Homo sapiens evolved to store fat efficiently rather than lose it through dieting, according to Daniel Lieberman.
Most mammals do not exceed 5% body fat, but lean hunter-gatherers carry roughly three times that amount, Lieberman stated in an interview with L’Express. Storing higher levels of fat functioned as an energy reserve to sustain three distinct metabolic demands during food scarcity.
These requirements included fueling a large, energy-demanding brain, supporting long-distance daily walking of 10 to 15 kilometers, and meeting the substantial energy costs of female reproduction and lactation, which typically demands 600 kilocalories per day.
“As l’obésité était inexistante ou extrêmement rare, nous n’avons jamais évolué pour perdre volontairement de la masse graisseuse, c’est-à-dire pour faire un régime,” said Daniel Lieberman, telling L’Express that modern diets conflict with biological adaptations designed for survival in scarcity.
Cooking transformed human physiology by allowing early populations to extract significantly more energy from food. This dietary shift enabled the development of larger brains and higher reproductive rates. Lieberman said that humans became biologically dependent on cooked and processed food to sustain their energy requirements.
Experiments with raw diets demonstrated the practical limitations of uncooked sustenance for modern humans. Lieberman told L'Express that raw eating proved intensely unpalatable, which highlights the evolutionary reliance on cooked meals.
The popular paleo diet relies on multiple misconceptions about ancestral human populations, according to research outlined in the book Fed Up: What Evolution Reveals About Food, Diet, Health, and Eating Well. Lieberman explained that natural selection shaped humans to maximize reproductive success rather than achieve optimal long-term health.
Archaeological and anthropological data show that hunter-gatherers consumed grains and legumes after applying preparation techniques like cooking and fermentation to reduce anti-nutrients. Historical foraging groups did not follow a single, uniform dietary standard across different regions.
Rising obesity rates stem from systemic changes in food availability rather than individual moral failure. Lieberman told L’Express that the proportion of Americans affected by obesity quadrupled during his lifetime as supermarket shelves filled with ultra-processed products designed for hyper-palatability and extended shelf life.
“La réglementation, les taxes et l’étiquetage ont été très efficaces pour réduire le nombre de fumeurs, et tout indique que nous pourrions faire bien mieux en taxant et en encadrant les aliments ultra-transformés les plus néfastes,” said Lieberman, pointing to tobacco control policies as a framework for public health interventions.
Global food production currently yields enough sustenance to feed the world’s population of 8 billion people. Distribution inequality remains the primary driver of hunger, echoing principles established by Nobel laureate economist Amartya Sen in 1998.
Cultural frameworks surrounding food, particularly the French art of communal dining, offer a sustainable alternative to restrictive dieting cultures. Lieberman told L’Express that moderation and shared meals align better with human social biology than rigid nutritional exclusion.
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