Because steamed bread, steamed buns and other foods are pasta, that is to say, the main component is carbohydrate, which is simply starch. When it enters the body, it is converted into sugar, which is easily digested and absorbed. This is the main reason why you are more hungry. Of course, your exercise can easily lead to hunger. If your job doesn't allow you to eat at normal hours, I suggest you add a poached egg to your breakfast. Foods high in fat and protein can delay digestion and be more resistant to hunger.