New York ? Obesity surgery can reverse diabetes in teens just as it does in adults, according to a small study.

All but one of the 11 extremely obese teens studied saw their diabetes disappear within a year after weight-loss surgery, the researchers reported. The 11th patient still had diabetes, but needed much less insulin and stopped taking diabetes pills.

Previous studies have shown the diabetes benefits of obesity surgery for adults. Dr. Thomas Inge, a pediatric surgeon at Cincinnati Children’s Hospital Medical Center, and his colleagues wanted to find out whether the same was true for adolescents.

Although more research is needed, Inge said the study “opens the door” to weight-loss surgery as a treatment option for severely obese teens with Type 2 diabetes.

The results are in the January issue of Pediatrics and are being released today.

About a third of U.S. youngsters are either overweight or obese. Increasing numbers of obese children are being diagnosed with Type 2 diabetes, the most common form of the disease and the one linked to obesity. It was seldom seen before in kids.

Teen candidates for weight-loss surgery need to be carefully selected, he said, since the long-term consequences of the operation for children aren’t yet known.

As for the one surgery patient whose diabetes wasn’t reversed, the researchers said the reason wasn’t known, but they noted his mother and a younger sibling also had Type 2 diabetes.

Another explanation could be that his diabetes was more advanced than the other teens’, Inge said. Adult studies have indicated that the chances of diabetes reversal are better the sooner surgery is done after diagnosis, he said.