One group will receive instruction on a low-calorie approach to weight loss (reducing caloric intake by approximately 500 calories per day). The other group will be instructed to follow a low-fat, low-glycemic index vegan diet. A vegan diet is one that does not contain any animal products (no meat, fish, poultry, eggs, or dairy) but emphasizes plant-based foods, such as fruits, vegetables, whole grains, and legumes/beans. In addition, this will be a low-glycemic index diet, which means you will be asked to favor foods that don't cause a quick rise in blood sugar (for example, choosing oatmeal over cornflakes for breakfast).