By Mike Pomranz
Updated October 05, 2015
© David Cooper / Getty Images

Americans are getting fatter. That statement is a common refrain as our country continues to battle an obesity epidemic. But new research suggests the problem is not as simple as eating less and exercising more.

A study from York University in Toronto suggests that people today “have to eat even less and exercise more … to prevent gaining weight” than they did just a generation or two ago. According to Professor Jennifer Kuk, her team’s research “indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise.”

Researchers looked at dietary data from almost 36,400 American adults collected between 1971 and 2008. From 1988 to 2006, that data also included stats on physical activity frequency for 14,419 of those participants. When comparing adults with similar food intake levels and similar physical activity levels, they found that despite little difference in these factors, modern adults still weighed more than those from the ’70s and ’80s.

“We observe that for a given amount of self-reported food intake, people will be about 10 percent heavier in 2008 than in 1971, and about five per cent heavier for a given amount of physical activity level in 1988 than 2006,” said lead researcher Ruth Brown. “These secular changes may, in part, explain why we have seen the dramatic rise in obesity.”

So what’s behind the differences? Kuk says the factors behind body weight are more complex than we might realize. She provided a laundry list of possible factors beyond eating and exercise medication use, environmental pollutants, genetics, timing of food intake, stress, gut bacteria and even nighttime light exposure.

Not mentioned was the love of chain-smoking through cocaine-fueled disco parties that dominated the 1970s. That might have kept a few pounds off as well.