There are two main reasons that eating breakfast can lead to hunger later in the morning: One is the adaptive function of our body to conserve energy when we do not eat. It goes back to the caveman days: if there wasn't food around, our metabolism would slow down to conserve energy. Our bodies work the same way today: if we don't eat breakfast, our metabolism slows down and we are less hungry as a result. Some people don't get hungry till late in the afternoon if they don't eat breakfast--they skip lunch as well! But, as I mentioned, they almost always make up for it later in the day. If we eat breakfast, our metabolism starts running: "we have plenty of energy to use," our body says, "so let's start using it!" If we don't keep eating we get hungry in a few hours. It's okay to eat again then--just be sure to have a snack that's not too high in calories, such as a handful of nuts or a few crackers with peanut butter. Then you won't be starving at lunch time!
The other factor that causes people to be hungry a few hours after breakfast is the drop in blood sugar. Often at breakfast we eat foods that are high in carbohydrates and low in fat and protein, such as a bowl of cereal and a glass of juice, or toast with jam. Our blood sugar spikes high in an hour or so, and drops quickly in another hour, leaving us dizzy and weak by mid-morning--way before lunch time.
