MON-249 Higher Physical Activity Level is Associated with Skeletal Muscle Mass Preservation after Bariatric Surgery in Adolescents with Obesity

Abstract Disclosure: S.B. Zakashansky: None. V.H. Jonokuchi: None. A.F. Zhao: None. J.C. Han: None. Background: Reduction of skeletal muscle mass (SMM) is commonly observed after bariatric surgery in both adults and adolescents. This unfavorable effect on body composition attenuates the benefits of weight loss for metabolic outcomes. Resistance training in adults has been shown to preserve muscle mass during periods of rapid weight loss. Our objective was to examine the association of physical activity and preservation of muscle mass in adolescents undergoing bariatric surgery. Methods: Nineteen adolescents (age 13-20y, mean ± SD: 17.4 ± 1.7y, 68% female, 53% Hispanic White, 37% Black, 10% Non-Hispanic white) enrolled in a multidisciplinary pediatric obesity clinic were assessed preoperatively (before initiation of liquid diet) and at ∼6 months (159 ± 57 days) after laparoscopic vertical sleeve gastrectomy. Nutrition and exercise counseling were provided at monthly visits for at least 6 months before surgery and at each postoperative visit (2 weeks, then every 3 months). Body composition was measured using bioelectrical impedance analysis (InBody 770). Physical activity level (PAL) was assessed using patient-reported Physical Activity Questionnaire-Adolescent. Normality assessments, paired and independent samples T-tests, Pearson correlations, and ANCOVAs were performed. Results: Postoperative reductions in weight (mean ± SEM: -26.0 ± 2.49 kg), BMI (-9.5 ± 0.9 kg/m2), BMIp95 (-28 ± 5%), SMM (-5.2 ± 0.5 kg), percent body fat (-6.4 ± 1.1%), and visceral fat area (-50.4 ± 10.9 cm2) were observed for all patients (p’s<0.001) and there were no significant differences by sex or race/ethnicity. Higher postoperative PAL was associated with lower percentage reduction in SMM (p=0.04, r=0.49). This association remained significant (p=0.04) after adjusting for age, sex, race/ethnicity, baseline BMIp95, and days since surgery. Conclusions: Promoting physical activity may be beneficial for preserving SMM in adolescents undergoing bariatric surgery. Further investigations are needed to determine strategies for encouraging PAL and assessing the contributions of cardiovascular fitness and resistance training in improving metabolic outcomes. Presentation: Monday, July 14, 2025