CHICAGO (Reuters) - Severely obese teens who had surgery to limit what they could eat lost more weight and enjoyed more health benefits than those who did an intensive lifestyle program, researchers said on Tuesday.

They said 21 of 25 severely obese teens aged 14 to 18 who underwent a form of gastric banding lost more than half of their excess weight compared with just 3 out of 25 who did a diet, exercise and behavior modification program.

"In this study, gastric banding proved to be an effective intervention leading to a substantial and durable reduction in obesity and to better health," Dr. Paul O'Brien of Monash University in Melbourne, Australia, and colleagues wrote in the Journal of the American Medical Association.

O'Brien and colleagues evaluated the effectiveness of Allergan Inc's Lap-Band gastric banding treatment. The procedure involves wrapping an adjustable band around the top of the stomach, giving the patient the illusion of fullness with small meals.

Obesity, which affects nearly a third of U.S. children, has become a top White House priority with the announcement on Tuesday of President Barack Obama's plan to solve childhood obesity within a generation.

Many studies have looked at the safety and effectiveness of weight-loss surgery, or bariatric surgery, in obese adults, but there is less evidence of its safety and effectiveness in children and teens. Gastric banding is a type of bariatric surgery.

The surgery is becoming increasingly popular as obese people struggle to lose weight and avoid the health complications that accompany the extra pounds -- such as diabetes, heart disease, joint pain and some cancers.

Teens in the O'Brien team's study had a body mass index of more than 35 and were assigned to either get the surgery or do a weight loss program. The team followed their progress for two years.

BMI is equal to weight in kilograms divided by height in meters squared. A person 5 feet 5 inches tall with a BMI of 40 would weigh more than 240 pounds (109 kg).

After two years, those in the gastric banding group had lost an average of 28.3 percent of total body weight and 78.8 percent excess weight.

Those in the lifestyle group lost an average 3.1 percent of their total weight and 13.2 percent of their excess weight.

Surgery also helped eliminate metabolic syndrome, a group of related disorders such as obesity, high cholesterol, high blood pressure and abnormal blood glucose.

At the start of the study, 36 percent of those in the gastric banding group and 40 percent in the lifestyle group had metabolic syndrome. After two years, none of the gastric banding patients had metabolic syndrome compared with 22 percent of those in the lifestyle group.

Dr. Edward Livingston of the University of Texas Southwestern Medical Center in Dallas and a contributing editor to the journal, said the results offer more concrete evidence on the use of bariatric surgery as a treatment for obesity in young people.

"The quality of evidence in support of bariatric surgery is poor, resulting in substantial controversy regarding its use for obesity treatment," Livingston wrote in a commentary.

"Many insurance companies in the United States will not pay for bariatric surgeries, and their decision to not cover this treatment is based on the lack of compelling, universally accepted evidence in its favor," he wrote.

They said 21 of 25 severely obese teens aged 14 to 18 who underwent a form of gastric banding lost more than half of their excess weight compared with just 3 out of 25 who did a diet, exercise and behavior modification program.

"In this study, gastric banding proved to be an effective intervention leading to a substantial and durable reduction in obesity and to better health," Dr. Paul O'Brien of Monash University in Melbourne, Australia, and colleagues wrote in the Journal of the American Medical Association.