Miami cardiologist Arthur Agatston developed the South Beach diet as a way for his heart patients to lose weight in a healthy, sustainable way. Based on the Glycemic Index (GI), which ranks foods based on their effect on blood sugar levels (the smaller the effect, the lower the GI value), the diet focuses on eating the 'right' carbs and the 'right' fats. In practice, the diet severely restricts carbohydrates in the first two weeks (Phase 1), before gradually re-introducing those with a low GI value (Phase 2). The South Beach Diet claims you can lose 8-13 pounds during Phase 1 and 1-2 pounds per week during Phase 2.
