Baseline BMI is a Strong Predictor of Nadir BMI after Adolescent Gastric Bypass

Objective

Surgical treatment of extreme obesity may be appropriate for some adolescents. We hypothesized that surgical weight loss outcomes may differ by preoperative level of extreme obesity (body mass index [BMI] ≥99th percentile).

Study design

A longitudinal assessment of clinical characteristics from 61 adolescents who underwent laparoscopic Roux-en-Y gastric bypass at a single pediatric center from 2002 until 2007 was performed. Patients were categorized into 1 of 3 preoperative BMI groups: group 1, BMI = 40.0 to 54.9 (n = 23); group 2, BMI = 55.0 to 64.9 (n = 21); group 3, BMI = 65.0 to 95.0 (n = 17). Changes in BMI and cardiovascular risk factors between baseline and year 1 were evaluated using repeated-measures mixed linear modeling.

Results

BMI in the overall cohort at baseline (60.2 ± 11 kg/m²) decreased by 37.4% at 1 year after surgery (P < .001). Percent BMI change varied little by preoperative BMI groups (−37.2%, −36.8%, and −37.7% for groups 1, 2, and 3 respectively; P = .8762). The rate of change in absolute BMI units significantly varied by preoperative BMI class (group × time interaction, P < .0001), with 1-year nadir BMI values for groups 1, 2, and 3 falling to 31 ± 4 kg/m², 38 ± 5 kg/m², and 47 ± 9 kg/m², respectively. One year after surgery, only 17% of patients achieved a nonobese BMI (<30 kg/m²). Significant improvements in systolic and diastolic blood pressure (P < .0001), fasting insulin (P < .0001), total cholesterol (P = .0007), and triglyceride levels (P < .0001) were seen after surgery irrespective of baseline BMI class. Mean albumin levels remained normal despite significant caloric restriction and weight loss.

Conclusions

Laparoscopic gastric bypass resulted in improvement or reversal of cardiovascular risk factors and resulted in a decrease in BMI of approximately 37% in all patients, regardless of starting BMI, 1 year after surgery. The timing of surgery for adolescent extreme obesity is an important consideration, because “late” referral for bariatric surgery at the highest of BMI values may preclude reversal of obesity.

BMI, Body mass index, CCHMC, Cincinnati Children's Hospital Medical Center, DBP, Diastolic blood pressure, FABS, Follow-up of Adolescent Bariatric Surgery, RYGB, Roux-en-Y gastric bypass, SBP, Systolic blood pressure