There’s an old saying: You are what you eat. But here’s some food for thought on that: a new study suggests that lack of exercise, not how many calories you eat
may be the main factor in America’s obesity epidemic, especially among young women.

The study published in the American Journal of Medicine analyzed data from the National Health and Nutrition Examination Survey (NHANES) from the last 20 years. It found a sharp decrease in physical exercise and an increase in average body mass index (BMI), while caloric intake remained the same.

"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," wrote Uri Ladabaum, M.D., the study’s lead author and an associate professor at Stanford University School of Medicine.

Researchers discovered that from 1994-2010, the number of adult women who reported no physical activity jumped from 19.1% to 51.7% in 2010. For men, the number increased from 11.4% to 43.5% in 2010.  At the same time, the average BMI increased across the board; the most dramatic rise among young women ages 18-39.

 

“At the population level, we found a significant association between the level of leisure-time physical activity, but not daily caloric intake, and the increases in both BMI and waist circumference,” said Ladabaum. 

 
The study did not examine what types of foods were consumed, but did observe that total daily calorie, fat, carbohydrate, and protein consumption have not changed significantly over the last 20 years, yet the obesity rate among Americans continues to rise.

Although the study found no association between increased caloric intake and rising obesity rates, this is not a license to raid the refrigerator. If anything, it is a call to get off the couch and start moving.