Eat fiber. Fiber fills you up, is good for your digestive system, and generally takes a while to eat. Eating a bowl of ice cream will make you hungry in an hour; eat three apples, and you’ll be set for the whole evening. Most people cannot even eat that much. Eat fruits and vegetables in their natural forms, as much as possible. For instance, fresh apples are better than apple sauce and both are better than apple-flavored cereal.