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We all know why Americans are so fat, right? We eat too much junk and sit on our duffs all day.
Perhaps not, a team of international researchers now says. Their new study, examining energy expenditure among one of the world’s last remaining hunter-gatherer populations, seems to debunk our conventional wisdom — at least in part.
While we’ve always assumed that humans’ ancient ancestors must have been more active than today’s modern Westerners — with our office jobs, our cars and our TV sets to keep us sedentary — new measurements of actual energy expenditure are surprising. They show that people in traditional foraging societies do indeed participate in more physical activity, but that their total energy output is almost identical to that of today’s pudgy Westerners. This counterintuitive finding is explained by the foragers’ lower basal metabolic rate: they expend less energy while at rest, even when we compare people of the same size and age.
It seems that people’s metabolisms may compensate somewhat for activity level. The new findings seem to contradict popular beliefs that weight management is simply a matter of balancing what we eat with enough purposeful physical activity.