Metabolic Adaptation and Its Determinants in Adolescents Two Years After Sleeve Gastrectomy

<b>Background/Objective:</b> Weight loss is associated with reductions in resting energy expenditure (REE), which are impacted by changes in body composition following sleeve gastrectomy (SG). Current data regarding changes in measured REE (mREE) and metabolic adaptation in adolescents after SG are limited. We evaluated changes in mREE, metabolic adaptation, and body composition in youths after SG vs. non-surgical (NS) controls over two years. <b>Methods:</b> Youths 14-22 years old undergoing SG (<i>n</i> = 24) and NS controls with severe obesity (<i>n</i> = 28) were recruited. mREE was determined using indirect calorimetry. Predicted REE (pREE) was calculated using regression equation derived from baseline data of our cohort and used to calculate pREE at follow up. Metabolic adaptation was calculated as mREE - pREE. We normalized REE to fat-free mass (FFM) and total body weight (TBW). Dual energy X-ray absorptiometry was used to measure body composition. Measurements were performed at baseline and two-years. <b>Results:</b> Baseline age, sex, and BMI were similar between groups. Greater decreases in BMI in SG vs. NS (-12.4 (-14.4, -9.8) vs. 2.2 (0.3, 3.5) kg/m², <i>p</i> < 0.0001) and within-group decreases in mREE (401.0 ± 69.5 kcal/d; <i>p</i> < 0.0001) in SG were seen. mREE/FFM decreased within the SG group (<i>p</i> = 0.006), the two-year change in mREE/FFM and mREE/TBW did not differ between groups (<i>p</i> = 0.14 and 0.24). There was no metabolic adaptation within SG. <b>Conclusions:</b> Despite significant decreases in BMI after SG in youths, no metabolic adaptation was present at two years. This implies that by two years, metabolism has reached a steady state and weight changes after this should be addressed in an unbiased way.