South Beach allows more complex carbs and less fat-no eggs fried in butter and eaten with bacon but rather eggs cooked with just a spray of fat and a little low fat cheese. In later stages fruit, whole grain bread, and the odd sweet potatoe are allowed. The greatest difference is that there is no emphasis on being in ketosis-the author does say that he thinks the dangers have been overblown but that is the only mention of ketosis in the entire book. I tend to be quite obssesive so not having to worry about that is a plus for me. South Beach is intended to be a diet to improve blood chemistry for cardic patients-wieght loss is sort of a side effect.