Daniel Lieberman (Allen Lane)
The words of gastronome Jean Anthelme Brillat-Savarin, 鈥淭ell me what you eat and I will tell you who you are鈥�, may have been published in 1825, but they are just as true today. What we pop in our mouths is crucial to our identity: do you avoid pork, go vegetarian, embrace the Mediterranean diet, eat palaeo, tuck into more or less meat, fat, vegetables, carbs or ultra-processed foods? The claims behind diets and food types are often contradictory, and whatever the choice, food will influence our health, energy and well-being.
Into this chaos comes , an evolutionary anthropologist at Harvard University. In his new book, Fed Up: What evolution reveals about food, diet and eating well, he uses his lens on this thoroughly modern agony of choice.
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Using archaeological research in early humans, work with modern hunter-gatherers and studies on some of our closest relatives, Lieberman shows that the evolved human disposition isn鈥檛 to stick to a few foods 鈥� despite what we might see in populations with historically limited local food options, such as Inuit peoples who relied heavily on fatty meat often from mammals such as seals.
Instead, our non-Arctic-dwelling ancestors adopted a flexible, opportunistic approach, eating whatever was edible where they lived. 鈥淥ur hunter-gatherer ancestors evolved to become the animal kingdom鈥檚 ultimate omnivores,鈥� writes Lieberman.
This means humans have a digestive system suited to great variety. Yet, many foods today are made from a few carbohydrates like wheat and rice, and many diets designed for general health or weight loss promote some food types while prohibiting others.
Lieberman also digs into the science of the most popular diets, trying many of them for two weeks, often with his wife, Tonia. This isn鈥檛 meant to be serious 鈥� it is a tiny sample run over too short of a time to assess health benefits 鈥� but it helps turn what could be a dry book into something more humorous and relatable.
A raw food diet, for example, results in frequent bowel movements and leaves the couple lacking in energy due to a calorie deficit. This and a fruitarian diet aren鈥檛 really shaped by any ancestral condition, despite what you may have read elsewhere. For example, the fibrous and often bitter fruits that chimps eat are very different from the sweet, sugary varieties we have bred over thousands of years. What鈥檚 more, Lieberman points out that while chimps eat mainly fruit, little makes them as excited as hunting and eating monkeys, and if given the choice, they pick cooked sweet potatoes over raw.
The meat-heavy palaeo diet, which avoids grains, beans and dairy, is based on similarly flawed logic. The real Palaeolithic diet was often a veggie feast, and Lieberman finds little evidence that avoiding foods like whole-grain bread, tofu and brown rice brings promised health benefits. He also investigates the Mediterranean diet, intermittent fasting, vegetarianism, veganism, factory-made liquid foods, diets low in fat but high in carbs and, alternatively, low-carb but high-fat, like the Atkins diet.
It鈥檚 a whirlwind ride, with Lieberman showing that when any diet excludes food groups, we should worry about missing out on nutrients. Overall, though, tend to fare better than those who eat more omnivorously, for example, by having a lower risk of diabetes, heart attacks and some cancers.
One of the main reasons these diets exist at all is an evolutionary feature that helps us put on weight: we are programmed to seek energy-rich foods, store surplus energy as fat, and hold on to that fat in case food is scarce in the future. Lieberman references examples from trips to study Hadza hunter-gatherers in Tanzania. One morning, they walked from wild beehive to wild beehive, smoking out each brood. In 3 hours, the hunter-gatherers 鈥済orged on more honey than I thought was humanly possible鈥�, he writes.
Such cravings mean that simplistic notions of using ancestral diets as targets is best set aside 鈥� unless you are likely to be relying on stores of fat to tide you over in fallow times or to fuel hunting for food by rather more energetic means than going to the fridge or shop, or ordering delivery.
Lieberman also neatly explains some of the powerful adaptations that stop us losing weight. Strict dieting or skipping meals can trigger the stress hormone cortisol, which as well as making us hungrier, can boost the storage of fat round the abdomen 鈥� the opposite of the intended effect.
Adding to modern problems, well-known evolved responses make us easy targets. Some ultra-processed foods are built on fat, sugar and salt, combined in specific quantities to light up neural pathways that reward you for eating them. As Lieberman says, 鈥淭hey are designed, manufactured, and advertised to be tasty, inexpensive, convenient, and to deliver what we crave.鈥�
Fed Up is an excellent and wide-ranging book, with the central message that no one neat idea will be the solution to what we should eat. Lieberman advocates not an ancestral diet, but taking the flexible, ancestral approach to finding food and applying it to our lives. We should, he thinks, seek identity not in a diet, but in an animal: the fox.
The fox has many ways to escape a hunter, but a hedgehog only one: curling into a spiky ball. Hedgehogs would stick to one diet, but the way of the opportunistic fox, says Lieberman, would be to embrace the contradictions in our knowledge about foods and health, and focus on variety while exercising moderation.
Readers wondering, as I was, which diet evolutionary studies would suggest we should eat to stay healthy as we age must wait until the very final page. And unsurprisingly, given official advice, it is lots of fresh fruit and vegetables, unrefined grains, some legumes, nuts, seeds and seafood, with not too much red meat, salt or added sugar, mostly unsaturated fat and no weird chemical additives.
Or, to quote journalist Michael Pollan (as Lieberman frequently does): 鈥淓at food. Not too much. Mostly plants.鈥�
Three great reads on food, health and exercise
by Samantha King and Gavin Weedon
This is a deep dive into the role of protein in our health 鈥� the latest nutrient subject to contemporary obsession. The authors are sociologists specialising in sport, health and the body: intriguing, rather than news you can use.
by David Cox
Can you slow down ageing by changing your diet? David Cox鈥檚 fascinating book attempts to understand what is accelerating our biological clocks and what we can do about those factors. He also experiments on himself.
by Daniel Lieberman
Most of us struggle to stay fit, because, as Daniel Lieberman shows in his earlier book, we never evolved to exercise: moving our bodies for hours every day was just鈥� life. Clearly, we need a major rethink.
Chris Simms is a writer based in Somerset, UK
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