens, exercise stops looking like a personal shortcoming and starts looking like a cultural invention we’re still learning how to live with, says Daniel Lieberman.
DANIEL LIEBERMAN: So the word exercise, you know, comes from the Latin ejercicio. And it meant, you know, to train so we still do math exercises or soldiers do exercises to get fit. But eventually the term has changed it's meaning and it's developed new meetings. So one hand it means to do voluntary physical activity for the sake of health and fitness. That's the kind of sort of fitness, physical activity kind of exercise. But on the other hand, it's also means, you know, to be exercised means to be upset, to be confused, to be anxious, to be kinda worried, you know, we get exercised by our math exercises. And so I, to me it's part and parcel of the strange concept of exercise, right? It's this modern idea of doing voluntary discretionary, physical activity for the sake of health and fitness. But we don't do it often. You know, most people don't do it 'cause they want to, they do it because, you know, it helps stave off death and decrepitude and in the modern world, of course, a lot of people are confused about it 'cause they find it hard to do, they're not quite sure how much to do. There are all kinds of myths surrounding it. So very much people are exercised about exercise today. And really I think that by shining the light of evolution and using kind of an anthropological perspective, my goal really is to help people be less exercised about exercise.
- [Voiceover] How evolution made us move.
- I would say that the definition I use of exercise is pretty much the bog standard definition that people in the sort of fitness exercise science world use, it's important to make a distinction between physical activity and exercise. So physical activity is just moving, right? When you do anything, right, go shop, you know, pick up your groceries and take them to your car. That's physical activity. When you, you know, sweep the kitchen floor, that's physical activity. But exercise is discretionary, voluntary physical activity for the sake of health and fitness. So it can include everything from sports to running on a treadmill to going for a walk. I think the paradox of exercise is that everybody knows it's good for them. I don't know that really anyone who says they don't want to ever exercise, right? But the paradox is that most things that are good for us kind of want to do, you know, but exercise is kind of the reverse, right? It's something that we all know we want to do. It's good for us, and yet a lot of us have a hard time doing it. And the proof is in the data. According to the CDC, only about 20% of Americans get the very minimum levels of exercise that every health organization in the world thinks is the minimum for an adult, which is 150 minutes a week. So 80% of us really struggle and fail to get very basic amounts of exercise. But almost everyone says that they want to get enough exercise. The most common reason that people don't like to do exercise when you ask them, is that they don't have time. You know, they find it stressful and they're busy, right? And that's a legitimate concern for a lot of people. Imagine if you have to commute a long distance, you have a job that you know is very sedentary. You gotta, you know, deal with your kids in the evening or maybe you have two jobs or whatever, you know, it's very challenging for people to exercise and to find the time in the modern world. The other reason that people often give for not exercising because they don't like to, they find it uncomfortable. They find it unpleasant. They find it, you know, they get hot and bothered and they don't feel like they get much reward out of it. And so there's a lot of inertia that prevents people from doing it. They have a hard time getting off the couch. And, you know, I think we need to be compassionate towards both of those reasons, right? Because yes, people are stressed for time and yes, it is often unpleasant and unfun but we make them feel bad about that, right? We make them feel bad for being stressed. We make them feel bad for having that inertia when actually it's completely normal. I mean, nobody ever exercised in the stone age, right? People were physically active when they had to be, and they might dance or do other sort, play, you know, do other things that were for fun. But you know, but volitionally going on a five mile run in the morning or going to the gym to lift weights whose sole purpose is to be lifted, that's a really strange, weird, modern behavior and there are all kinds of instincts that we have not to do it. And we shouldn't make people feel bad for having those instincts. Instead, we should help them figure out ways to overcome those instincts because we live in a world where we now, because we've mechanized everything, right, we no longer have to be physically active. We now, in a very strange way, have to choose to be physically active. And that's not so easy. Oh my gosh, there are so many myths about exercise. It's hard to know where to start. But I would say that, you know, one myth is that our ancestors were sort of just natural, incredible athletes who just get up in bed in the morning and you know, run ultra marathons at will and without ever much stress or difficulty that our ancestors were really incredibly strong. That there's a trade off between speed and strength. That you don't have to, you know, that it's normal to be less physically active as you get older. That there's a perfect type of exercise, perfect amount of exercise, that sports equals exercise. I could go on. The topic of exercise is just laden with myths. A common view about our sort of evolutionary origins and about sort of the evolution of physical activity is that we evolve from these kind of super athlete kind of ancestors and that on civilization has sort of contaminated us. So if you wear shoes or you drink Gatorade, or you have a fancy watch or something like that, somehow that kind of deprives you of the kind of natural talent that you have. And if only you had been born in some little village somewhere and didn't have TV and didn't have access to all these commercial goods that you'd be a natural, incredible athlete and that you could just get outta bed and you know, run an ultra marathon or something like that. A lot of these myths, to be honest, stem