NEW YORK — As the popularity of stomach surgery has skyrocketed among obese adults, a growing number of doctors are asking, “Why not children, too?”

For decades, the number of kids trying weight-loss surgery has been tiny. The operations themselves were risky, with a death rate of about 1 in 50. Children rarely got that fat, and when they did, pediatricians hesitated to put the developing bodies under the knife. Only 350 U.S. kids had such an operation in 2004, according to federal statistics.

But improvements in surgical technique and huge increases in the number of dangerously obese children have begun fueling a change of heart.

A group of four hospitals, led by Cincinnati Children’s Hospital Medical Center, are starting a large-scale study this spring examining how children respond to various types of weight-loss surgery, including the gastric bypass, in which a pouch is stapled off from the rest of the stomach and connected to the small intestine.

Three more hospitals have approval from the Food and Drug Administration to test how teens fare with a procedure called laparoscopic gastric banding, where an elastic collar installed around the stomach limits how much someone can eat.

The FDA has hesitated to approve the gastric band for children, but surgeons at New York University Medical Center reported in the Journal of Pediatric Surgery this month that the device holds promise.

The 53 boys and girls, aged 13 to 17, who participated in NYU’s study shed nearly half their excess weight over 18 months, while suffering relatively minor complications.

Crystal Kasprowicz, of St. James, N.Y., said she lost 100 pounds from her 250-pound frame after having the band installed at age 17.

“I’m a totally different person,” she said.

Before the procedure, Kasprowicz said she took medication for a rapid heartbeat and was showing signs of developing diabetes. Every effort she made to stop getting bigger failed. Dieting didn’t work, she said. Her heart problems made it hard to exercise. Even walking up stairs was a challenge.

Now, she’s off the heart drugs. Her blood-sugar levels are in check. She also feels better about herself.

“I’m very outgoing now,” said Kasprowicz. “I hike a lot ... I go to the beach in the summer now. I’m not as self-conscious when I go shopping for clothing.”

Similar studies are under way at the University of Illinois Medical Center in Chicago and at the Morgan Stanley Children’s Hospital of New York-Presbyterian, which recently opened a weight-loss surgery center for teens. Doctors there expect to conduct about 50 operations this year.

Children are only considered candidates for surgery after they have spent six months trying to lose weight through conventional methods under hospital supervision. But so far, not a single one has slimmed down enough to take surgery off the table, said Dr. Jeffrey Zitsman, associate attending surgeon at Morgan Stanley Children’s Hospital.

“That battle can only be won in a few instances,” he said.

The studies have followed a huge surge in the popularity of obesity surgeries among adults. The American Society for Bariatric Surgery estimates that more than 177,000 Americans had weight-loss surgery last year, up from 47,000 in 2001.

Not everyone is pleased that kids might be next.

“I don’t think altering the human digestive tract is a solution to the problem of excess weight,” said Joanne Ikeda, a nutritionist emeritus­ at the University of California, Berkeley. “It’s one of these quick-fixes that isn’t a fix at all.”

Doctors, she said, still know relatively little about the long-term effects of such operations on the very young.

The federal Agency for Healthcare Research and Quality released a study in July that said four in 10 weight-loss surgery patients develop complications within six months. Among adults, mortality rates among gastric bypass patients remain at between 1 in 100 and 1 in 200 patients.

Laparoscopic gastric banding has been shown to have a much smaller death rate — about 1 in 1000 patients — but complications do occur.

Of the patients who participated in the NYU study, two needed a second operation to adjust a slipping band; two developed hernias; five got an infection; five suffered mild hair loss and four had iron deficiencies related to their new diet. After the study was complete, one patient asked to have her band removed because of discomfort, said Evan Nadler, a pediatric surgeon and co-author of the study.

Nadler said those complications were minor compared to the chronic diabetes and cardiovascular disease teens would face if they remained that heavy into adulthood.

“These are people who have tried everything they could possibly try,” he said, noting that their mean weight at the study’s start was 297 pounds. “Once they reach this level of morbid obesity, the vast majority go on to be obese adults,” he said.

Thomas Wadden, an obesity expert at the University of Pennsylvania School of Medicine, said surgery can be of immense benefit to some teens, especially those already experiencing health problems.

But he also advised caution.

Egged on by TV shows and commercials expounding the benefits of weight-loss surgery, adult patients have begun showing up at Penn’s Center for Weight and Eating Disorders demanding an operation as an easy first step to thinness.

“When we ask them, ’What have you done so far to lose weight?’ The patients say, ’Nothing,”’ Wadden said. “They’re going right to a $25,000 operation for which they are ill-prepared.”

It would be tragic, he said, to see the same phenomenon repeated among children.

“They have to be selected with caution to make sure that this aggressive step is absolutely necessary.”