Harvard Professor: “I Tried Every Diet. This Is By Far The Worst.” - Daniel Lieberman - #1137

**Chris Williamson** (0:00)
You've spent years researching every major diet and trying many of them yourself. I want to go through and review all of those. But first off, what was that journey like?

**Daniel Lieberman** (0:11)
Well, it was fun. I mean, I've been working for quite a few years on a book about the evolution of diet.
And I thought rather than just simply studying them, which was the majority of the book, I thought I should try them as well. So kind of, you know, on and off as I was working on the book, my wife joined me for many of these diets. I kept trying some of these, you know, diets, some of them better, some of them worse, but just kind of give a little, first of all, some participant observations. So I got a sense of what these diets are like, but also to kind of add context and experience them for myself.

**Chris Williamson** (0:44)
What did you start that journey believing about food that you no longer agree with?

**Daniel Lieberman** (0:51)
Gosh, that's, I changed my opinions about so many things. I mean, the reason I started this book and this, this journey, as you say, is that I'm actually, my research is mostly on physical activity. I study the evolution of running and walking and throwing and various other physical activities, but I also teach nutrition and digestion and physiology and that kind of stuff. And I read the literature. And a few years ago, actually, with some colleagues, I taught a course on diet and exercise. And I've just been so confused by what I read, right? Because one, you can read it in the New England Journal of Medicine, you know, the arguably the top journal in the world, articles in the same year that tell you that saturated fat is good for you. And then articles that tell you saturated fat is bad for you. You know, this much salt is too much for you. And this much salt is actually just perfect for you. I mean, you name it, there is controversy and confusion. And so I wanted to explore those problems myself.
But as an evolutionary biologist, I wanted to integrate an evolutionary perspective, an evolutionary lens with hardcore biomedical data, cultural data, anthropological data, experiential information, all that together to think about it in whole.
So I was really trying to do this in order to answer questions for myself.

**Chris Williamson** (2:12)
What use does an evolutionary lens give you that is typically missed when people make assessments about diet and nutrition?

**Daniel Lieberman** (2:20)
Oh, gosh, it's hard to know where to start. There's a famous expression in my field that nothing in biology makes sense except in the light of evolution. It was written by a guy named Theodosius Dobzhansky in 1972 And what he meant was that we weren't engineered, we weren't designed, we evolved. And if you understand why things are the way they are, you need to take an evolutionary perspective. So evolution answers a lot of why questions. And when you start addressing why questions, you begin to think differently also about how questions and what questions.
So nothing makes sense except in the light of evolution, and diet is no exception.

**Chris Williamson** (2:55)
It feels like nutrition and diet are a little bit like new religions. There's dogma, it's a super sensitive topic, people get tribal, it's often impossible to change their belief no matter how much evidence you give them.
Why do you think that's the case? Why do people become so ardent?

**Daniel Lieberman** (3:13)
I completely agree with you. And in fact, I think that one of my biggest takeaways from working on the book was just how tribal people are about their diet. And I don't know the answer, but I suspect it has to go something along the lines of this, which is that for millions of years or thousands of years, depending on which time scale you want, people ate the way their culture dictated, right? If you lived in the Middle East, you'd eat like a Middle Easterner, and if you lived in Japan, you'd eat like a Japanese person. And now we live in a world where everybody kind of eats the same stuff.
And a lot of institutions are sort of crumbling, and I think people are searching for identity. And I think one of the ways in which we define ourselves is by what we eat or very often by what we don't eat, right? And that's been sort of the case all along. You know, if you're kosher, you don't eat this.
If you're Jane, you don't eat that, et cetera, et cetera. But I think people are searching for meaning and identity, and diet is a really important way of defining it. A lot of diet, some diets are kind of like cults. I mean, they're sort of online.