Objective.The aim of this study was to evaluate the effectiveness of a structured diet program in weight loss in patients with schizophrenia. Methods. A total of 38 outpatients diagnosed with schizophrenia according to DSM-IV and who had complaints of weight gain during treatment with various antipsychotic drugs were invited to participate in a 3-month structured diet program. Thirty-two patients and another 40 patients were included as the control group. At the beginning of the diet program, the patients were given a form in order to evaluate their eating habits, and blood samples were taken to measure plasma lipid profile, and fasting blood glucose (FBG) level. Patients' baseline weight, body mass index (BMI), and basal metabolism rate (BMR) were recorded. Results. Thirty-two patients with schizophrenia, who attended a 3-month structured diet program had mean weight loss of 6.19 kg, whereas patients in the control group gained 1.6 kg. Conclusion. Our findings show that a diet program is effective in managing antipsychotic-induced weight gain. The degree of weight loss seems to be correlated with the duration in which the patient is on the diet program. However; younger patients had less benefit from the diet program.