It really depends on the cat. I leave a bowl of food outside for the outside kitty and bowl inside for Catillac. I leave them full of food all day long. Then again, all I feed is dry. Perhaps the food your feeding isn't filling them up? For instance, Ol'Roy (the wal-mart brand) is corn based. It goes in and out without filling the pet up. Perhaps you need to buy a better, more filling, food?