Seventeen-year-old Amanda Munson gained confidence and energy as she lost 40 of her 296 pounds after weight-loss surgery and her diabetes went into remission.

"People have told me I not only look thinner, but I seem to glow — maybe because I'm so much happier," she said. The 5-foot-5 high school senior from nearby Burlington, Ky., hopes to lose 75 to 100 more pounds.

Munson is the first of 200 teenagers who will be enrolled in a five-year, federally funded study on the benefits and risks of bariatric surgery on adolescents.

Surgery has been effective in treating extreme obesity in adults. Researchers want to find out if adults and adolescents who have the surgery have significantly different health problems and whether there is any benefit to having the operation earlier in life.

The researchers are responding to the growing problem of extreme obesity among the young.

"We know bariatric surgery is effective for weight-loss. We just need to carefully document how teenagers respond," said Dr. Thomas Inge, associate professor of pediatrics and surgery at Cincinnati Children's Hospital Medical Center, which is leading the study.

Recent data from the Centers for Disease Control and Prevention suggest that about 2 million U.S. adolescents may be severely obese and have complications of obesity previously seen only in adults.

While adult weight-loss surgery still is more common, an estimated 2,744 youngsters nationwide had the operations from 1996 through 2003, with the pace tripling between 2000 and 2003, according to an earlier study co-written by Inge.

The doctors expect their research will show that severe obesity in teens is associated with medical and psychosocial problems which may be more effectively treated during adolescence than waiting until adulthood.

"What's fascinating is that teenagers already can have a half-dozen complications of obesity that the surgery within months — if not weeks — can remedy," he said Inge, who has been performing the surgery on adolescents for five years.

The National Institute of Diabetes, Digestive and Kidney Disorders provided more than $5 million last year for the study. Texas Children's Hospital in Houston, Children's Hospital of Alabama in Birmingham and the University of Pittsburgh also are collecting data.

Researchers will compare data before and after surgery on health factors that include cholesterol levels, liver function, cardiosvascular risk and markers for diabetes. Those findings will be compared with data from a similar study on adults who have been obese since adolescence but are only now having the surgery.

Participants must already have been scheduled for the surgery and must have compelling obesity-related complications such as Type 2 diabetes, sleep apnea, high blood pressure or other cardiovascular risk factors.

Information also will be collected on psychological and social effects of the surgery on the teenagers. Severe obesity can lead to low self-esteem, less social interaction with peers and depression.

Kerri Green, director of education for the Weller Health Education Center in Easton, Pa., believes studies are needed to find out if young people can understand the physical, psychological and emotional consequences of bariatric surgery, which she said should be done only for compelling medical reasons.

"We see a lot of what we call the 'Extreme Makeover' phenomenon, where kids see surgery as a quick fix that will make up for poor eating habits and a lack of exercise," she said.

Munson's mother, Barbara Farnsworth, said they exhausted all other options before resorting to surgery.

"It breaks your heart to see your child struggling and becoming so depressed and to hear doctors say she won't see 30 if she doesn't lose weight," Farnsworth said. "This is only a tool, but I now see a future for Amanda that just wasn't there before."