Motivation Flagging? Running’s Evolutionary Biologist Explains Why That’s Normal

Daniel Lieberman’s latest book explains how in the modern world, our brains get in the way of exercise.

When Daniel Lieberman goes on research trips to remote locations in Kenya and Mexico, he’s the only one getting up to go for a run in the morning.

Why? In those cultures, people get plenty of physical activity as part of daily life; they don’t need exercise. But Lieberman, 56, a professor of human evolutionary biology at Harvard, has all the conveniences of modern life in America. He relies on running to get the physical activity he needs in a day, especially during the COVID-19 pandemic. (Plus, he likes it and is usually training for a marathon—his PR is 3:20:16 from the Bay State Marathon in 2015, and he has run the Boston Marathon 10 times.)

Lieberman writes about these contrasts in his latest book, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding.

Our bodies developed to work best with lifelong physical activity. But our minds “never evolved to get us moving unless it is necessary, pleasurable, or otherwise rewarding,” he writes. “Plunk us down in a postindustrial world, and we struggle to replace physical activity with exercise—an optional and often disagreeable behavior.”

The result is that 80 percent of Americans don’t get the WHO-recommended minimum of 150 minutes of physical activity a week. Lieberman explains why exercise can be hard to do, and he offers strategies on how to overcome the weak link of our minds.

In 2004 Lieberman cowrote a paper, “Born to Run,” which appeared in the journal Nature, and made him famous. He also figures prominently in the bestselling book of the same name by Christopher McDougall.

In a conversation with Runner’s World, Lieberman talked about his own struggles with physical activity during the pandemic, why runners should be sympathetic to those who don’t exercise, and why he rarely takes the elevator at his office.

This interview has been edited for clarity.

Runner’s World: Is it really so bad that most Americans aren’t getting enough physical activity?

Daniel Lieberman: That absence of physical activity comes with huge costs. Terrible costs. Seventy-five percent of doctor’s visits are for preventable diseases. And most of those diseases could be partially prevented by physical activity.

We’ve created a world where people no longer have to be physically active. Now we have to choose [to be active] rather than have to. There’s a reason most people don’t choose to do it.

What’s the reason?

You know when you’re in an airport or a mall, and there’s a stairway next to an escalator? You have that little voice in your head that says: Take the escalator. All of us. Some of us overcome that little voice. But even though there were no escalators in the Stone Age, that voice is completely natural.

People were physically active, and had to run and do various other things for millions and millions of years for two reasons only: when it was necessary (to get dinner or to avoid being someone else’s dinner). Or when it was socially rewarding.

It is a normal thing to avoid unnecessary physical activity. And we shouldn’t pretend otherwise. And make people feel bad for that little voice. We should just help them—rather than judge them.

Do you have that little voice?

Of course I do! I’m not a freak. My office is on the fifth floor of the Peabody Museum at Harvard. It’s an old building, so the flights of stairs are big. Every single day I walk into the museum, I actually have a conversation with myself as I get to the door of the museum not to take the elevator. Because I always want to take the elevator.

Why don’t you?

One of the main reasons I don’t take it—I like to joke, but it’s true—but if anyone sees me on the elevator, I’ll be branded a hypocrite. It’s a good motivator. Basically shame. I want to take it every day.

How often do you give in?

I’m pretty good. I take the stairs almost all the time. After a marathon, I let myself take the elevator for a few days, especially going down.

Your book explains how exercise—which you define as “voluntary physical activity that is planned, structured, repetitive, and undertaken to sustain or improve health and fitness”—is not something we evolved to do. So we should be gentle on ourselves when motivation wanes?

I think we should be compassionate. That’s the word I would use. Look, the readers of Runner’s World are not normal Americans in many respects, right? Economically and in terms of their physical activity levels. I tried to write a book that was as much for for non-readers of Runner’s World as it was for readers of Runner’s World. Because the people who don’t get enough physical activity, they get pissed off by people like you and me, because they feel sometimes a moralistic kind of association of exercise and virtue, right?

It’s hard to be physically active if you don’t like doing it. And we’ve turned it into this crazy virtue. Nobody until recently did what you and I do. At all the places I do field work, nobody gets up in the morning and runs five miles or 10 miles just for the sake of running five or 10 miles. Nobody. Zilch. This is completely modern, strange behavior. So let’s not pretend we’re born to run. We are born to run, but we’re not born to run for the sake of health and fitness.

If the message of the book is compassion, does that mean we can stop trying to convince people to exercise?

The first message is to be compassionate, but the second message is our society’s approach to exercise has by and large failed most people. We’re telling people—you ought to run!—or prescribing it, medicalizing it, commercializing it, commodifying it, selling it. Buy these fancy shoes and they’re going to make you want to run, or buy these exercise clothes and they’re going to make you want to run. It just doesn’t work. We know that it doesn’t work for most people. We need to try alternative approaches, and we need to be compassionate.

Each chapter of the book busts a particular myth—about exercise or sleep, for instance. We believe a lot of myths, apparently.

The way in which we present information about health and the science of health to the public is often dreadful. We oversimplify, and we get papers that tell you about one little study and then another study. And often the studies have contradictory results. People have no idea how to interpret the information they’re given. They’re given in poorly digested, poorly considered snapshots. People are confused.

