The South Beach Diet is one of the original low carb diets. It isn't so much about eliminating carbs completely as changing your eating habits to good carbs. South Beach Diet has three very different phases.
Phase One is the initial step of the diet and eliminates all carbs, starches and sugars from your eating habits. The literature explaining the diet suggests that you do phase one for at least two weeks to detoxify your body from the sugars and starches in your diet which should eliminate the cravings for the sugars and starches. Phase One is supposed to be the phase where you lose the most weight quickest. My household generally does phase one for a month or two. The weight loss isn't as high as the books predict but it is pretty consistent. Generally, we end Phase One when we are tired of the limited foods or start cheating more often than not.
Phase Two allows you to add back in whole wheat breads, brown rices, and all fruits. This step is supposed to be a period of slower but maintainable weight loss. My experience has been that I add in the breads and sugars in too quickly and with too much enthusiam and that I lose track of the careful meal planning that I use for Phase One and get entirely too relaxed.
Phase three is basically just maintaining your weight. There are no diet restrictions and you are free to move back to phase one or two at any time. Essentially, in the past I've gone quickly to Phase Three with a very short Phase Two.