To 14 or 15, or 1600 calories you get into nutrient deficiency - not enough vitamins, minerals and so forth. And of course that will not extend life span. So you have to increase the nutrient value of each calorie by selecting the foods that you eat carefully. From experiments with mice Roy has also shown you can t exercise the calories away and get the same benefit. Roy and his daughter Lisa invited me to find out for myself over dinner.
Some people prefer more protein, some less.
The main thing is calories. You have to lower the calories but keep it nutrient dense, and then it will work. On the other hand, critics argue that long-term, the diet leaves you permanently hungry and painfully thin, kills your sex drive, and takes the fun out of life in general and food in particular. Roy insists that moderation is the answer. And you don't have to stick to it every meal.