If all goes well, Aliayha Carrasco-Garcia will have an operation next month that will change her life. She will shed many of the 240 pounds that now burden her 5-foot-2 frame. Like many who have bariatric surgery, she has tried diets and exercise to no avail. Surgery is her last best hope.

But there is a difference between Aliayha and almost everyone else who has had this operation: She is only 15.

While the number of adolescents who are overweight or obese has leveled off in recent years, the number who are severely obese — heavy enough to qualify for bariatric surgery — has nearly doubled from 1999 to 2014, according to national data, going from 5.2 to 10.2 percent of all adolescents aged 12 to 19. As a result, more and more doctors and parents are facing a difficult question: Should very heavy teenagers have bariatric surgery, a radical operation that is the only treatment proved to produce lasting weight loss in severely obese people?

The very idea fills many parents and doctors with trepidation, and with good reason, said Aaron Kelly, a physiologist and specialist in pediatric obesity at the University of Minnesota. “We’re at a point in this field where surgery is the only thing that works for these kids but we don’t know the long term outcomes.”

The best data are from two recently published small studies that so far have outcomes for just five years. Scientists say there’s an urgent need for more ambitious research.

The question for teens and their parents is: Which is worse — accepting uncertainty about the long term health risks from surgery or the likelihood of serious health risks from remaining obese?

An estimated three to four million adolescents are heavy enough to meet the criteria for bariatric surgery, Dr. Kelly said. But only about 1,000 teenagers a year have the operation. Many medical centers will not perform it on teenagers and many pediatricians never mention it to their heavy patients.

“It obviously is a controversial area,” said Dr. Marc P. Michalsky, the surgical director at the Center for Healthy Weight & Nutrition at Nationwide Children’s Hospital in Columbus, Ohio..

Obesity carries serious health risks in teenagers — including type 2 diabetes, high blood pressure, sleep apnea, acid reflux, fatty liver and high cholesterol levels — that tend to be eased by surgery. Added to that are social problems, including isolation and depression.

Yet insurers routinely turn down teenagers on the first request, doctors say, leaving surgeons to appeal, sometimes multiple times, before they can operate on an adolescent. Dr. Kirk W. Reichard, the clinical director of pediatric surgery at the Nemours Alfred I. duPont Hospital for Children where Aliayha is planning to undergo her operation, said Delaware’s Medicaid program had denied coverage for all patients under the age of 18 with one exception.

When it comes to adult bariatric surgery, doctors say, insurers usually do not put up a fight. But doctors and patients often discount the option.

“We still struggle with acceptance in the adult population,” said Dr. John M. Morton, the chief of bariatric and minimally invasive surgery at Stanford. “Acceptance in the pediatric community is even worse.”

The two recently published studies on outcomes were encouraging, obesity experts say. One, involving 58 adolescents, was led by investigators at Children’s Hospital Medical Center in Cincinnati. The other, led by researchers at the University of Gothenburg in Sweden, involved 81 adolescents. Most of the participants in both studies lost at least a third of their weight and kept it off for at least five years. Diabetes often went into remission. Blood pressure readings that were high often fell to normal levels.

Despite their weight loss, 63 percent of the teenagers were still severely obese after the surgery — only one reached a normal weight — and nearly half had nutritional abnormalities, including iron deficiency anemia and low levels of vitamin D and vitamin B12. Nearly half had hyperparathyroidism, a serious condition that leads to the leaching of calcium from bone.

Many more could have reached a normal weight, said Dr. Thomas Inge, the director of adolescent metabolic and bariatric surgery at Children’s Hospital Colorado in Aurora, who led the Cincinnati study, if they had had the operation when they were younger, before they got so obese. The participants’ average age was 17 and their average body mass index was 58.5. (That corresponds to person 5 feet 4 inches tall who weighs 341 pounds.)

Some researchers worry that five years may not be long enough to understand the effect of the surgery on people who undergo it as an adolescent.

The operations alter brain signals that control weight and appetite and change hundreds of nerve and hormonal signals to the brain. What, researchers ask, are the consequences for still-developing brains and bones and bodies? Could low levels of vitamin D cause osteoporosis?

The procedure for teenagers is the same as for adults — either a sleeve gastrectomy, in which much of the stomach is cut away to form a small pouch, or a gastric bypass in which the stomach is made smaller and part of the small intestine is rerouted. The operations are just as safe in teenagers as in adults, surgeons say: Mortality rates are around 0.1 percent, which makes them safer than gallbladder surgery or joint replacement.

Both operations require patients to follow detailed medical instructions, including taking supplements for the rest of their lives after surgery. Adolescents, though, are not always the most compliant patients. Dr. Inge said that when he first started offering the surgery in 2004, several of his patients developed beriberi, a serious condition that can affect the heart and nervous system. It is caused by a lack of thiamine.

You can read the other half of this article on the New Your Times here: http://nyti.ms/2lYT31X