A study recently published in the Journal of the American Medical Association has found that diet and exercise are effective in helping severely obese people lose weight.

"These severely obese people can respond to, what's considered really, a traditional diet and exercise program to lose a significant and meaningful amount of weight,” said Dr. Bret H. Goodpaster with the University of Pittsburgh School of Medicine.

Researchers looked at 130 severely obese adults for a year. Half followed a diet and exercise plan in a behavioral lifestyle intervention, while the other half received the diet plan but did not start exercising until six months into the yearlong study.

Results show that the group that was physically active during the entire study lost 27 pounds. The group that only got physical activity only in the second six months lost 23 pounds.

"These severely obese people also have meaningful changes in their blood pressure, their insulin resistance, which has been shown to be strongly associated to diabetes risk,” Goodpaster said. “They lose waist circumference, so they lose belly fat in addition to their overall weight loss."

Researchers focused on the severely obese because it is a population that hasn't really been examined in previous weight-loss studies.