The South Beach diet was created by Dr. Arthur Agatson, who is a cardiologist. The diet was originally designed to help improve cholesterol and insulin levels, but it was observed that the resulting diet led to weight loss. Proponents of the South Beach diet believe that people on the diet can succeed, in part because the choices of proper foods on the diet result in dieters not feeling hungry between meals. That lack of hunger is seen as a key factor in maintaining weight loss.

The South Beach diet is not intended to be either a low-carbohydrate diet like Atkins, or a low-fat diet like more traditional diets. Instead, it promotes eating good carbohydrates and good fats. The South Beach diet emphasizes the use of vegetables and fruits in the diet more so than Atkins. It also places added emphasis on avoiding foods like fatty meats and butter. The fats that are encouraged in the South Beach diet are monounsaturated fats like olive oil and the omega-3 fatty acids found in fish.

The South Beach diet has a three-phase approach. In all of the phases, the dieter eats three full meals and two snacks per day. It begins with a two-week period in which the dieter learns to eat in a new way that is designed to promote healthy weight loss. During the initial two weeks, the dieter cannot eat any bread, rice, pasta, potatoes, baked goods, alcohol, fruit, candy, cake, sugar, ice cream, or cookies. In the second phase, some of those foods are re-introduced to the diet. There are books and charts that describe in detail which foods can be reintroduced, and by how much. The second phase should get the dieter to his or her goal weight. The final phase involves a lifetime commitment to continue to follow the dietary rules of the South Beach diet in order to maintain the desired weight.