This is a 2-yr study proposing to examine the effects of switching subjects from conventional and atypical antipsychotic agents to Aripiprazole on cardiovascular health indices in overweight and obese patients with Schizophrenia or Schizoaffective disorder. Thirty partially remitted patients with Positive and Negative Syndrome Scale (PANSS) score of less than 100, who have body mass index (BMI) of 26 or higher will be switched from their existing antipsychotic to aripiprazole over 2-3 weeks period using a clinician determined cross-tapering approach.The objective of the study is to examine cardiovascular health indices such as serum lipids, serum leptin, fasting blood sugar, body weight and blood pressure. This study also examines the safety of switching to Aripiprazole with respect to changes in clinical state, preexisting or emergent side-effects, how brain processes information and changes in social functioning and quality of life.