Daniel Lieberman: Key Moment: Harvard Professor Reveals The Biggest Lies About Exercise & Weight Loss!

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00:32In the first chapter of your book, you say that you went to visit the Native American tribe, the Tarahumara. They are famous for their long-distance running. What did you learn about running from them?

00:44Well, they have been famous for well over 100 years. Many people have gone to study the Tarahumara and have commented on their amazing ability to run. But what I really learned from them is that for them, physical activity is spiritual.

01:05There is the book *Born to Run* that describes their running and calls them a hidden tribe of super-athletes. They are not hidden, and they are not super-athletes. The one thing that the book missed was that the main impetus for the famous long-distance races they do is that it is a form of prayer.

01:30It is a beautiful metaphor for life, and it is also an opportunity to bet and play sports; it is all wrapped into one. What I learned was that this actually used to be almost universal among Native American tribes. Everybody had long-distance races and ball games, and they all had a spiritual element. They have simply retained their traditions because they are in a very remote part of Mexico that is essentially inaccessible. We all used to do this; all humans used to do this. In fact, if you look around the world, every population has a tradition of endurance events.

02:12Some of the subject matter you talk about in your book, and also outside of it, is how we used to run. I went to the podiatrist the other day because I got this pain in a point on my foot—plantar fasciitis. It was an ongoing pain, and they prescribed me some insoles. They measured my foot and said, "Basically, you are standing wrong, your arch is a bit too flat, take these insoles and wear them in all of your shoes."

03:00I always think in these moments when someone prescribes me something that is not natural: why? Where did I go wrong? Who lied to me to the point now that at 30 years old, I have these insoles because, presumably, my ancestors did not have them?

03:29Plantar fasciitis is what I would call a mismatch disease. It is a disease that is more common or more severe because our bodies are inadequately adapted to modern environments. In your case, as is the case with a lot of people, you have a weak foot.

03:52You look like you go to the gym and are a pretty fit person. I will make a bet you strengthen pretty much every muscle group in your body except your feet. One of the reasons is because we encase our feet in stiff-soled shoes that are very comfortable. The reason the shoes are comfortable is that your foot muscles have to do less work when you are using those shoes.

04:18Your foot has four layers of muscles in it, and those muscles are supporting your arch. At the bottom of those four layers of muscles is this layer of connective tissue, the plantar fascia. The problem with the plantar fascia is that if it stretches too much, it gets inflamed. It has almost no vascularization, so it is very hard for it to repair itself when it gets inflamed.

04:45To prevent plantar fasciitis, the best way is to have a strong foot. A strong foot is a healthy foot. So, the way to treat the disease in the long term is to strengthen your foot. But if you want to alleviate the symptoms, that is what your podiatrist did. By giving you an insole, it is basically preventing your arch from collapsing as much, making it more comfortable so your plantar fascia gets stressed less.

05:15That is a typical example of what I call "dis-evolution." It is what happens when you treat the symptoms of a mismatch disease rather than their cause. Podiatrists are a bit like drug pushers in that respect because they are essentially putting your foot in a cast, and for the rest of your life, you have to keep using them unless you strengthen your feet. There is nothing wrong with treating the symptoms—pain is no fun—but also work on strengthening your foot and the plantar fasciitis will disappear and never come back.

05:49The plantar fasciitis has now healed after about a month of wearing the insole. I no longer have the insoles with me here in New York because I have also taken a bit of time off running. I was playing a lot of football. So now I am at the preventable stage. You said to strengthen my foot; how does one do that?

06:14Good question. There are some foot-doming exercises and things like that. But the other way is to wear more minimal shoes—shoes that aren't stiff-soled and don't have arch supports. Go barefoot a lot. That will naturally strengthen the muscles in your foot because you will have to use those muscles.

06:40Have you ever gone for a long walk or run on a beach, and afterward your feet are tired? The reason your feet are tired is that you are now walking on a compliant surface; it is not stiff, so your muscles have to work more to stiffen your foot to push you forward.

06:58Wearing shoes that aren't as stiff-soled will slowly strengthen your foot. But—and this is a huge "but"—if you do too much too fast, your plantar fasciitis will come roaring back and you'll hate me.

