By ANEMONA HARTOCOLLIS

Though Shani Gofman had been teased for being fat since the fourth grade, she had learned to deal with it.

She was a B student and in the drama club at school. She had good friends and a boyfriend she had met through Facebook. She even showed off her curves in spandex leggings and snug shirts.

When her pediatrician, Dr. Senya Vayner, first mentioned weight-loss surgery, Ms. Gofman was 17, still living with her parents in Bensonhurst, Brooklyn, her bedroom decorated with glow-in-the-dark stars because she was afraid of the dark.

There was no question, at 5-foot-1 and more than 250 pounds, she was overweight. But she resisted, saying she could diet.

“I’ll lose weight,” Ms. Gofman assured her doctor.

Dr. Vayner said, prophetically, “It’s not your fault, but you’re not going to be able to do it.”

Along with the obesity epidemic in America has come an explosion in weight-loss surgery, with about 220,000 operations a year — a sevenfold leap in a decade, according to industry figures — costing more than $6 billion a year. And the newest frontier is young patients like Ms. Gofman, who allowed The New York Times to follow her for a year as she had the operation and then embarked on a quest to lose weight, navigating challenges to her morale, her self-image and her relationships with family members and friends.

But the long-term effectiveness of weight-loss surgery, particularly stomach banding, the procedure Ms. Gofman had, is still in question. And the push toward surgery on the young has brought some resistance from doctors who say it is too drastic to operate on patients whose bodies might still be developing and who have not been given much time to lose pounds on their own.

“I think it’s pretty extreme to change the anatomy of a child when you haven’t even tackled the other elements,” said Dr. Wendy M. Scinta, a family practitioner in Manlius, a suburb of Syracuse, who specializes in pediatric weight loss. Unlike with older patients, she said, “there is not a huge rush to fix it or they will die.”

One percent to 2 percent of all weight-loss, or bariatric, operations are on patients under 21, but studies are under way to gauge the outcomes of surgery on children as young as 12. Allergan, the maker of the popular Lap-Band, a surgically inserted silicone band that constricts the stomach to make the patient feel full quickly, is seeking permission from the Food and Drug Administration to market it to patients as young as 14, four years younger than is now allowed. Hospitals across the country have opened bariatric centers for adolescents in recent years.

Doctors who are open to operating on younger patients note there is substantial evidence that dieting frequently fails.

“Most of us have witnessed the medical establishment provide the same advice over and over again to kids who are overweight — they just need to diet and play more outside,” said Dr. Thomas Inge, a professor of surgery and pediatrics at the University of Cincinnati, who is participating in a National Institutes of Health study of weight-loss surgery on teenagers. “I wish it were that simple.”

25 Minutes, and It’s Done

Ms. Gofman has been overweight for almost as long as she can remember. The boys on the school bus made fun of her. In school pictures, she never wanted to be shown sitting. “I wanted to be standing with people blocking me,” she said.

After her doctor proposed surgery, she tried to lose weight but failed miserably, gaining 30 pounds in eight months. Maybe, she said, she secretly wanted to qualify for “the easy way out.”

In December 2010, Ms. Gofman, who had just turned 19, and her mother arrived at the office of Dr. Danny Sherwinter, the wiry, fast-talking chief of bariatric surgery at Maimonides Medical Center in Brooklyn, for a consultation. Ms. Gofman was nervous but eager.

She had been sold on the Lap-Band, the only operation Dr. Sherwinter performs, because it is reversible and relatively low risk. She weighed in at 271 pounds, with a body mass index of 51, well above the minimum B.M.I. of 40, or 35 for people with at least one other related health problem, that was required for the use of the Lap-Band. (In February, the F.D.A. reduced the minimum B.M.I. for patients with another problem to 30, the threshold of obesity.)

Ms. Gofman’s mother asked what would happen if her daughter wanted to get pregnant. The band would be decompressed, Dr. Sherwinter said, and “basically you’re a normal pregnant woman, eating your pickles and ice cream.”

“Yummy,” Ms. Gofman said.

“What about the skin?” her mother, Judith, asked, meaning loose skin that might develop after weight loss.

“That’s going to be an incredible conversation,” Dr. Sherwinter said. “Let’s just get there first.”

He told Ms. Gofman that, going by the averages, she could expect to lose about 40 percent of her excess weight, or 70 to 80 pounds. “Which is better than any diet out there,” he said. “We’d be looking for you to come in around 200.”

But, he warned, “If you don’t follow along the average way, like have a milk shake every night or don’t exercise at all, you will end up in the worser half.”

