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 human populations. This in turn supports the view that the current rise in obesity is due to increased food consumption, not decreased energy expenditure.
Perhaps obesity is primarily diet related, not in a simplistic calories-in/calories-out way, but in a type-of-food way. Could it be that the Federal food pyramid guide is the problem? Gary Taubes, call your office.