The program is simple: you eat 3 meals a day and have 3 snacks. You keep a score of each item you eat or drink based on the book's simple 0-to-10 scoring charts. You can not score more then a set number each day: 30 for men, 25 for men trying to lose weight etc.The scoring is based on the Glycemic Index (so simple carbs score high for example) and the reason the program works is because it keeps blood sugar levels balanced all day and thus keeps the metabolism burning food instead of creating fat.