The largest, longest study of teen obesity surgery shows huge weight loss and health gains can last at least three years, and many say it's worth the risks.

"I feel awesome. It's like a new life," said Miranda Taylor, a Cincinnati nursing student in the study who had surgery when she was 16 and weighed 265 pounds. She lost more than 100 pounds, along with severe depression, pre-diabetes and an obesity-related hormonal condition.

Although she has since gained about 20 pounds, she's still healthy and has surpassed her initial goal of fitting into size 16 jeans — she wears size 14.

"I knew that this might not get me down to like model-size, which I wasn't concerned about. I just wanted to be able to fit into a healthy size," said Taylor, now 20.

"I feel awesome. It's like a new life."

Many of the 228 teens studied started out about three times heavier than what is considered healthy — almost 330 pounds on average. Their average weight loss was more than 90 pounds and for many, obesity-related health problems that vanished early after surgery remained at bay three years later.

Still, after three years most remained obese — just 5 percent achieved a normal weight. And there were drawbacks: A little over half developed low iron levels, which can lead to anemia, and a few had vitamin deficiencies. About 13 percent required additional operations — most for removal of gallstones related to obesity but some were for bowel obstructions or hernias that may have been surgery-related.

There was one death, although the researchers said it was unrelated to surgery.

Similar results for weight-loss surgery have been shown in adults, but there has been more reluctance to perform the operation on teens because of the risks — and until now, the long-term effects in a large group of young patients have been unknown.

The study authors say the benefits from the most drastic way to fight fat still seem to outweigh the risks. But Mary Evans, who oversees obesity research at the National Institute of Diabetes and Digestive and Kidney Diseases, said the patients need to be tracked even longer "to really know what the effects are." The institute paid for the study, and several more years of follow-up are planned.

The study shows teen surgery can reverse obesity-related complications that can have life-shortening consequences, "and that ultimately is more important than actual pounds lost," said Dr. David Ludwig, an obesity expert at Boston Children's Hospital who had no role in the research.

Ludwig noted that the study lacked a comparison group that didn't have surgery. He said it's likely similar results could be achieved with extremely intensive programs including lifestyle changes, mental health help, nutrition counseling and involving all family members — and without the risks. But such programs are rare and lack the quick-fix appeal of surgery.

Guidelines say surgery should be reserved for extremely heavy teens with obesity-related health problems who have failed at other weight-loss methods.

About 20 percent of U.S. teens are obese, meaning their body-mass index is much higher than their peers. In adults, obesity means a BMI of at least 30. In study patients, it was 53 on average before surgery.

The results were published Friday in the New England Journal of Medicine and presented at the Obesity Society annual meeting in Los Angeles.

The study included teens aged 13 to 19 treated at five centers. Most had gastric bypass surgery — a stomach-stapling procedure that reduces the stomach to a small pouch. Almost a third had a less drastic stomach-reducing operation called sleeve gastrectomy.

"Nineteen out of 20 patients that had diabetes were able to reverse that diabetes."

Among the before and after results:

75 percent had unhealthy blood fat levels including high triglycerides and too little good cholesterol: in two-thirds of them it vanished.

40 percent had elevated blood pressure; it returned to normal in three-quarters.

Almost 20 percent had abnormal kidney function; it disappeared in more than 80 percent.

13 percent had Type 2 diabetes; it disappeared in more than 90 percent.

Lead author Dr. Thomas Inge, who directs an obesity surgery program at Cincinnati Children's Hospital Medical Center, said seeing diabetes and other obesity-related health problems resolved was remarkable and gratifying. The weight loss also was encouraging, Inge said, but he added that it's unlikely patients will lose additional weight.

"Nineteen out of 20 patients that had diabetes were able to reverse that diabetes," Inge said.

Obesity surgery should remain a last resort treatment, Inge said. He said families and doctors need to recognize when children's weights are spiraling out of control before they become dangerously obese.

"We need to be thinking proactively and doing something about this far earlier," he said.