Sure, a steak will fill you up, but most people aren't having steak for three meals a day. It's recommended that you have five portions of something throughout the day - three meals and a snack between breakfast/lunch and one between lunch/dinner. Then you won't be raiding cupboards at 11pm because what you ate throughout the day has kept you full.

Also, those smurfing oatmeal pies have like 310 calories a piece. No thanks.