Well the main play mode is fool around, its a sandbox game at heart isnt it? I normally hate these games, I mean how many fucking GTAs do we need, seriously. However Dead Rising is motherfucking goddamned zombies. From what ive seen id sorta like to think of it as AMPED in terms of what you do. There are a lot of goals, this giant mall, and lots of zombies. You can follow the main story, or you can try to make the most outrageous zombie situations ever.
I don't really see eating as a huge problem. I suspect it isnt like every 3 minutes.