Losing weight is not easy but keeping it off can prove even harder. NIH researchers are studying ways to keep lost weight off in research that blends entertainment and science.

The researchers followed contestants from NBC's televised weight loss competition, "The Biggest Loser." The TV show encourages contestants to lose weight through a strict diet and exercise program.

After losing an average of 132 pounds during the show, many of the 14 former contestants the study followed gained back weight they had lost after six years.

But the amount of weight they kept off varied.

Half maintained an average weight loss of 25 percent of their starting weight. The other half returned to a weight very close to their starting weight.

The main difference between those who maintained significant weight loss and those who did not was their level of physical activity. Both groups had a lower calorie intake than before the show, but the half that maintained significant weight loss was substantially more active.

"Our findings are consistent with other studies in which participants who kept their weight off reported significantly more physical activity than those who regained their weight," said lead researcher Kevin D. Hall, Ph.D.

Excess weight raises your risk of developing serious health problems. Healthy eating and regular physical activity help you lose weight.

To find out more about weight control, visit MedlinePlus.