from I think this idea of this Rousseauian idea of the myth of the noble savage, right? That humans uncontaminated by civilization are also sort of naturally good and fine. And they also come from terrible, horrible racist stereotypes about, for example, you know, Africans not experiencing pain as much and you know, Asians having some kind of natural sort of proclivity to sneak around in the dark, you know, I mean, we all know these stereotypes and they're pernicious and they're wrong. But they've been applied in various ways to hunter gatherers and to subsistence farmers in various parts of the world to make us feel that somehow they're like these kind of basically fundamental super athletes. And when you do that, I think you do harm to both, to people all around the planet. You do harm to those populations because you kind of dehumanize them. I mean, when they run an ultra marathon, it's just as hard as when I were to try to run an ultra marathon. They sweat, they toil, they get nausea, they get cramps, they do it because not because it's easy for them. They do it because they value it, they think it's worth doing. And you also make people in the west feel terrible. Like somehow there's something wrong with them, right? And they should throw away their shoes and you know eat a paleo diet or something like that, and all of a sudden ta-da they'll become this like amazing athlete. And that's just not true. That's just a myth. And it's pernicious in a variety of ways. In 2012, I had that good fortune to be invited to go to the Ironman World Championships in Kona in Hawaii. It's an amazing event, right? And if you don't know what an Ironman, full Ironman triathlon's like, you start off with a 2.4 mile open water swim, then the athletes rush out of the water, jump onto bikes with these like high tech helmets and stuff like that. They speed off and they do 112 mile bike ride across the desert. And then they come back, throw off their bike, jump off their bikes, and then they do a full marathon in the heat. It's like 90 degrees Fahrenheit, right? And it's really amazing. And the elite athletes do this in a little bit over eight hours. They're just like cyborgs. They're not like human beings. It's astonishing to watch. And the less lesser athletes take longer to do and everybody has to finish by 17 hours, so by midnight. And it's just astonishing to see people put their bodies through that kind of endurance to achieve something like that. And I was really impressed by that. I'd never seen a full Ironman before. And then just a few weeks later, I was in a very rural part of Mexico in Chihuahua up in the Sierra Tarahumara where I got to observe a Raráhipri which is the traditional foot race that the Tarahumara Native Americans do. And it's almost like a soccer game. There are two teams and they have a little ball, a little round ball that's carved out of wood that morning, and there are about five people on each team, and they kind of kick the ball with their feet and then chase it and find it, and then kick it again and chase it and find it, kick it again. There's like a little circuit they do. And there are two teams, and whichever team lapse the other team wins. And the race I saw must have been about 40, 50 miles long. And so it's another incredible endurance event. And on the surface you'd say, oh my god, these events are totally different, right? Ironman is very commercial and everybody's wearing the fanciest latest gear and they've got super fancy shoes and they drink, you know, they're using gel and goo and all kinds of specially formulated nutrition drinks, and their bikes cost like, you know, $10,000 $20,000 and it's very commercial, right? And they're speakers and crowds, et cetera. Whereas the Tarahumara, when they're running, they're just wearing the clothes that they normally wear, they're running in sandals. It's very uncommercial. And you think, oh my gosh, it's so different. You know, one is more authentic than the other, but if you stop and think, actually they're very similar, right? Because both involve rewards, right? So Ironman, there's like, you know, the winner and the winner gets a prize, et cetera. Well, the Tarahumara also have prizes. They bet huge amounts of stuff, right? They bet clothes and goats and corn and stuff like that. They don't have Gatorade, but they make their own kind of form of Gatorade out of corn. And they cheer on their runners too. And there's the joy of victory and the agony of defeat and all that. So in some ways they're very different, but in other ways it's kind of the same thing, you know? And it's a personal journey that people undertake. A very small number of them. The vast majority of people are observers. They're not participants. So really it made me realize that oh yes, there are some differences between sort of more modern, commercialized western forms of endurance physical activity. This is something basic and fundamental that all cultures do. And actually I think what makes us similar is greater than what makes us different. You know, there are different kinds of training, right? You know, play is a form of training in a way, right? You know, children play, right? Because they're learning skills, they're developing capacities and humans are one of the few species, dogs are another that continue to play as adults, right? And that play helps us maintain our capacities. It helps us with social relationships. I mean, there's all kinds of good things that happen with play, right? But exercise is kind of very, I wouldn't say exercise is generally play, although some play is exercise. And when you kind of exercise in order to, you know, or train for like an event, you're doing something, you're spending a lot of energy. You're doing physical activity kind of to get ready for something, right? And certainly, you know, for the kinds of things that we do, again, that's a very modern western behavior. So when I was talking to, and I've talked to Native American runners who participate in these, in these long distance races, when I asked them how they get ready for the race, how they train, they would kinda look at me like they didn't understand the question. There was, you know, what are you talking about? And so, you know, I was working with a translator. The translator was saying, you know, this gringo, you know, like runs five miles every day to kind of get ready for a