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

Measured and predicted resting energy expenditure significantly decreased between baseline and after 9 months of weight loss intervention.

• Twenty-six adolescents with severe obesity (mean age 14.1 ± 1.5 years) completed a 9-month inpatient multidisciplinary intervention followed by a 4-month follow-up.
• Measured and predicted REE significantly decreased between T0 and T1 (P < 0.001).
• REE remained lower at T2 compared with T0 (measured REE: P = 0.017; predicted REE: P < 0.001).
• REE was assessed using indirect calorimetry and body composition was measured via dual X-ray absorptiometry.

Adaptive thermogenesis was present at the end of the 9-month weight loss intervention, as evidenced by predicted REE being significantly higher than measured REE.

• Adaptive thermogenesis was defined as a significantly lower measured versus predicted REE using regression models with baseline data.
• Two REE prediction equations were used: one incorporating both fat mass and fat-free mass (equation 1), and one using fat-free mass only (equation 2).
• Predicted REE using equation 2 (FFM only) was significantly higher than measured REE at T1 (P = 0.012), suggesting the presence of adaptive thermogenesis.
• Adaptive thermogenesis was observed independently of the degree of weight loss.

Baseline fat-free mass was negatively correlated with adaptive thermogenesis at T1.

• FFM at T0 was negatively correlated with ATp1T1 (Rho = -0.428; P = 0.033).
• FFM at T0 was negatively correlated with ATp2T1 (Rho = -0.485; P = 0.014).
• These correlations suggest that adolescents with lower baseline fat-free mass exhibited greater adaptive thermogenesis following the intervention.

The variation in fat-free mass between baseline and end of intervention was negatively correlated with adaptive thermogenesis at both T1 and T2.

• The variation of FFM between T0 and T1 was negatively correlated with adaptive thermogenesis at both T1 and T2.
• This finding suggests that greater losses in fat-free mass during the intervention were associated with more pronounced adaptive thermogenesis.
• The association persisted into the follow-up period (T2), indicating a sustained metabolic adaptation.

Adaptive thermogenesis was associated with subsequent body weight and fat regain during the 4-month follow-up period.

• AT was associated with subsequent body weight and fat regain following the intervention.
• The authors suggest adaptive thermogenesis may represent 'a damper to WL attempts while increasing the adolescents' risks for subsequent weight and adiposity rebounds.'
• The follow-up period lasted 4 months after the 9-month inpatient intervention.
• This is described as the first evidence of adaptive thermogenesis in response to weight loss and weight regain in adolescents with severe obesity.

This study represents the first investigation of adaptive thermogenesis in adolescents with severe obesity undergoing a multidisciplinary weight loss intervention.

• While effects of multidisciplinary weight loss on resting energy expenditure remain unclear in adolescents with obesity, the potential presence of adaptive thermogenesis had never previously been explored in this population.
• The study included 26 adolescents with severe obesity assessed at three time points: before intervention (T0), after 9-month intervention (T1), and after 4-month follow-up (T2).
• The authors describe their findings as 'preliminary results.'