The overall purpose of this research is to look at how two of the most commonly prescribed newer antipsychotic medications, risperidone and olanzapine, affect substances in the body such as glucose and insulin. Undesirable changes in blood sugar control, or glucose regulation, and type 2 diabetes can occur more commonly in individuals with schizophrenia compared to healthy subjects and subjects with other psychiatric conditions. While abnormalities in glucose regulation were first reported in schizophrenia before the introduction of antipsychotic medications, antipsychotic treatment may contribute significantly to abnormalities in glucose regulation. Attention to the way that antipsychotic medications may affect glucose regulation has increased as doctors have become more concerned in general about disease- and drug-related medical complications, including weight gain during antipsychotic treatment.