race. And the question that I got was, you know, why would you run if you didn't have to? Because their life is their training, right? You know, when I ask people there or ask people in Africa, in the places where I work, when do you run? The most common answer I get is, oh, well, to chase a goat. You know, that's the most common answer I get. There are a lot of ways to quantify how physically active somebody is, right? And a very simple one. It's not necessarily the best one, but a simple way of doing it it's what's called the physical activity level. It's just a ratio. So it's the total amount of energy you spent in a day divided by the energy you would spend if you were just at bed rest, what's called your basal metabolic rates. The energy you spend just taking care of the most basic essential functions of your body. And so say if you're in bed rest in a hospital and lying in bed with just like a clicker for the TV and you're doing absolutely nothing, not even digesting food, your physical activity level would be about at your power, physical activity level it would be about a 1.2. And if you're like a tour de France cyclist, it would be above three. If you're kind of a desk worker, it would be like 1.6. So it's kind of a way to compare individuals but also species because it's standardized your body size, 'cause your body size essentially determines your basal metabolic rate. And it's interesting that most animals have physical activity levels of about two to three. So they're, you know, pretty active. We evolve from apes. And turns out that primates in general, and apes in particular have really low PAL's, really low physical activity levels. Chimpanzees have physical activity levels about 1.4. And so their physical activity levels are actually lower than sedentary American. So your average sedentary American who doesn't really do much and you know, spends most of his or her time on in chairs and you know, et cetera, and takes elevators and all that is still more physically active actually than your average chimpanzee. Whereas hunter gathers, people who every day have to go out and get their food, their physical activity levels tend to be around two, about 1.92. Subsistence farmers who don't have a lot of machines and tractors and stuff like that, they're may be a little bit harder working maybe 2.1, 2.2. And it wasn't until the industrial revolution that people's physical activity levels would be able to go down like about 25% to 1.6, 1.7, which is sort of typical of your average American. So it's a useful kind of simple standard to help us compare just generally how active , different groups or different individuals are. So your basal metabolic rate is a really important number because it tells you kind of just how much energy you're spending on just the essential maintenance of your body, you know, paying for your brain and paying for all the tissues in your body. And you know, you have to turn over tissues all the time. Like the cells in your gut are being replaced like every five days or so. I mean, your fingernails are growing, everything's happening in your body, right? And that all costs energy. And it turns out that a kind of typical say, adult male, my size, right? I'm not all that big, but you know, it spends about two thirds of his or her physical metabolism just on basal metabolic rates. So I spend about 1600 calories a day just existing, you know, just taking care of my body. So the vast majority of the energy that we spend isn't spent on running around and being physically active and moving. It's actually spent on just maintenance, just basic total maintenance. And that's one of the reasons why we can never evolved not to be, you know, all that physically active when it wasn't necessary. Because until recently, energy used to be limited, right? It wasn't like, you know, 7-Eleven's or Dunkin' Donuts or Whole Foods or whatever your favorite place to get food is around the corner. You know, if you wanted something to eat, you had to go find it. You had to either, you know, hunt it or gather it or dig it up. And so energy was limited. And when energy is limited, you have to engage in trade-offs, right? And so if you spend energy on physical activity, that means you're not spending energy on taking care of your body or reproducing, which is what the only thing natural selection really cares about. And so the fact that our bodies are so expensive helps explain why we tend to avoid unnecessary physical activity because it prevents, like for example, this morning I went for a five mile run. So I spent about 500 calories. Those are 500 calories that I could have spent on my metabolism. And if I were energy limited, that would've been a bit of a problem, right? Which is why people who are energy limited and already physically active, it makes no sense for them to go for a needless, completely pointless five mile run in the morning. So technically a calorie is the amount of energy it takes to raise one gram of water, one degree centigrade, right? So it's a unit of energy. And so we convert various kinds of energy into calories. There are of course, other units of energy like the joule for example. But calories are kinda a useful one and it's 'cause we all our food is labeled in calories. So calories is the most common one. But actually the calories that we mostly talk about that are on our food labels are actually kilocalories. They're actually a thousand calories. So when you look at a label for a chocolate bar or a can of beans or something, and it says there are 50 calories, this actually means that there are 50,000 calories, right? But anyway, that's neither here nor there, but that's fine. But so most of the time we're talking about calories with a capital C or kCal, kilocalorie. And you know, our bodies use a lot of calories. Typical human body spends about 2000 to 3000 calories, or in this case, kilocalories a day existing. That's your basal metabolic rate. Plus all the energy you spend, you know, running around, doing chores, making dinner, whatever it is you do for your day. When you go for a walk, you probably spend an extra 50 calories per mile. If you go for a run, you're spending probably an extra 100 calories per mile for that run. So that kinda gives you, hopefully gives you a sense of sort of what kind of energy amounts we're talking about.
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