This is something weird I've noticed lately. I don't know, but is it possible for your stomach to shrink or something? I've lately gotten to where I get full SO much quicker than I ever did before. It almost seems "too fast". As in, eating a frozen dinner, I'll get grossly full before I'm 3/4th done with it. So not a big portion of food---in fact what some may consider to be too small a portion--I can't finish. This has happened in restaurants and in front of other people(and you know how big restaurant portions can be!) and I'm sure they think I'm "starving" myself or doing it on purpose for dieting reasons when I'm finished and I still have over half my plate left!
I've also noticed that I can't really "push" food on myself like I once could. When I reach this new found "fullness" point, I lose all interest in this food. Previously, I could push it if I wanted and overeat. I don't think this is just in my head, it's an obvious change that I don't have anything to do with! Normal? lol