NEW YORK - When it comes to weight-loss surgery for very obese adolescents, having the surgery sooner rather than later may yield a better long-term outcome, new study findings hint.

Surgical treatment for extreme obesity may be appropriate for some adolescents, Dr. Thomas H. Inge, of Cincinnati Children's Hospital Medical Center, Ohio, and colleagues note in the Journal of Pediatrics.

Based on their experience, Inge told Reuters Health, "the timing of surgery for adolescent obesity is an important consideration, as 'late' referral for (weight-loss) surgery at higher body mass index (BMI) values may preclude reversal of obesity or extreme obesity within the first post-operative year and may increase the risk of weight regain over the long term."

But regardless of body weight going into the surgery, weight-loss surgery improves cardiovascular risk factors and brings body weight down significantly in all patients, the study team found.

BMI -- calculated by dividing weight in kilograms by height in meters squared -- is a standard way to determine how fat or thin a person is. Values between 20 and 25 are typically considered normal. Any value of 30 or greater is considered obese. Morbidly obese people have a body mass index (BMI) of 40 or greater -- equal to being about 100 pounds or 50 kilograms overweight.

To determine the effect of pre-surgery BMI status on outcomes in their younger patients, Inge's team followed 61 adolescents for a year after they underwent the most common and most effective form of weight-loss surgery for severe obesity called Roux-en-Y gastric bypass.

The procedure involves stapling off the upper portion of the stomach to create a small pouch that restricts the amount of food a person can eat at one time. The surgeon also makes a bypass from the pouch that skirts around the rest of the stomach and a portion of the small intestine, limiting the body's absorption of nutrients.

Inge's team stratified the adolescents in their study into three groups based on their pre-surgery BMI. Group 1 consisted of 23 patients with a BMI between 40.0 and 54.9. Group 2 consisted of 21 individuals with a BMI between 55.0 and 64.9, and Group 3 consisted of 17 individuals whose BMI fell between 65.0 and 95.0.

The average BMI in the overall cohort, which was 60.2 at the time of surgery, fell by roughly 37 percent at 1 year after surgery, with little variation in BMI reduction among the groups, the investigators report.

It is noteworthy, the investigators say, that subjects in Group 1 -- who had the lowest BMI going into the surgery -- had the lowest BMI a year after the surgery. Still, only 10 patients (17 percent) achieved a BMI of less than 30 at 1 year. Eight of these 10 were from Group 1.

"In this investigation, we found that most adolescents within the highest ranges of baseline BMI...remained extremely obese...despite BMI reductions averaging nearly 40 percent," the investigators note.

Adolescents "who present at higher weights and BMI values lose more weight than those who present at lower weights but also plateau at a higher weight on average," they add. "The biological and potentially behavioral reasons for this are unclear."

Regardless of pre-surgery BMI, weight-loss surgery led to a healthy reduction in blood pressure, cholesterol levels and triglycerides (harmful blood fats).