A new study from the National Institute of Diabetes and Digestive and Kidney Diseases looks at why maintaining weight loss in the long term is such an elusive goal for so many Americans, and what those who are successful at it are doing differently. Not surprising to us is the role that physical activity plays in keeping the weight off.

The New York Times summarizes the study’s findings on the importance of regular exercise

If a man weighing 220 pounds ran an additional 12.5 miles a week at a moderate pace, he would lose more weight, and slightly faster, than if he cut the equivalent amount of calories from his diet, the authors calculated.

However, as activity and calorie reduction are increased, there comes a point at which the weight-loss benefit of diet exceeds that of physical activity, said the researchers, “because the energy expenditure of added physical activity is proportional to body weight itself.”

In other words, heavier people burn more calories in an equivalent amount of exercise; but as their weight drops, the number of calories used in exercise does, too.

The researchers go on to say that despite the drop in calorie burn over time, physical activity is crucial for both weight loss and especially for weight maintenance. Furthermore, the study’s analysis of data from the National Weight Control Registry found that people who successfully lost a substantial percentage of their body weight relied on two methods for maintenance: “continuing physical activity and regular checks on body weight.”

In other words, diet alone is not enough to keep the weight off for good. Unfortunately, when it comes to battling childhood obesity, physical education remains on state budget chopping blocks while food-focused legislation continues to tempt lawmakers. If this study has uncovered the real key to weight control, shouldn’t it be the other way around?