Have you noticed how HUGE the dinner plates are these days? They are twice the size they used to be. Just like everything else. My mother-in-law bought me some small dessert plates for Christmas and they are actually the perfect size for dinner. I keep my portions low in order to fit everything on the plate. Try using a smaller dinner plate and see how much less you eat and realize you don't need any more.
Link to blog: http://thefitdivas.typepad.com/my_weblog/2009/04/use-a-smaller-plate.html