Energy expenditure and physical activity in clozapine use: implications for weight management

Objective: The management of atypical antipsychotic-induced weight gain is a significant challenge for people with mental illness. Fundamental research into energy metabolism in people taking atypical antipsychotic medication has been neglected. The current study of men with schizophrenia taking clozapine aimed to measure total energy expenditure (TEE) and energy expended on physical activity - activity energy expenditure (AEE) and to consider the clinical implications of the findings. Method: The well-established reference method of doubly labelled water (DLW) was used to measure TEE and AEE in men with schizophrenia who had been taking clozapine for more than 6 months. Resting energy expenditure was determined using indirect calorimetry. Results: The TEE was 2511 606 kcal day(-1) which was significantly different to World Health Organization recommendations (more than 20% lower). The Physical activity level (PAL) was 1.39 +/- 0.27 confirming the sedentary nature of people with schizophrenia who take clozapine. Conclusions: The findings support the need for weight management strategies for people with schizophrenia who take clozapine to focus on the enhancement of energy expenditure by increasing physical activity and reducing inactivity or sedentary behaviours, rather than relying primarily on strategies to reduce energy intake.