Lifestyle Intervention to Improve Insulin Sensitivity and Markers of Cardiovascular Risk in Prostate Cancer Survivors

* In this study, participants will be divided into two groups. One group will undergo intensive lifestyle changes (Lifestyle Intervention Group) designed by the Diabetes Prevention Group, and the other (Control Group) will follow the guidelines for healthy living established by the Food Guide Pyramid and the National Cholesterol Education Program. * All visits will take place at the General Clinical Research Center at the Massachusetts General Hospital. * At the initial visit, the following will be performed: Bionutrition evaluation; Oral Glucose Tolerance Test (OGTT); additional blood work and; Dual Energy X-Ray Absorptiometry (DXA) Scan. * After the initial visit, visits will be scheduled at 3, 6 and 12 months after and the above procedures will be repeated. * Participants will be randomized into one of the two study groups. Lifestyle Intervention Group: The goal for participants assigned to this group are to achieve and maintain a weight loss of at least 7% of initial body weight through a healthy low calorie, low fat diet and to engage in physical activity of moderate intensity. Control Group: participants in this group will receive standard nutrition and exercise recommendations from the Food Guide Pyramid and the National Cholesterol Education Program Step 1 diet to reduce body weight and increase physical activity.