LA CROSSE, Wis. (WKBT) -

It turns out our diets may not be causing more Americans to become obese.

The Stanford University School of Medicine says not getting enough exercise may actually be to blame.

The researchers examined data from the National Health and Nutrition Examination Survey between 1988 and 2010.

They found no evidence that Americans are eating more than they used to. Rather, the percent of Americans not exercising more than doubled in women and nearly quadrupled in men.

"We've gotten away from using manual labor, and now we sit in front of computers for most of the day," said Gundersen Health System weight management consultant Marisa Pruitt. "Most of our activities or fun things we do on the side are sedentary activities -- we drive cars instead of bike -- so all of that has an impact on our waistline."

Pruitt recommends 30 minutes of exercise a day and an increase in daily movement.