Not mom’s weight loss: For millennials, more than diet and exercise at play

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A new study suggests that people have become more prone to weight gain in the last several decades

With the same calories and exercise, a person in 2006 would have BMI higher than someone in 1988

CNN  — 

It’s a never-ending battle: You diet and exercise, but can’t shed the pounds. You can at least take comfort in a new study that suggests many other factors, including stress and pollution, could be conspiring to make weight loss harder today than a few decades ago.

Researchers looked over the years at what adults in the United States said they ate, how much they reported exercising and their body mass index (BMI). The data came from the National Health and Nutritional Examination Survey and included dietary information from nearly 36,400 people between 1971 and 2008, and physical activity information for about 14,400 people between 1988 and 2006.

The study concluded that a person in 2006 who consumed the same number of calories and exercised the same amount as someone in 1988, would have a BMI that was 2.3 points higher. (A BMI of 18.5 to 24.9 is considered normal weight, 25 to 29.9 is overweight and 30 or greater is obese.)

“I didn’t expect to see this finding,” said Jennifer L. Kuk, associate professor of kinesiology and health science at York University in Toronto, who led the research. Obesity rates worldwide have been climbing since the 1980s, and people have always thought it was because we are eating more and exercising less, Kuk said.

But what is to blame, if weight gain is not simply the result of consuming more calories and burning fewer? Although the study did not investigate possible culprits, the authors point to