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Being a couch potato has long been blamed for obesity - a new study has found the real cause
A new study has turned common conceptions of what causes obesity on its head, revealing that reduced physical activity may not have as large a role in our size as our diets.
The study, published this week in PNAS, challenged common wisdom that people in developed nations such as the U.S. are relatively sedentary and burn fewer calories than people in less industrialized countries. Instead, it found that people living in developed nations burned the same amount of calories as people living in less-developed regions, such as farmers, herders and hunters and gatherers, who have much more active lifestyles.
The report, which looked at energy expenditure and metabolic rates of more than 4,000 men and women from a variety of nations, suggests that inactivity is not the main cause of obesity both in the U.S. and elsewhere.
The groundbreaking research found that what people eat 'plays a far greater role than reduced expenditure in the elevated prevalence of obesity associated with economic development.'
Herman Pontzer, a professor and senior author of the study, told the Washington Post that the report's findings are important because they help health officials better know what causes obesity, leading to more successful treatments for patients.
Pontzer and his 80-plus co-authors gathered data from labs around the world that use doubly labeled water in metabolism studies, which allows researchers to exactly determine how someone expends energy.
The researchers calculated total energy expenditures for 4,213 men and women from 34 countries or cultural groups, and found they were similar, regardless of whether someone was an American office worker or a hunter-gatherer.
Regardless of where they lived or how they spent their time, all the people spent similar amounts of energy and burned nearly the same amount of calories each day, the study found.
Instead of finding that increased exercise will decrease obesity, the study suggests that 'increased energy intake has been roughly 10 times more important than declining total energy expenditure in driving the modern obesity crisis,' the authors wrote.
Meaning, populations with greater rates of obesity are simply eating too much – and likely eating the wrong kinds of foods, Pontzer explained.
'This study confirms what I've been saying, which is that diet is the key culprit in our current [obesity] epidemic,' Barry Popkin, a professor at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill and an obesity expert, told the Post.
'This is a well-done study,' he added, to which other experts agreed.
'It's clear from this important new research and other studies that changes to our food, not our activity, are the dominant drivers of obesity,' Dariush Mozaffarian, the director of the Food is Medicine Institute at Tufts University in Boston, said.
Pontzer, a co-author of the study, emphasized that the study's findings do not mean exercise is unimportant to our overall health.
'We know that exercise is essential for health. This study doesn't change that,' Pontzer said.
The study, however, does suggest that to combat obesity, 'public health efforts need to focus on diet,' specifically ultra-processed foods, Pontzer said.
