Losing weight can dramatically reduce your risk of serious diseases, but what really happens to your organs when you put on the pounds? Researchers say finding out why weight gain affects some people's organs differently is an important step to treating obesity.

It's an epidemic of epic proportions. More than 60 percent of people in the United States are considered fat.

"It's abnormal, it's unusual to be lean in this country," said Dr. Samuel Klein, Director of the Center for Human Nutrition at Washington University School of Medicine in St. Louis.

For many, obesity will lead to type 2 diabetes and heart disease, but for 25% of obese people there are no adverse effects. Now researchers are trying to learn why using an unlikely method.

"Kentucky Fried Chicken, Mcdonalds, Taco Bell, Pizza Hut and Burger King: We really are paying people to gain weight there's no question about it," Klein said.

As part of the "overfeeding" study, O.R. nurse Dawn Dreeman agreed to eat an extra one-thousand calories a day, all from fast food.

The goal is to study what happens to the body as people gain weight. Dr. Sam Klein says using fast food is a cheap and easy way to track calories. For Dawn it was the only thing that came easy.

"I couldn't climb stairs after 2 to 3 weeks. I was tired. I couldn't breathe. I gained a total of 20 lbs!" Dreeman said.

"The information we gain from these studies will help us understand why obesity and excess body fat causes metabolic diseases and if we can understand that link better we can develop better therapies to break that link," Klein explained.

After participants gain 5 percent of their body weight, they're put on a 6-month weight-loss program. Five months into her weight loss, Dreeman dropped the pounds and gained a fondness for something else.

"I consciously put vegetables on my plate now. I feel good I have my energy back," she said.

The study is funded by the National Institutes of Health. Participants are paid $3500 for the study and are compensated for the food. Klein says preliminary results show some people really are resistant to having the adverse affects of weight gain. The study is still enrolling for more information on enrollment qualifications, click here.