The rate of type-2 diabetes mellitus (T2DM) is at least 2-3 times higher in persons with psychotic illnesses than in the general population. Life expectancy of individuals with psychosis is also 20-25 years less than the general population, primarily due to premature onset of cardiovascular disease (CVD). Despite the high risk for T2DM and CVD, psychotic illness has been an exclusion criterion in all large-scale studies of diabetes prevention and management. We propose a 3-year randomized controlled trial examining the effectiveness of a lifestyle intervention (LI) aimed at reducing caloric intake and increasing physical activity in overweight or obese individuals (N=150) suffering from both a psychotic illness and T2DM. Weight and glycemic control will be the primary outcome variables. It is hypothesized that a significant weight reduction and improvement in glycemic control will be found in those who receive the LI relative to those who do not.

Inclusion Criteria:

1. Between the ages of 18 and 70 years (inclusive)
2. DSM-IV-TR diagnosis of one of the psychotic disorders listed above
3. Body Mass Index (BMI) > 25 kg/m2 at the time of enrollment
4. Clearly documented diagnosis of type-2 diabetes mellitus or prediabetes
5. Ability to provide informed consent
6. No medical contraindication to participation in weight reduction / exercise program, determined in consultation with their primary care physician
7. Female participants, of childbearing potential, using a medically accepted means of contraception

Exclusion Criteria:

1. Inability to give informed consent
2. Currently enrolled in a formal structured weight management program
3. Currently being prescribed medication specifically for weight loss
4. Participants with unstable or active cardiovascular illnesses (myocardial infarction, CHF, etc), active or end-stage renal disease, unstable thyroid disease, etc.
5. Recurrent episodes of diabetic ketoacidosis, seizure or coma without warning or severe hypoglycemia