A three hour diet plan is a meal plan that advises the user to follow a set pattern of eating. You need to consume a meal or a snack every three hours. The meal has to be small and sufficient. It can include any type of food item, but you must make sure that you avoid foods that are high on cholesterol and fat. High protein foods are a priority in this diet plan. There is no restriction as such and you can eat any food you like. But it is difficult to maintain a three hour diet plan when you are on a vacation or when you are eating out