Decrease of energy expenditure causes weight increase in olanzapine treatment - a case study.

The aim of this study was to evaluate the mechanisms underlying weight gain induced by the atypical antipsychotic, olanzapine. We performed euglycemic, hyperinsulinemic clamp combined with indirect calorimetry on a 48-year-old male with antisocial personality disorder, alcohol dependence and paranoid ideation before and after one month of olanzapine (10 - 15 mg/day) therapy. The patient gave his informed, written consent for this study. The results were a weight gain of 6 kg and a decrease in both basal (from 1673 to 1613 kcal/24 h) and 3-hour (from 22.8 to 20.2 cal/kg fat free mass/min) energy expenditure. Serum thyroid hormone and high-density lipoprotein cholesterol levels decreased, and the triglyceride and low-density lipoprotein cholesterol levels increased. Insulin sensitivity did not change. We conclude that decreased basal energy expenditure may contribute to weight gain in olanzapine treatment.