The National Institute of Mental Health convened a meeting in October 2005 to review the literature on obesity, nutrition, and physical activity among those with mental disorders. The findings of this meeting and subsequent update of the literature review are summarized here. Levels of obesity are higher in those with schizophrenia and depression, as is mortality from obesity-related conditions such as coronary heart disease. Medication side effects, particularly the metabolic side effects of antipsychotic medications, contribute to the high levels of obesity in those with schizophrenia, but increased obesity and visceral adiposity have been found in some but not all samples of drug-naïve patients as well. Many of the weight-management strategies used in the general population may be applicable to those with mental disorders, but little is known about the effects of these strategies on this patient population or how these strategies may need to be adapted for the unique needs of those with mental disorders. The minimal research on weight-management programs for those with mental disorders indicates that meaningful changes in dietary intake and physical activity are possible. Physical activity is an important component of any weight-management program, particularly for those with depression, for which a substantial body of research indicates both mental and physical health benefits. Obesity among those with mental disorders has not received adequate research attention, and empirically-based interventions to address the increasing prevalence of obesity and risk of cardiovascular and metabolic diseases in this population are lacking.