Influence of resting energy expenditure on weight gain in adolescents taking second-generation antipsychotics

Background & aims: : Weight gain is an undesirable side effect of second-generation antipsychotics (SGAs). We performed this study to examine the influence of SGAs on resting energy expenditure (REE) and the relationship of REE to weight gain in adolescent patients. Methods: Antipsychotic-naive or quasi-nave (<72 h of exposure to antipsychotics) adolescent patients taking olanzapine, quetiapine, or risperidone in monotherapy were followed up for one year. We performed a prospective study (baseline, 1, 3, 6, and 12 months after treatment) based on anthropometric measurements, bioelectrical impedance analysis, and indirect calorimetry (Deltatrac (TM) II MBM-200) to measure REE. We also analyzed metabolic and hormonal data and adiponectin concentrations. Results: Forty-six out of the 54 patients that started treatment attended at least 2 visits, and 16 completed 1 year of follow-up. Patients gained 10.8 +/- 6.2 kg (60% in the form of fat mass) and increased their waist circumference by 11.1 +/- 5.0 cm after 1 year of treatment. The REE/kg body mass ratio decreased (p = 0.027), and the REE/percentage fat-free mass (FFM) ratio increased (p = 0.007) following the fall in the percentage of FFM during treatment. Weight increase was significantly correlated with the REE/percentage FFM ratio at all the visits (1-3-6-12 months) (r = 0.69, p = 0.004 at 12 months). Conclusions: SGAs seem to induce a hypometabolic state (reflected as decreased REE/kg body mass and increased REE/percentage FFM). This could explain, at least in part, the changes in weight and body composition observed in these patients. (C) 2011 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.