July 27, 2012
Hunter-gatherer Study Proves We’re Not Fat Because We Sit, But Because We Eat
Lee Rannals for redOrbit.com - Your Universe Online
Despite what some choose to theorize, when looking back on our ancestors, our society is not growing obese due to the change in cultural lifestyle when compared to those in the hunter-gatherer days.Some believed that because modern lifestyles were different from those of our hunter-gatherer ancestors, then it could be the cause of the global rise in obesity. However, a study published in the journal PLoS ONE found that there is no difference between the energy expenditure of modern hunter-gatherers and Westerners.
The team measured daily energy expenditure among the Hadza, which is a group of traditional hunter-gatherers living in the open savannah of northern Tanzania.
Although the Hadza people spend much of their days trekking long distances to forage for wild plants and game, they burned no more calories each day than adults in the U.S. and Europe.
The researchers looked at the effects of body weight, body fat percentage, age and gender. They found that in all analyses, daily energy expenditure among the Hadza hunter-gatherers was indistinguishable from that of the Westerners.
The study is the first to measure energy expenditure in hunter-gatherers directly, whereas previous studies relied on estimates.
The findings contradict previous theories that our hunter-gatherer ancestors expended more energy than modern populations, effectively challenging the view that obesity in Western populations results from decreased energy expenditure.
The researchers believe that the similarity in daily energy expenditure across a broad range of lifestyles suggests that habitual metabolic rates are relatively constant among human populations. This supports the theory that the current rise in obesity is due to increased food consumption, not decreased energy expenditure.
The Hadza spend a greater percentage of their daily energy budget on physical activity than Westerners do, which may contribute to the health and vitality found among other Hadza.
The similarity in daily energy expenditure between Hadza hunter-gatherers and Westerners suggests that the U.S. and European culture have more to learn about human physiology and health.
"These results highlight the complexity of energy expenditure. It's not simply a function of physical activity," Herman Pontzer of Hunter College in New York City, who led the research, said. "Our metabolic rates may be more a reflection of our shared evolutionary past than our diverse modern lifestyles."
He suggests that spending more energy on something like physical activity means you also spent less energy on something else you would´ve been doing instead.
Pontzer said that even if we had the same lifestyle as our ancestors did, we would still be taking in more energy than burning, because we are eating a lot more today than we need to be.
"We are not saying that physical activity is not important for health — clearly it is — but it does not appear to be the main cause of obesity," he wrote in the journal.