Being the good Southern boy that I am, I was born and raised to "clean my plate". The determining factor in whether that tendency leads to obesity is what and how much is on a plate. I am anything but fat, and I always finish what is on my plate ... it is just the right thing to do, assuming, of course, that you don't pile your plate to overflowing with butter, lard, and mayonaisse.
Because we are taught to quit eating when the plate is empty, not when we are full, we never learn to quit when we have had enough. We need to rethink our training of children.