Like the running shoe debate. One day they read they should be wearing cushioned shoes and the next day they read they should be wearing minimal shoes. You might read in one part of Runner’s World an article about the latest shoe evidence and then another section on Runner’s World which tells you the 10 best shoes of the year. It’s totally commercial.

What’s the solution to that?

I think we need to recognize that people are actually smarter than we think they are, and we need to stop making information clickbait. The public deserves better information. I think it’s a collective responsibility.

You can’t exercise all day long. There’s nothing abnormal or unnatural about sitting. Yes, of course, you sit too much, it’s not good for you. But to relate sitting to smoking, you read that and you realize it’s BS.

How has your own routine changed during your years of research?

I grew up thinking it was normal to run, because my mother started running. She’s definitely an inspiration. When I was a kid, I would run a little bit. I never ran for a team. It never occurred to me to compete. But I’m sure I would have been diagnosed as hyperactive today. I kind of figured out that running helped me stay a little bit calmer.

I was never serious until Dennis Bramble and I wrote the “Born to Run” paper. That paper started because for the first part of my career, I was studying the evolution of the human head. I got interested in the problem of how we hold our heads still when we run. And that led to this research that we ended up publishing that paper in Nature, which kind of changed everything.

We spent about three years writing that paper. As I was writing, I got more interested in running. The intellectual interest got the personal interest going and vice versa. It became like a feedback loop.

I first ran Boston in 2011, and I ran for charity the first few times, before I could qualify. I just finished my 10th. Now I’m able to just barely qualify.

What do you wear on your feet?

I wear different shoes on different days. In the winter, I’m a minimal shoe guy. These days I alternate between Topos and Altras. In the summer, I wear huaraches. I sometimes go barefoot but not that much these days.

The pendulum seems to be swinging yet again [back to minimalist shoes]. When I go to shoe stores, it seems like these super built-up shoes are becoming less common—it’s swinging back toward the middle. My mantra is: What matters is how you run, not what’s on your feet. I think we pay way too much attention to shoes.

Your book mentions sarcopenia—muscle wasting—in people as they age. Are you good about strength training?

Like a lot of runners, I like to run. I don’t get as much reward out of doing strength training. I try to do it, especially as I’m getting older. With COVID-19, I haven’t been able to go to the gym for almost a year now it seems. I try to do stuff at home—pushups and things like that—but nothing super serious.

I try to make it habit. For example, I like to make French press coffee in the morning. In the four minutes while the coffee is brewing, that’s when I do my pushups. That seems to work.

A lot of us are putting on weight during the pandemic. Any advice?

Three major factors that affect weight. The biggest is diet. The second is physical activity, which is not just exercise, but non-exercise physical activity. I’ve tracked my step counts for years now, and the pandemic has decreased my step count by about 50 percent, not including my running. That’s huge.

At-Home Workout Essentials

I think one of the mistakes people make is they think physical activity is just exercise; that’s not true. Non-exercise physical activity is incredibly important. That’s going to be contributing to people’s weight balance. Let’s say you’re still running your usual 30 miles per week or whatever, but you’re walking half as much. The average American walks about two miles a day. If you’re now walking one mile a day, that’s going to add up over time.

And the final issue is stress. A lot of us are experiencing an enormous amount of psycho-social stress, from multiple pandemics, COVID-19, but also political pandemics and social pandemics and racist pandemics. That just elevates your stress levels. Stress elevates cortisol. And cortisol causes you to a, crave food and b, to store food as fat. Cortisol promotes visceral fat storage—belly fat. Stressed people gain weight. All of this is combining together.

But of course, physical activity is not as effective as dieting for weight loss. Study after study has shown that. But it’s not negligible, either. It’s a factor. Plenty of data show it helps prevent weight gain and regain. Does it completely do it? Of course not. But it’s important. It’s part of a mix.

If your step count is half of what it was, do you compensate for that?

I’ve been trying. It’s hard! I can’t really up my running crazy amounts. Fortunately, I run enough that I think it’s compensating reasonably. But I’ve had to be much more careful about my eating, I’ve noticed. I’ve really had to try to cut back. I’m a classic runner—I go to the refrigerator and open the peanut butter jar and have a spoonful. That kind of thing. I really needed to cut back on that, to stem the tide.

We got a dog recently, and we’re walking him about an hour a day. I lost about four pounds in the first three weeks we had him, but then I gained it right back in the second three weeks. What’s happening?

Ultimately energy balance is all about energy in and energy out at some basic level. You can’t escape basic laws of physics and chemistry. Energy balance—the total number going in versus the total number going out—is complicated. But if you’re walking more, running the same amount, and gaining weight, it ultimately has to do with diet. There’s no other explanation. Unless we violate basic rules of thermodynamics.

I was afraid you’d say that. But in general for the runners, for those who already believe in the power of exercise, do we need to be gentler and less sanctimonious to our peers?

I do sometimes question the 26.2 bumper stickers. That’s virtue signaling. I wonder to what extent it pisses people off.

Let’s not pretend that running a marathon is some special kind of virtue. We do it because it’s fun, right? And we also like the training. It’s healthy for us. But you don’t need to run a marathon to get the health benefits of running. And certainly you don’t need to do an ultramarathon to get the health benefits of running. But running is part of who we are and it’s wonderful and there’s a reason why so many of us love it. Running helps make us human. Being physically active helps make us human.

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