“There is no point in running to the gym to lose weight before summer”

USimple logic suggests that the obesity epidemic that is sweeping through rich, industrialized countries is due to our increasingly sedentary lifestyles. It seems obvious that, since we do not spend an average of two hours a day in search of our food, crossing the savannah in search of prey or energetically digging arid land to extract wild tubers, as do for example the Hadza hunter-gatherers in Tanzania, we don’t burn enough calories and so we get fat.

So, with our connected watches, we heroically try to reach the magic threshold of ten thousand steps per day, we follow the injunctions to climb the stairs rather than take the elevator, hoping to both conserve electrical energy and spend energy. our body’s caloric energy, and we feel guilty when we haven’t made the most of our gym membership.

The idea is so simple that to question it seems completely incongruous, crazy, and even outrageous. However, as recent advances in evolutionary anthropology, supported by work in biology and public health, reveal, this idea is fallacious. It turns out that a sedentary Westerner addicted to screens burns as many calories a day as a hunter-gatherer, as Herman Pontzer already explained in 2017 in his article “The Exercise Paradox”, published in the magazine Scientific American.

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To reach this conclusion, Pontzer and his colleagues had their research subjects drink water containing two isotopes rare, then analyzed urine samples previously frozen and carefully transported from the Tanzanian savannah or the Bolivian forest to US laboratories. This technique makes it possible to measure the production of carbon dioxide and therefore the daily energy expenditure.

Metabolic constancy

They discovered that these measurements are identical to those obtained in a sample of « couch potatoes » Americans (literally “couch potatoes”, a term for people who move little), even taking into account differences in height, weight or age. Hadza men, like American men, burn about 2,600 calories a day, women about 1,900, regardless of lifestyle and step count.

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This metabolic constancy is not explained by the possibility that we have evolved separately from modern hunter-gatherers since the invention of agriculture five to ten thousand years ago. The conclusion remains the same when comparing individuals of the same ethnicity today, some of whom have been living in the city for a short time and others who maintain their traditional way of life. This metabolic constancy is not a human exception. Chimpanzees, sheep, and even kangaroos burn as many daily calories in captivity as they do in the wild.

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