Breakfast cereals and satiety: scientists examine potential
Cereals themselves are not very filling. Now I don't really care whether I'm hungry or not - I eat when I need to eat, not because I'm hungry. However for 'grazers' who eat all day (btw I keep telling you people to eat protein fluff), it was found that adding gums in the cereal will increase satiety.
That said, cereals should not be eaten by itself for the reason that you'll just get hungry again in a minute.