 The number of overweight and obese Americans has increased significantly in recent years. There are now many different diet plans being promoted by doctors and the media. The Atkins diet, a low carbohydrate nutritional plan, is especially popular; its advocates claim that following the diet will result in long-term weight loss with no negative effects. Another diet, called the Dietary Approaches to Stop Hypertension DASH diet, is a high carbohydrate diet designed to help treat and prevent high blood pressure. However, more thorough investigation of these claims is needed. This study will compare the short- and long-term effects of the Atkins diet to the DASH diet. This trial will enroll overweight and obese participants. 