But Dr. Phillip Schauer, current president of the American Society for Bariatric Surgery, said current data on gastric bypass surgery suggest that, for these procedures at least, malnutrition may not pose a huge risk.
"What we've learned is that in general, the nutritional risk from gastric bypass is pretty low," said Schauer, adding that supplements can often help make up for nutrition deficiencies caused by the procedure.
Dr. Neil Hutcher, bariatric and general surgery faculty member at Medical College of Virginia, agreed, adding that growth and development have hardly been an issue in his patients.
"We know that female adolescents have achieved most of their sexual and growth maturity by age 14, and in males it's 15 to 16," he said.
Despite this, some pediatricians remain cautious.
"Bariatric surgery should be a last resort," said Dr. Chuck Wilson, a clinical professor of pediatrics at East Carolina University. "When a complication occurs, it is for the lifetime of the child."
Kopp was not too concerned about any longer-term complications because she ultimately chose laparascopic gastric banding, a reversible procedure in which a band is placed around the entrance to the stomach.
"If there were any complications it could just come out," she said.
Indeed, many physicians are only recommending gastric bands for obese teens seeking surgery.
"We only offer the gastric band due to the significant safety as compared to gastric bypass, both surgical and nutritional," said Dr. Christine Ren, a bariatric surgeon at New York University.
But Schauer notes that while the band is attractive due to its lower risk and reversibility, it does not lead to as much weight loss as gastric bypass procedures, which are riskier and less reversible.
"One has to balance the reduced risk of the band compared to the enhanced weight loss with gastric bypass," he said.
Kopp lost nearly half her body weight with the gastric band. At 5 feet 10 inches, she now weighs 150 pounds -- and she has had no complications since her surgery four years ago.
"It changed everything around," she said. "Everything is good now. I'm dating. I'm going to college next year. I'm more self-confident, and I'm a happier person altogether."
But doctors warn that while surgery worked for Kopp, it's not for every teenager, even if the new study shows low complication rates.
"I think it's important that surgery is not for every teenager, certainly not for teens with a small amount of weight to lose," said Schauer. "For teens suffering from severe obesity who have failed other weight-loss methods, surgery can be very effective and help them restore themselves to good health."
Madelyn Fernstrom, founder and director of the University of Pittsburgh Medical Center weight management center, agreed. She added that teens and parents who are thinking about surgery should choose a center carefully.
"I believe that only centers that provide comprehensive preoperative and postoperative support should be doing these operations," she said. "Nutritional, exercise, behavioral, and medical issues all need to be part of this treatment."