07:18I actually have these Vivo Barefoot shoes. You have the same shoes on!

07:22Great shoes. Those are the exact kind of shoes that will help strengthen your feet.

07:28These are a fairly new addition to my life, and they feel really strange because you can kind of feel the floor.

07:34Yes, but you have to transition. If you have a weak foot, and you suddenly make that the only shoe you wear all the time, you will probably regret it. Slowly increase the percentage of time you wear them. If you suddenly decide to lift huge weights you couldn't lift before, you will hurt yourself. Same thing with your feet.

08:00This goes back to everything else you have said about how choosing comfort, like a nice supportive shoe, has actually just deferred a problem into the future for me. It is the same with diet and being sedentary. When you choose the easy road in the short term, you pay the price later.

08:45There is another myth that you bust, which I think a lot of people use as a reason not to run. They say it is really bad for your knees.

08:58Oh man, that gets me so mad. I hear this from doctors all the time. Now, it is true that knee injuries are the most common running injuries, but arthritis—which is what they are usually talking about—is absolutely, definitively not increased by running.

09:20Arthritis is caused by cartilage wearing away in a joint. It is a myth that running actually increases cartilage damage. If you have arthritis, running is excruciating and problematic. But if you don't have it, running actually may be slightly preventative.

09:37Joints, like everything else, benefit from being used. Physical activity actually helps promote strong and healthy joints. We used to think they just wore away like tires on a car, but now we know that physical activity promotes repair mechanisms in cartilage just as it does in other tissues in the body.

10:04The other thing about running is that I think a lot of people run incorrectly today. That is why we started studying barefoot running a few decades ago. If humans have been running for millions of years, most of that time we were running barefoot. So how did people run before shoes?

10:24Today, shoes have these cushioned heels that enable you to essentially run the way you walk—you land on your heel. People who are barefoot often land on the ball of their foot and then let their heel down. It is called a forefoot strike or a midfoot strike. When you do that, you actually prevent your foot from crashing into the ground, causing a collisional force.

10:52If you were to take your shoes off and run up Lexington Avenue here, I guarantee you would not be landing on your heels; within a few steps, you would start landing on the ball of your foot because it hurts less. That is how we evolved to run—in a way that doesn't involve slamming into the ground with every step.

11:15That causes less force around your knee. The trade-off, though, is that it is harder on your ankles. Your calf muscles and your Achilles have to do a lot more work. So people who switch from heel striking to forefoot striking often get Achilles tendon problems or calf muscle problems if they don't do it properly. You have to switch gradually and slowly and build up strength.

12:15So would you recommend, if you can, to run more barefoot? Especially if you have those kinds of shoes we just discussed?

12:25I think what matters is how you run, not what is on your foot. A "barefoot style."

12:30How do I learn to run in a new way, though?

12:35There are some tricks. A barefoot style tends to be a high stride frequency—roughly 180 steps per minute. Relatively short strides so you're not throwing your leg out. The most important thing is not "overstriding." If you ask any coach on the planet, they will say overstriding is bad.

13:06Overstriding is when you throw your leg out way in front of you and land. That leg is a stiff leg, which means more force and it's harder on your knees. A good runner lands with their shank, or their tibia, vertical. Your ankle is below your knee. When you do that, pretty much everything will work out properly. It will mean you won't land hard on your heel, and your leg will act like an excellent spring.

13:56What do you think is the best kind of cardiovascular exercise for the promotion of good health? I have been doing some CrossFit stuff, some HIIT workouts. I have been trying not to run as much because of injuries.

14:23You do HIIT workouts pretty much every day?

14:26Pretty much every day. We track it with a group of friends. Whoever does the least workouts every month is evicted. We've done it for three and a half years.

14:47Well, the best exercise is the one you like doing. But you have to mix it up. There is no one perfect exercise. You want to have a mixture of low, slow intensity and some high intensity. You want to have some strength training and some cardio.

15:10Cardio is the bedrock of exercise; it promotes the most health benefits. It is good for burning energy, your cardiovascular system, and controlling inflammation. But we've tried to medicalize exercise, like there's a proper dose. "Take this pill this many milligrams this many times per week." Exercise doesn't work that way. There is no optimal dose. Everybody is different depending on what you are worried about, whether it's heart disease, Alzheimer's, or depression.

