The criteria for selecting obese adolescents as candidates for bariatric surgery have loosened in recent years, and now that the adolescent field has converged on a roughly uniform body mass index standard that's the same as for adults—at least 35 kg/m
The goal, they agree, is to offer bariatric surgery to patients aged 13-17 years safely but at a stage when the surgery has the best potential to normalize patients' weight so that comorbidities improve and possibly resolve.
An aggressive approach may also help avoid another problem. “No one can explain why, but there is a plateauing effect of all bariatric surgery, be it gastric bypass, gastric sleeve, or gastric banding. Patients lose about 15 BMI [body mass index] points but no more,” said Dr. Evan P. Nadler, director of the bariatric surgery program at Children's National Medical Center in Washington. “The chances of getting patients near a normal body weight once they reach a BMI of 45 or 50 are quite small.”
The reasons behind this limit to the effect of bariatric surgery remain elusive. Many surgeons believe that the adaptable human body kicks in a thermostatlike resetting that maintains a certain body weight starting about a year after the large initial loss following surgery. Another factor may be that many patients have lifestyle regression at some point after surgery.
Regardless of the cause, the apparent limit to weight loss for most patients suggests to pediatric surgeons that bariatric surgery has the greatest potential to normalize BMI, and thereby prevent comorbidities, when applied early, before BMI gets too high and before end-organ damage is irreversible.
“If you get to younger patients, they may still be in a window of opportunity for their end-organ disease to essentially be reversed,” Dr. Marc P. Michalsky said.
“Our hope is that perhaps in adolescents, without decades of cardiac disease, hypertension, and liver disease, once their weight is off you may see more resolution of that disease than in adults. That's the hypothesis, but we haven't proven it yet,” said Dr. Michalsky, surgical director of the center for healthy weight and nutrition at Nationwide Children's Hospital in Columbus, Ohio.
“It's a new concept to think of surgery as preventive medicine, but it is preventive in the sense that patients have more severe comorbidities if you wait,” said Dr. Ai-Xuan Holterman, director of pediatric surgery at Rush University Medical Center in Chicago.
“You could argue that in a 14-year-old who is obese but has no comorbidities, there is no urgency to do surgery. But we know what the natural trajectory of these patients will be. If a patient is older than 14 and morbidly obese, even if their comorbidities are relatively minor, I think that surgery is an appropriate option,” Dr. Nadler said in an interview.
Another benefit of early surgery is that “the risk of operating on a patient at a BMI of 45 is a lot different than operating on someone with a BMI of 60,” he added.
Still, U.S. studies have yet to report outcomes from bariatric surgery in adolescents at more than 3 years of follow-up.
In one analysis of 61 adolescent gastric bypass patients, the average percentage of lost BMI was about 37% across all weight categories, and two-thirds of the variance in BMI 1 year after surgery was attributable to the variance in baseline BMI (J. Pediatr. 2010;156:103-8).
The shift in surgical criteria for adolescents means that most surgeons now follow the same guidelines that have been standard for adult patients for nearly 2 decades. Serious comorbidities that lower the threshold to 35 kg/m
In 2004, a group of surgeons who at the time primarily favored gastric bypass for their adolescent patients published recommendations that called for limiting bariatric surgery for adolescents to those with a BMI of at least 40 kg/m
Last year, a surgeon from that group, Dr. Thomas H. Inge of Cincinnati Children's Hospital, worked with a different group of collaborators to write revised criteria, which set their threshold BMI at 35 or 40 kg/m
Dr. Nadler and his associates published their own endorsement for applying the adult BMI criteria for bariatric surgery to adolescents in another paper that appeared last year (J. Pediatr. Surg. 2009;44:1869-76).
“What is crucial is that you're not operating just because of BMI or weight, but that there is a compelling health indication,” said Dr. Inge, surgical director of the surgical weight loss program for teens at Cincinnati Children's.
He cited preliminary evidence collected by his collaborators that, for example, “the pediatric heart may be more resilient to remodeling” than an adult's heart, and more likely to return to normal following significant weight loss. “There may be a window of opportunity to act before there is more permanent damage to the heart,” he said in an interview.