Dr. Sherwinter asked her to prepare for surgery by going on a liquid diet. But she privately reasoned, “I’m about to have surgery, so I might as well enjoy myself.”

Ms. Gofman showed up at the hospital at 6 a.m. on Dec. 22, 2010, after staying up with friends the night before, too nervous to sleep. She kept asking the nurses and doctors to reassure her that she would wake up after the surgery. Her parents and her boyfriend, Abie Feldman, were by her side.

A friend sent her a text message: “We’re not fat. We’re professional eaters. Why should we be punished for our profession?” Ms. Gofman laughed.

By 8 a.m., she was under anesthesia. Dr. Sherwinter marked five points in black ink on her stomach, then used a knife to make five tiny slits, the largest about half an inch wide, through the layers of skin and fat.

He distended her abdomen with carbon dioxide so there would be more space to work, and asked for music, soft rock, to be turned on.

The operation was done laparoscopically, using a camera and surgical instruments inserted through the incisions, while Dr. Sherwinter watched on a video screen. He wrapped the band around the neck of Ms. Gofman’s stomach and cinched it with a ridged buckle, like the type on swimming goggles.

Dr. Sherwinter wrapped part of the stomach around the band and stitched it into place, to prevent the band from slipping. On the screen, the white ring, prominently labeled “Allergan,” looked like a spaceship that had landed in alien territory.

The operation took about 25 minutes. Child Health Plus, a state insurance plan for low-income families, covered the $21,369 cost. Medicaid in almost every state and many private health plans now cover bariatric surgery, often more readily than diet or exercise plans.

On many days, Dr. Sherwinter performs three or four operations in a row. “She’s a relatively skinny woman, which makes it easier,” he said of Ms. Gofman, using a jarring description for a woman who was 160 pounds overweight. “When you get to the larger men, it becomes more difficult.”

Long-Term Questions

Ms. Gofman’s procedure, called laparoscopic adjustable gastric banding, constitutes about 39 percent of all bariatric surgeries. The other two main types are Roux-en-Y gastric bypass, which involves stapling the stomach into a tiny pouch and rearranging the bowel, and sleeve gastrectomy, which involves removing most of the stomach and turning what is left into a thin tube.

The risks of all the operations have declined, partly because surgeons are now more experienced and using less-invasive techniques, like laparoscopy, but also because they are beginning to operate on thinner, healthier patients.

One in 2,000 gastric banding patients, or 0.05 percent, and 1 in 900 gastric bypass patients die during or immediately after surgery, according to William Encinosa, a senior economist at the federal Agency for Healthcare Research and Quality who analyzed 161,000 surgical records for 2009. For open — not laparoscopic — bypass surgeries, studies have put the death rate within 30 days as high as 2 percent. About 1 percent of banding patients and 3 percent of bypass patients develop major complications, like blood clots or perforation of the bowel, Dr. Encinosa said.

Allergan, which also makes Botox, so dominates the banding market that Lap-Band is often used as a generic name, like Kleenex or Band-Aid. But its push to win F.D.A. approval to market to younger patients comes amid early evidence that gastric banding may produce poor long-term results.

A Belgian study of adult patients found that nearly half had their bands removed within 12 years for various reasons, according to the study’s principal author, Dr. Jacques Himpens: they did not lose much weight; they regained what they had lost; they had frequent heartburn or vomiting; or the band would slip or perforate the stomach.

A German study found that 30 percent of patients needed new operations within 14 years, some because they wanted bands removed, and others because of complications like slippage.

Another study in Australia found that one-third of operations on teenagers required follow-up surgeries within two years, often because of “pouch dilation,” when the stomach above the band becomes enlarged, which can happen if the patient does not follow the regimen and tries to eat too much.

Cathy Taylor, a spokeswoman for Allergan, noted that the studies involved small sample sizes: the adult ones had fewer than 300 patients combined, and the Australian study, two dozen. Ms. Taylor said that the adult studies did not reflect recent improvements in the band and in surgical techniques, and that the complications in the teenage study were not serious.

Stomach enlargement, she said, “speaks to the importance of additional education for the adolescent to understand the importance of adhering to the new eating program.”

But that, said Diana Zuckerman, a psychologist and president of the National Research Center for Women and Families, goes to the heart of why teenagers are bad candidates for bariatric surgery: they are often immature, rebellious and uninterested in long-term consequences.

“It’s not just you can’t eat Thanksgiving dinner,” Dr. Zuckerman said. “You’re going to have to have this tiny little meal for the rest of your life.”

A more critical question is whether surgery can lead to malnutrition, particularly in bypass patients because their shortened digestive tracts absorb fewer nutrients, which could affect bone growth, sexual maturation and other development.