16:19A lot of people exercise because they believe it will help them lose fat.

16:24Ah, one of the biggest debates on the planet. I've had multiple people come on this podcast and say a whole range of things about weight loss and cardio.

16:40It's sad that it's such a debate, but that's how science works. Part of the explanation for the debate is: what dose are you analyzing? Every major health organization in the world recommends that you get 150 minutes per week of physical activity. That is what the World Health Organization considers the division between being sedentary versus active.

17:25A lot of people struggle to get 150 minutes a week. So, a lot of studies prescribe 150 minutes a week of walking and then look at the effects on weight loss. Guess what? When you walk 150 minutes a week—which is 20 minutes a day, about a mile a day—you're not going to lose much weight. You're basically burning about 50 calories a day doing that. That is a piddling amount of calories compared to drinking a glass of orange juice.

18:05So, surprise, surprise, those kinds of studies show those doses are not very effective for weight loss. However, plenty of rigorous, controlled studies that look at higher doses—300 minutes a week or more—find that they are effective, but not fast and not in large quantities. You're never going to lose a lot of weight really fast by exercising. A cheeseburger has 800 or 900 calories; you have to run 15 kilometers to burn the same number of calories.

18:45Physical activity can help you lose weight, but it’s not at the low doses often prescribed. But the one thing we do agree on is that physical activity is really important for helping people prevent themselves from gaining weight or, after a diet, from regaining weight.

19:14One of my favorite studies was done in Boston on policemen. They got a bunch of policemen on a really severe diet. They all lost weight. But some of the policemen had to diet and exercise, and some just dieted alone. The ones who dieted plus exercised lost a little bit more weight, but then they tracked them for months afterward. Most people, after a diet, have the weight come crashing back. The policemen who kept exercising after the diet was over were the ones who kept the weight off.

20:06Have you seen the show *The Biggest Loser*?

20:08Yes, where people go to lose weight. These people lost ridiculous amounts of weight. Kevin Hall at the National Institutes of Health studied them for years afterward. Most of them regained a lot of the weight they lost. There was one person on the show who did not, and that was the person who kept exercising. Physical activity's other important benefit when it comes to weight is preventing weight gain. Why is it an "either/or" between exercise and diet? Diet is the bedrock for weight loss, but exercise should be part of the mix.

23:01What is the most important thing we haven't talked about, Daniel?

23:03I think the most important thing is that we need to be compassionate towards each other. There is so much shaming and blaming and prescriptions. The reason I entitled the book *Exercised* is that we make people feel "exercised" about exercise. We make them feel uncomfortable, unconfident, and shamed.

23:30People may look at you and think, "Gosh, I wish I was like him, but it's just not me," and they may feel put off by our conversation. I think we need to emphasize that if you put a chocolate cake and an apple in front of me, I would want to eat the chocolate cake. In my building at Harvard, my office is on the fifth floor. Every single day I want to take the elevator. The only reason I take the stairs is that if anybody catches me in the elevator, I’ll be a hypocrite.

24:30We make people feel bad for taking the elevator. They shouldn't feel bad; it's an instinct. We have to figure out ways to help people without shaming them. You don't have to swim the English Channel or run a marathon. Taking the stairs in your building every day—anything is better than nothing.

25:25That leads me to the reward system. I am really looking forward to my run tomorrow morning in Central Park. When I run, I'm going to get a big dopamine hit. My body is going to produce all this dopamine, which is the molecule that says, "Do that again." Gamblers get dopamine hits; people who eat chocolate cake get dopamine hits.

25:55But if I were unfit and overweight, I wouldn't get that dopamine hit. When people start exercising, they don't get the reward that people who are fit get. And then they're made to feel bad—"You didn't enjoy your run around Central Park?" Well, it takes months, if not years, before you actually get that reward.

26:16Really?

26:17Yes, because just like being overweight causes you to become insensitive to insulin, you become insensitive to all kinds of other hormones and transmitters, and dopamine is one of them. So it's not an instant benefit. It's hard. We need to be compassionate towards people who are struggling to become fit. We need as a society to help those folks rather than judge them.

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