Adaptive thermogenesis in response to weight loss and weight regain: first evidence in adolescents with severe obesity

While the effects of multidisciplinary weight loss (WL) on resting energy expenditure remain unclear in adolescents with obesity, the potential presence of adaptive thermogenesis (AT) has never been explored, which was the objective of the present work. Twenty-six adolescents (14·1 (sd 1·5) years) with severe obesity completed a 9-month inpatient multidisciplinary intervention followed by a 4-month follow-up. Anthropometric measurements, body composition (dual X-ray absorptiometry) and resting energy expenditure (REE, indirect calorimetry) were assessed before (T0) and after 9 months of WL intervention (T1) and after a 4-month follow-up (T2). AT, at the level of REE, was defined as a significantly lower measured <i>v</i>. predicted (using regression models with baseline data) REE. Two pre-cited REE equations were used, using both fat mass and fat-free mass (FFM) (predicted REE using equation 1) or FFM only (predicted REE using equation 2). Measured and predicted REE significantly decreased between T0 and T1 (<i>P</i> < 0·001) and remained lower at T2 compared with T0 (measured REE: <i>P</i> = 0·017; predicted REE: <i>P</i> < 0·001). Predicted REE using equation 2 was significantly higher than measured REE at T1 (<i>P</i> = 0·012), suggesting the presence of AT. FFM at T0 was negatively correlated with ATp1T1 (Rho = -0·428; <i>P</i> = 0·033) and ATp2T1 (Rho = -0·485; <i>P</i> = 0·014). The variation of FFM between T0 and T1 was negatively correlated with AT at T1 and T2. These preliminary results suggest the existence of AT in response to WL in adolescents with obesity, independently of the degree of WL. AT was associated with subsequent body weight and fat regain, suggesting AT may represent a damper to WL attempts while increasing the adolescents' risks for subsequent weight and adiposity rebounds.