“Kids across the country are getting this surgery, and we need to know the consequences,” said Dr. Mary Horlick, project scientist for the National Institutes of Health, which is sponsoring a study of bariatric surgery in about 250 teenagers.

Surgeons who operate on teenagers say the alternative is worse: a lifetime of obesity, ostracism and diseases like diabetes. Dr. Jeffrey L. Zitsman, director of the center for adolescent bariatric surgery at NewYork-Presbyterian/Morgan Stanley Children’s Hospital, says that among the biggest obstacles are pediatricians and family doctors, nearly half of whom, according to a recent medical journal article, say they would never refer a teenager for obesity surgery.

But Dr. Zitsman said: “These kids are sick, and they’re going to get sicker. It’s like having a precancerous condition that you can treat rather than waiting till it’s cancer.”

And there are success stories. One of Dr. Inge’s patients, Kelsie Blackwell, had gained weight after getting a cancerous brain tumor that is now in remission. She had bypass surgery at 16, and dropped to 130 pounds from 215. She has maintained that weight for three and a half years. “She became much more social after the surgery,” her mother, Tawana Blackwell, said.

Seeing Results

Ms. Gofman arrived for her first postoperative visit 13 days after the surgery, stylishly dressed in a bias-cut black sweater, blue pants and short snow boots. The scale read 251 pounds, 20 pounds below that of her last weigh-in.

But her mood did not match. “You know how you said I can have mashed potatoes a little bit,” she told Dr. Sherwinter. “I measured it. I didn’t feel full at all. Then I was bad. I ate a little bit more and a little bit more, and I still didn’t feel full, but I stopped.”

Ms. Gofman wanted a “fill” of her band, an infusion of saline to make it even more constricting, even though Dr. Sherwinter had told her to wait six weeks before tightening it. She then confessed that she had also eaten a dumpling skin.

“That’s probably not the best thing to do,” Dr. Sherwinter said. “Dumplings are fried and have mongo calories.”

“I’m just so nervous to fail my own diet,” she said. “There’s a diner downstairs from my apartment, and a Dunkin’ Donuts.”

“The key is moderation, having a little mashed potato but not a portion,” he said.

“I’m not good at moderation,” she replied.

Later, waiting on the elevated subway platform for the train to work, Ms. Gofman brooded about how her surgery had upset the rhythms of the household. “My mother doesn’t cook so much if there is no one to eat it,” she said.

Three weeks later, she was down 8 more pounds, to 243. She had shrunk to size 20 from 26 and had bought several pairs of jeans. She had joined a gym and had bought a swimsuit.

“Friends give me compliments,” she told the physician assistant, Elana Guzman. “I go out more. It’s easier walking upstairs. Exercising is not as hard. I fit into a lot of clothes I didn’t fit into before.”

Ms. Gofman raised her shirt and Ms. Guzman inserted a needle into a port that Dr. Sherwinter had planted in her abdomen. Ms. Guzman squirted three cubic centimeters of saline solution, one-tenth of an ounce, into the band, which holds 10 cubic centimeters.

By June, Ms. Gofman was down to 237 pounds.

Bumps in the Road

Then summer came. Ms. Gofman took a free trip to Israel with other teenagers. She missed her clinic visits, and often ate on the run.

She would wolf down her food, and then she would run to the bathroom to vomit or sit in pain waiting for it to make its way through the band. “I couldn’t even have a single little sandwich without embarrassing myself and going to the bathroom,” she said.

To her dismay, she discovered that “all the fattening foods” — chips, chocolate — went down easily. “Apples and bread are hard,” she said. “It’s annoying how hungry I was.”

Ms. Gofman started to feel judged by some of her friends. “Some will ask a dumb question, like, how’s the surgery going?” she said. She felt like telling them, “You obviously can tell it’s stalled, right?”

By fall, she had canceled her gym membership because it was too expensive. When the hospital urged her to come in for a visit, she said she was busy. But the truth was that she had aged out of the child health insurance program, and she was embarrassed to be gaining weight.

She finally confessed to the hospital that she could not pay. The physician assistant told her they would “work it out.”

Ms. Gofman, who has just turned 20, saw Dr. Sherwinter in November. She had regained not quite half of what she had lost. He did not scold or blame her. He tightened her band, so it now took an hour and a half to force down two scrambled eggs.

She does not want to reveal how much she weighs, but she is fighting constant hunger, and progress is slow.

Her boyfriend consoles her, she said: “I say, ‘I can’t wait till I’m skinny,’ and he says, ‘You’re beautiful the way you are.’ ”