From paleo to intermittent fasting: are any diets actually good for us?
episodePreviously titled “Do any diets actually work?” — renamed by the publisher on Sep 22, 2026
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What is the central question about what we should eat and why is it so confusing?
This is the Guardian.
What should we eat? It's a simple enough question, but as the options multiply, the answer feels more and more confusing. From vegan to paleo, low carb to low fat, each attracts its own bunch of evangelical devotees, all claiming that the science is on their side. But can one diet really act as a magic bullet for health, weight loss and longevity? And can our distant ancestors' diets offer any clues? Today I'm speaking to evolutionary anthropologist Professor Daniel Lieberman. From the Guardian, I'm in Sample and this is Science Weekly.
Daniel Lieberman, you're an evolutionary anthropologist and professor of biological sciences at Harvard University. Now, usually you study the evolution of human physical activity, but for your new book, Fed Up, you've turned your attention to food. Why?
Well, it's the next thing, you know. I mean, I can't tell you how many people ask me, you know, what's more important, diet or exercise? And uh the answer is both, obviously. And I teach physiology and uh at Harvard and I teach nutrition and just like everybody else, I'm confused about the whole diet world out there. And I I wrote it partly because it's sort of a sequel to my last book, Exercise, but also From my own curiosity, I want to, you know, evaluate all the different evidence out there about diets and and think about it from an evolutionary perspective.
To test some of these diets, you and your very patient wife, Tonya, tried each one for two weeks at a time. I'm gonna ask you about some diet myths, starting with this idea that to be healthy we all need to eat like early humans. People have heard this called the paleo diet, but remind us what does that actually involve eating?
Paleo diet, like all diets, it has a germ of a good idea, right? Which is that, you know, obviously we're adapted to certain foods and we're not adapted to other foods. And so the idea behind the paleo diet is that we should eat like our ancestors, because presumably we're adapted to eat that way. But in general, it's a high protein diet that bans junk food. Um that's good. Um, but it also completely bans legumes, so no beans, no lentils. You're not allowed to have any grains, so no No wheat, no oatmeal, no rice, even if it's brown rice or whole grain foods, and you're not allowed to eat any dairy. So there's a lot of elimination. You know, so some aspects of the diet are pretty good, some aspects I have some serious problems.
How does the paleo diet define “ancient” eating and what foods does it actually eliminate?
And you know, people might expect you to be kind of all for this kind of diet. You've spent time with hunter-gatherer communities, you've eaten with them. But I'm interested in how much that sort of paleo diet does resemble what our sort of Paleolithic ancestors would have been.
Well, that's one of the big problems. So the idea that our ancestors never ate grains or or or beans is just silly. It's just wrong. I mean, we have lots of evidence from the archaeological. I mean, we have even starch granules on the on, you know, the teeth of Neanderthals and things like that. In my lab, actually, we've done some analyses. We've studied all the diets of all the major hunter-gatherer groups in the tropics, uh, for which there's good data. And And you name it, they ate it. I mean, we evolved to eat anything, not for the sake of health, but in order to have as many babies as possible. And uh if it can crawl or fly or swim, uh if it grows and not won't kill you immediately, our ancestors ate it.
And as you're saying like the paleo diet encourages people to avoid something which I know is a a staple food for you and that's peanuts. Almost every episode we do here on the podcast on on health seems to end up with us telling people to eat more legumes. So why the hate for them from the the paleo people? I mean, uh or do we need to stop shilling for big bean or whatever?
So part of the paleo diet elimination of legumes, of beans and peanuts and things like that, is that there was this mistaken idea that our ancestors didn't eat them. It's actually there's a bean called the marama bean, for example, it's the number two food in the in the Kalahari Desert among the hunter-gatherers there.
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Chapters
8 chapters
1
What is the central question about what we should eat and why is it so confusing?
0:00–2:51
2
How does the paleo diet define “ancient” eating and what foods does it actually eliminate?
2:51–5:15
3
Why do paleo advocates ban legumes and grains, and are those bans scientifically justified?
5:15–7:22
4
What is the real story behind saturated fat myths and what does the evidence say today?
7:22–9:16
5
How effective is intermittent fasting compared with traditional calorie‑restriction diets?
9:16–11:07
6
Which diet did Daniel Lieberman find most sustainable after testing many regimes?
11:07–13:20
7
What does the “fox vs. hedgehog” metaphor mean for everyday eating choices?
13:20–15:24
8
What practical take‑aways does the episode offer for listeners seeking a balanced diet?
15:24–17:17