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Obesity linked more to diet than inactivity

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Metabolic Cost of Living in Human Foragers  (Washington University)

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Obesity in U.S. and European adults may be more a consequence of diet than lifestyle, according to an international research team funded by NSF. The researchers reached this conclusion after assessing energy expenditures of Hadza hunter-gatherers living in Tanzania.  The Tanzanian expenditure was indistinguishable from that of Westerners.

After measuring daily activity levels with wearable GPS and heart rate monitors and carbon dioxide output, the researchers found that the Hadza had a greater physical activity level than Westerners (U.S. and European) and were lean; however, their average daily energy expenditure (kilocalories burned per day) was similar to people in Western populations, as were their metabolic rates when walking and resting. 

The findings run contrary to current explanations for obesity that suggest people in developed countries burn fewer calories than people following  a more active lifestyle. This study suggests that obesity in the U.S. and other developed countries may result primarily from over consumption, rather than a decrease in physical activity. 

The research also indicates that total energy expenditure may be a fixed human physiological trait. If this is the case, populations in the developing world that are transitioning to more highly-processed, energy dense foods common in Western diets may experience higher rates of obesity and metabolic disorders, such as insulin resistance, despite any maintenance of their traditionally higher activity levels.

These results could help shape more effective strategies for reducing rising and significant obesity rates in such populations.

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  • a researcher fits a wearable gps unit on a hadza man
A researcher fits a wearable GPS unit on a Hazda man.
Herman Pontzer, Hunter College

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