“Don’t get diabetes in the first place,” said Dr. Phil Zeitler of the University of Colorado Denver, one of the study leaders.

A third of American children and teens are overweight or obese. They are at higher risk of developing Type 2 diabetes, in which the body can’t make enough insulin or use what it does make to process sugar from food. Until the obesity epidemic, doctors rarely saw children with Type 2 diabetes. The more common kind of diabetes in children is Type 1, which used to be called juvenile diabetes.

Doctors usually start Type 2 treatment with metformin, a pill to lower blood sugar. If it still can’t be controlled, other drugs and daily insulin shots may be needed. The longer blood sugar runs rampant, the greater the risk of suffering vision loss, nerve damage, kidney failure, limb amputation — even heart attacks and strokes.

The goal of the study was simple: What’s the best way for teens to keep diabetes in check?

The study involved 699 overweight and obese teens recently diagnosed with diabetes. All had their blood sugar normalized with metformin, then were given one of three treatments to try to maintain that control: metformin alone, metformin plus diet and exercise counseling, or metformin plus a second drug, Avandia.

After nearly four years, half in the metformin group failed to maintain blood sugar control. The odds were a little better for the group that took two drugs but not much different for those in the lifestyle group.

Even so, Zeitler said doctors would not recommend this combination drug therapy because Avandia has been linked to higher risk of heart attacks in adults. Those risks became known after this study had started.

Another study leader from Children’s Hospital Los Angeles, Dr. Mitchell Geffner, agreed that Avandia can’t be recommended for teens, but said the study makes clear they will need more than metformin to control their disease.

“A single pill or single approach is not going to get the job done,” he said.

Among all the teens in the study, 1 in 5 had a serious complication such as very high blood sugar, usually landing them in the hospital.

The results were published online Sunday by the New England Journal of Medicine and presented at a pediatric meeting in Boston. The National Institutes of Health funded the study and drug companies donated the medications.

The “discouraging” results point to the need to create “a healthier ‘eat less, move more’” culture to help avoid obesity that contributes to diabetes, Dr. David Allen of the University of Wisconsin School of Medicine and Public Health wrote in an accompanying editorial.