We have large plates with a big rim. The center part that isn't raised and slanted is about 7 inches, This allows me to make a satisfying looking pile of things on what looks like a big plate but is actually sensible portions. It triggers the response "I'm going to enjoy all this." And the later response, "I ate all that and I'm full, shut up leptin." The wide open spaces of a 12 inch plate could cause other responses for some people, even if you make highly satisfying foods.