Formulated in 1976 by Nathan Pritikin and was an early forerunner of dietary guidelines intended to maintain a healthy weight and fight heart disease. It is a low calorie, high bulk, low fat, and low cholesterol diet with an average of less than ten percent of daily calories from fat. It is almost entirely vegetarian and those who adhere to this diet avoid processed and fatty foods. Some people choose the Pritikin® diet because it does not restrict the amount of food that may be consumed in one sitting. Instead, the diet restricts the types of foods that may be consumed. The food restrictions are based on the average calories per pound for the ingredients of every meal which must be less than 400. To achieve this, the vast majority of foods in every meal must be low in calories and fat.