If I eat a bowl of cereal, even unsweetened, I am ravenous and unproductive 2 hours later. On the other hand if I have 4-5 eggs or tin of sardines I'm good for

If I eat a bowl of cereal, even unsweetened, I am ravenous and unproductive 2 hours later. On the other hand if I have 4-5 eggs or tin of sardines I'm good for 4-5 hours.