BACKGROUND: Diabetes is more common in people with schizophrenia than in the general population. AIMS: To explore the possible reasons for the association between diabetes and schizophrenia. METHOD: Diet and other lifestyle factors in patients with schizophrenia were reviewed as risk factors for diabetes. RESULTS: People with schizophrenia show features of the metabolic syndrome at the onset of illness, before treatment. They also eat a poor diet, take little exercise and have high rates of smoking. Food intake may be increased further by antipsychotic medication. Nutritional factors appear to have a key role in the development of diabetes in patients with schizophrenia and may also affect the outcome and severity of schizophrenia. A common pathway through which diet might contribute to the development of both diabetes and schizophrenia is proposed. CONCLUSIONS: Lifestyle factors may influence outcomes in both diabetes and schizophrenia. Lifestyle interventions are the key to improving the long-term health of people with schizophrenia.