The theory is based on the diet of how the ancient Romans ate. The diet is divided into a under eating phase during the day, which cleanses and detoxes the body. You only consume light foods, i.e. raw veggies, some fruit and light protein, such as yogurt or unprocessed whey protein. Then there is an evening phase of overeating, where consume a large sized meal, first with salad or veggies, then protein, and then a carbohydrate. This phase actually helps rev up your metabolism. You can eat as much as you want in the evening phase, just as long as it is from the right foods. Sound odd. But it works.