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We all know why Americans are so fat, right? We too junk and we sit on our Duffs all day.
Perhaps not, a team of international researchers said now. Their new study, examining energy expenditure among one of the last remaining populations of hunter-gatherers of the world, seems to debunk our conventional wisdom -. At least in part
While we have always assumed that ancient human ancestors must have been more active than modern Westerners today - with our office jobs, our cars and our TVs to keep us sedentary - new measures the actual energy expenditure are surprising. They show that people in traditional societies feeding does indeed participate in more physical activity, but their total energy production is almost identical to that of Westerners pudgy today. This finding contrary to intuition is explained by the lower basal metabolic rate foragers :. They spend less energy at rest, even if you compare people of the same size and age
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to collect the surprising new measures, the researchers recruited 30 adults of society hunter-gatherer Hadza, a small population in the countries of Africa Eastern Tanzania. No company today is really like those of our ancestors tens of thousands of years, the researchers say, but the Hadza share some important similarities with our Pleistocene ancestors era.
In particular, the Hadza maintain a way of traditional foraging lifestyle, hunting on foot arcs using, small axes and digging sticks, and without modern tools such as vehicles or fire arms. They live the game they hunt and tubers, fruits and honey they collect.
To measure energy consumption, participation Hadza adults wore GPS units to track how far they traveled each day. They also wore monitors breathing at rest and while walking to measure their metabolism in every state. And a measure of total energy expenditure was calculated from urine tests that showed the speed with which the study participants could eliminate a chemically modified water given to them to drink by researchers. Then, these measurements were compared to similar measures of 68 men and women in the United States or Europe, and also data from the farming communities in Bolivia, Nigeria and Gambia in energy expenditure.
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Unlike even the expectations of the researchers, the scientists write, energy expenditure measurements Hadza looked pretty similar to measures elsewhere.
In fact, even if total energy expenditure was varied considerably by age, sex and body size, as expected, when the researchers looked at men of the same age who each weighed, say , 130 lbs., There was no discernable difference in lifestyle group in the total expenditure of energy daily. On average, the Hadza were much smaller than Westerners, both in height and weight (130 lbs. Was at the upper end to the Hadza men). But statistical analysis suggests that the fundamental relationship between energy expenditure and lean body mass - not including extra pounds of fat Westerners - was essentially the same in all societies, and through people, big and small
.These results are all the more surprising that the Hadza seems to spend a lot more energy to exercise, as they hunted and foraged. But the differences in activity did not translate into differences in total energy consumption. Moreover, even among members of the same company, Hadza who walked a long way every day are not total expenditure measurably higher than that of people who do not work so much. It seems that the metabolisms of people can compensate somewhat the level of activity.
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The new findings seem to contradict the popular belief that weight management is simply a question of balance between what we eat enough of targeted physical activity.
"The similarity [total energy expenditure (TEE)] among Hadza hunter-gatherers and Westerners suggests that even dramatic differences in lifestyle can have a negligible effect on TEE" the authors conclude in their study, which is published this week in the journal PLoS One .
Although the authors do not look at food in the details, they add that their findings suggest that the high energy consumption - eating too much - is responsible for the Western obesity epidemic rather than too little energy expenditure. However, they note that physical activity is known to have many beneficial effects on health, in addition to any role in weight management.
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Ultimately, what the authors of the study may have discovered is that people are more alike than we previously realized. Across radically different societies and landscapes, human bodies work similarly.
"We assume," they write, "that [total energy expenditure] perhaps, a relatively stable physiological stress related to the human species, more a product of our common genetic heritage our diverse modes of life."
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