It depends on the calorie intake in a day. Eating sugar-free or low-sugar oats for a long time in the morning is very nutritious and can bring a strong feeling of fullness. You can also eat light and low-fat meat, eggs and milk products to supplement protein. Although protein is high in calories, it is very nutritious, and it takes a lot of calories for the human body to digest protein. The best ratio of three meals is 3:4:3. Be sure to eat less dinner. Usually eat seven points full.