Hunter-gatherers, Westerners use same amount of energy, contrary to theory

July 25, 2012

Modern lifestyles are generally quite different from those of our hunter-gatherer ancestors, a fact that some claim as the cause of the current rise in global obesity, but new results published July 25 in the open access journal PLoS ONE find that there is no difference between the energy expenditure of modern hunter-gatherers and Westerners, casting doubt on this theory.

The research team behind the study, led by Herman Pontzer of Hunter College in New York City, along with David Raichlen of the University of Arizona and Brian M. Wood of Stanford measured daily energy expenditure () among the Hadza, a population of traditional hunter-gatherers living in the open savannah of northern Tanzania. Despite spending their days trekking to forage for wild plants and game, the Hadza burned no more calories each day than adults in the U.S. and Europe. The team ran several analyses accounting for the effects of body weight, body fat percentage, age, and gender. In all analyses, daily energy expenditure among the Hadza hunter-gatherers was indistinguishable from that of Westerners. The study was the first to measure energy expenditure in hunter-gatherers directly; previous studies had relied entirely on estimates.

These findings upend the long-held assumption that our hunter-gatherer ancestors expended more energy than modern populations, and challenge the view that obesity in Western populations results from decreased energy expenditure. Instead, the similarity in daily energy expenditure across a broad range of lifestyles suggests that habitual metabolic rates are relatively constant among . This in turn supports the view that the current rise in obesity is due to increased , not decreased energy expenditure.

The authors emphasize that physical exercise is nonetheless important for maintaining good health. In fact, the Hadza spend a greater percentage of their daily on physical activity than Westerners do, which may contribute to the health and vitality evident among older Hadza. Still, the similarity in daily energy expenditure between Hadza hunter-gatherers and Westerners suggests that we have more to learn about human physiology and health, particularly in non-Western settings.

"These results highlight the complexity of energy expenditure. It's not simply a function of physical activity," says Pontzer. "Our metabolic rates may be more a reflection of our shared evolutionary past than our diverse modern lifestyles."

Explore further: Evidence lacking for sleep length, energy metabolism link

More information: Pontzer H, Raichlen DA, Wood BM, Mabulla AZP, Racette SB, et al. (2012) Hunter-Gatherer Energetics and Human Obesity. PLoS ONE 7(7): e40503. doi:10.1371/journal.pone.0040503

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3 comments

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Lurker2358
not rated yet Jul 25, 2012
We probably spend more of our energy on brain power and stressors.
antonima
not rated yet Jul 25, 2012
Being in a state of high stress is well known to contribute to, often unwanted, weight loss. It makes me wonder whether this proves westerners are at performing at the edge of their possibilities in terms coping with stress. If we are burning just as much calories on that as hunter gatherers are on physical exertion, it may mean that we are at the limit of what our bodies can put out?
mrlewish
5 / 5 (1) Jul 27, 2012
I suspect that the researchers didn't take into account the amount of processing the "western diet" undergoes. While on paper the calorie count may be the same processed food takes less energy to digest.

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