It was designed by Dr. Agatston, a cardiologist. There are 3 phases. The first phase is 2 weeks long & its aim is to stabilize insulin levels & reduce carb cravings. In this stage you basically only eat (non-starchy) vegetables, protein, & unsaturated fats, including low-fat dairy. It's quite strict, but you are allowed to have a snack between meals. (estimated weight loss of 8lb or more according to the original book) The second phase lasts as long as it takes to get to your target weight at an estimated weight loss of 1lb/week. In this stage you slowly and moderately re-introduce healthy carbs in the form of fruits & whole grains. The third phase is maintenance.