They say \u201cabs are made in the kitchen\u201d and \u201cyou can\u2019t outrun a bad diet\u201d\u2014and a recent study in the Proceedings of the National Academy of Sciences suggests there\u2019s science to back up those cliches.\n<\/p>\n
Diet\u2014not physical inactivity\u2014seems to be the primary driver of the obesity epidemic, according to the new research.\n<\/p>\n
\u201cThis is not saying that physical activity isn\u2019t important. It absolutely is,\u201d said Amanda McGrosky, PhD<\/a>, an assistant professor of biology at Elon University who co-authored the new study. But if weight loss is your goal, her research suggests the gym may not hold the solution.\n<\/p>\n Both diet and exercise are important to overall health and wellness. But when it comes to weight management, does one matter more than the other?\n<\/p>\n McGrosky and her colleagues set out to answer that question. They compared data on daily calorie burn, body fat percentage, and body mass index (BMI) from more than 4,000 people living across six continents. Some were highly active farmers or hunter-gatherers, while others lived in industrialized nations and were far more sedentary.\n<\/p>\n People in industrialized nations tended to have higher body masses, BMIs, and body fat percentages, they concluded. But after adjusting for body size, the researchers found that they were burning only slightly fewer calories per day than people in less-developed areas\u2014even though their lifestyles were much less active.\n<\/p>\n \u201cWe didn\u2019t see [big] differences in total energy expenditure across populations, but we do see this increase in body fat,\u201d McGrosky told Health. \u201cIf we\u2019re not changing the number of calories out, we have to be changing the number of calories in.\u201d\n<\/p>\n In other words: Obesity may be on the rise in some countries not because people are failing to burn enough calories, but because they are consuming too many.<\/p>\n The study relied on a mix of observation and modeling, meaning it can\u2019t definitively prove cause and effect. Still, outside experts say there\u2019s plenty of other research to back its conclusions.\n<\/p>\n \u201cAlmost everyone that comes to me and wants to talk about their weight begins by talking about their efforts at physical activity,\u201d said Max Petersen, MD, PhD<\/a>, an assistant professor in the Washington University in St. Louis Medicine Division of Endocrinology, Metabolism & Lipid Research, who was not involved in the new study. \u201cAnd yet it is abundantly clear from decades of research that physical activity really makes a minor contribution to our weight.\u201d\n<\/p>\n Not all studies have found that diet drives obesity more than inactivity. One study from 2014 came to the exact opposite conclusion, and other researchers have found that a combined approach\u2014focused on both diet and exercise\u2014is the best system for sustained weight loss.\n<\/p>\n