Experts now say the procedure is the most effective treatment for severe childhood obesity, which affects a growing number of kids. But stigma and insurers often stand in the way.

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For teens struggling with severe obesity, getting that weight off and keeping it off can seem impossible. But experts and the American Academy of Pediatrics say there is an effective treatment for severe obesity in adolescents, bariatric surgery. One in five adolescents suffer with extreme weight problems. Yet only a tiny fraction of them get the surgery. NPR's Yuki Noguchi has more.

YUKI NOGUCHI, BYLINE: As a child, Kayla Northam's body became a battleground. At home, she and her mother fought daily over what she should eat and how much.

KAYLA NORTHAM: Both of my parents have always struggled with their weight. My brother has struggled with his weight. It's a huge family issue.

NOGUCHI: At school, where she dreaded the gym class weigh-in...

NORTHAM: I already knew to be ashamed of the fact that I weighed so much more than everyone else.

NOGUCHI: And in a doctor's office...

NORTHAM: He'd be telling us, you got to get her to diet. And this is back when I'm 5, 6 years old. But I was just always hungry. It was just never enough.

NOGUCHI: As a teen, Northam topped 300 pounds and started developing diabetes and liver and joint problems. Then she heard about something called bariatric surgery. But she knew her mother would never support it.

NORTHAM: In her mind, it's a cheap attempt to lose weight. You know, you could do this if you just worked harder. It's a waste of time because you won't change your habits.

NOGUCHI: So Northam bided her time. Right as she turned 18 and legally an adult, she secretly met with Fatima Cody Stanford, an obesity expert at Harvard.

FATIMA CODY STANFORD: I remember it very clearly. It was, like, the day or so after her birthday, like, as soon as she could get in.

NOGUCHI: That day, Stanford explained how obesity is widely misunderstood.

STANFORD: Obesity is a disease of the brain. And people don't recognize that. They think it's a disease of willpower.

NOGUCHI: Bariatric surgery works, she told Northam, by removing or bypassing much of the stomach where hunger-stimulating hormones are produced. Reducing those hormones alters how the brain signals hunger. Stanford says every person's brain tries to maintain the body at a certain weight or set point. Genetics and lifestyle can alter where the brain sets its target. But when you're struggling with obesity, that target is stuck at a high level and very difficult to lower. But surgery can retrain the brain to find a lower set point.

STANFORD: Bariatric surgery is the best treatment that we have anywhere in the world for severe obesity. It drastically changes set point in a way that nothing else does.

NOGUCHI: Hearing this gave Northam hope.

NORTHAM: I jumped onto her like a life raft. I had so much hope after meeting with her.

NOGUCHI: Bariatric surgery for adolescent patients was rare until about two decades ago. Now more doctors argue broader access to the treatment is necessary, especially as increasing numbers of young people suffer from severe obesity. The surgery, they say, is proving far more effective than medication or diet and exercise alone. There are risks, like vitamin deficiency or regaining the weight. But obesity experts say those are dwarfed by the potentially life-saving benefits. Marc Michalsky is a pediatric surgeon at Nationwide Children's Hospital at Ohio State. He's also a researcher in a multi-year National Institutes of Health study tracking young bariatric patients. His typical patient is 15 or 16 and about 100 pounds overweight. In a large majority of cases, they have related health problems.

MARC MICHALSKY: We're now seeing data that shows that there may be a protective effect of youth. Adolescents undergoing these operations are actually having a more robust improvement in things like diabetes and hypertension.

NOGUCHI: Sometimes within days of getting the procedure.

MICHALSKY: You're talking potentially about a lifetime of that patient not suffering from the cumulative impact of having those diseases had nothing been done in the first place.

NOGUCHI: Basically, it works better than any other treatment to date. Yet it isn't offered to the vast majority of patients who might benefit. That's especially true among people of color, who suffer higher rates of obesity but are less likely to be referred to treatment. Then there is also the issue of cost. Health insurers deny about half of teens' initial request to approve the $20,000 surgery, though, some state Medicaid programs sometimes will. And Fatima Stanford, the Harvard obesity doctor, says parents often think surgery to treat obesity is too extreme.

STANFORD: They're willing to send their kid to surgery to get their tonsils out, to do anything else. But when you start talking about obesity, which is causing, often, a lot of their other medical issues, there is significant resistance.

NOGUCHI: So it was for Kayla Northam, who kept her mother in the dark until just before the surgery. By then, Northam's life had become one lived on the sidelines.

NORTHAM: I've loved playing sports my whole life. I just physically couldn't keep up with my peers. And I wanted to date. Oh, my God. I was boy crazy. There was nothing I wanted more. But none of the boys wanted anything to do with me.

NOGUCHI: She was desperate for a fresh start. But surgery wasn't a quick fix. It required undergoing psychological and medical evaluations and a year and a half of nutrition classes to master an entirely new lifestyle. That was more rigorous because of her youth. Finally, she got the green light. And the effects were immediate. Within days, she lost 25 pounds.

NORTHAM: I thought my scale was broken.

NOGUCHI: She no longer felt prisoner to hunger.

NORTHAM: I was like, oh, my God. This is what normal people feel like when they eat too much. This is my body telling me and me learning, OK, this is all I need.

NOGUCHI: In all, Northam, who is now 28, lost 150 pounds. Men flocked to her

NORTHAM: I, all of a sudden, was having people offer to buy me drinks. Luckily, I would always go out with friends who would be like, Kayla, no, no, no. You don't accept that. So in some ways, my friends had to teach me these things.

NOGUCHI: This is not uncommon, says Thomas Inge, another pioneer in the field. Inge is director of adolescent bariatric surgery at Children's Hospital of Colorado. Inge says as patients lose weight, they're often more social. And with that can come newfound exposure to drugs, alcohol and sexually transmitted disease.

THOMAS INGE: Suddenly, over the course of a very short period of time, they see these risks that they're not at all prepared for.

NOGUCHI: But again, he says, the overall mental health benefits heavily favor surgery. Kayla Northam agrees. She wishes more families would embrace bariatric surgery.

NORTHAM: Because you have kids like I was struggling with depression, not being the person they want to be, not reaching their fullest potential.

NOGUCHI: Northam's says she feels it helped her reach hers. She now works as a gastrointestinal nurse, helping others like her. Yuki Noguchi, NPR News.

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