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

While the effects of multidisciplinary weight loss 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±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 weight loss intervention (T1) and after a 4-month follow-up (T2). AT, at the level of REE, was defined as a significantly lower measured versus predicted (using regression models with baseline data) REE. Two precited REE equations were used, using both FM and FFM (REEp1) or FFM only (REEp2). Measured and predicted REE significantly decreased between T0 and T1 (p<0.001) and remained lower at T2 compared with T0 (REEm: p=0.017; REEp: p<0.001). REEp2 was significantly higher than REEm at T1 (p=0.012) suggesting the presence of AT. FFM at T0 was negatively correlated with ATp1T1 (Rho=-0.428; p=0.033) and ATp2T1 (Rho=-0.485; p=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 weight loss attempts while increasing the adolescents’ risks for subsequent weight and adiposity rebounds.