According to new research that truism is only half right. In a new study analyzing eating and exercise habits over the last few decades, researchers say America's growing obesity problem is mostly the consequence of its increasingly sedentary lifestyle, not its growing calorie count.
In studying data from the National Health and Nutrition Examination Survey, researchers at Stanford University were able to show that, from 1994 to 2010, the number of adult women in the U.S. who admitted to engaging in no physical activity grew from 19.1 to 51.7 percent.
In 1994, just 11.4 percent of men said they mostly abstained from exercise. In 2010, that number had risen to 43.5 percent.
All along the way, America's collective body mass index, or BMI, has steadily increased. And while exercise has become less and less popular over this time period, America's diet has remained largely -- at least as far as calories are concerned -- the same.
"These changes have occurred in the context of substantial increases in the proportion of adults reporting no leisure-time physical activity, but in the absence of any significant population-level changes in average daily caloric intake," reiterated lead investigator Uri Ladabaum.
Ladabaum and her colleagues recently published their findings in the American Journal of Medicine.
"Our findings do not support the popular notion that the increase of obesity in the United States can be attributed primarily to sustained increase over time in the average daily caloric intake of Americans," added Ladabaum.
Of course, none of this means it's okay for men and women to entertain unhealthy eating habits as long as they exercise.
Pamela Powers Hannley -- the managing editor of the American Journal of Medicine -- says that the most reliable solution to America's obesity problem remains the same: improve dietary habits and exercise more.
"If we as a country truly want to take control of our health and our health care costs, the Ladabaum et al paper should be our clarion call," Hannley wrote in an op-ed accompanying the new study. "From encouraging communities to provide safe places for physical activity to ensuring ample supply of healthy food to empowering Americans to take control of their health, we must launch a concerted comprehensive effort to control obesity."