Overweight/obesity is a growing concern throughout the general population. The prevalence of overweight and obesity in schizophrenia is high, compounding the burden of an already devastating illness. This is making overweight/obesity an important consideration if the physical health of patients is to be improved. Ultimately, overweight/obesity results from an imbalance between food intake and energy expenditure over several years. However, the pathophysiology of overweight/obesity is complex and involves interactions between environmental, behavioural and genetic factors. There is compelling evidence that patients with schizophrenia are more prone to weight increase than the general population. Although a number of social factors contribute to the increased risk of overweight/obesity and metabolic disturbances in patients with psychiatric disorders, there is also evidence that genetic factors may play a role. Additionally, many psychiatric medications are known to be associated with weight gain. It is thought that weight gain may be related to neurotransmitter-receptor affinity, which can have multiple effects on energy homeostasis. For example, histamine H1 receptor affinity has been shown to predict short-term weight gain with both typical and atypical antipsychotics.

Obesity, especially abdominal obesity, is associated with a number of adverse health consequences. These include an increased risk of glucose intolerance, insulin resistance, Type 2 diabetes, dyslipidaemia, hypertension and cardiovascular disease. In addition, the presence of metabolic syndrome, a cluster of metabolic disturbances, significantly increases the risk of cardiovascular morbidity and mortality. It can therefore be seen that there is an urgent need to start identifying schizophrenia patients who are at risk to help improve long-term health outcomes.