Background: People with psychosis often experience weight gain, which places them at risk of cardiovascular disease, diabetes, and early death. Objective: To determine the uptake, adherence, and clinical effectiveness of a healthy living intervention designed to reduce weight gain. Method: An exploratory randomized controlled trial, comparing the intervention with treatment as usual (TAU) in 2 early intervention services for psychosis in England. DSM-IV classification was the diagnostic criteria used to assign the psychiatric diagnoses. The primary outcome was change in body mass index (BMI) from baseline to 12-month follow-up. The study was conducted between February 2009 and October 2012. Results: 105 service users, with a BMI of ≥ 25 (≥ 24 in South Asians), were randomized to intervention (n = 54) orTAU (n = 51) after stratification by recent commencement of antipsychotic medication. Ninety-three service users (89%) were followed up at 12 months. Between-group difference in change in BMI was not significant (effect size = 0.11).The effect of the intervention was larger (effect size = 0.54, not significant) in 15 intervention (28%) and 10TAU (20%) participants who were taking olanzapine or clozapine at randomization. Conclusions: The healthy living intervention did not show a significant difference in BMI reduction compared to the TAU group. © Copyright 2014 Physicians Postgraduate Press, Inc.