DS (12 months) has been signing "all done" at the end of meals for a while now (well, his own version of it anyway). But lately he has been signing it when he has hardly eaten anything. If he just wants to get down from his high chair or if there is no more of whatever food he prefers at a particular meal, he will sign "all done" even though he's not full. Then if I let him down, he will spend the next half hour coming to me and begging for food.
I try to hold him off by telling him he's not all done yet and by "bribing" him. I'll say, "If you eat another bite of oatmeal, you can have another piece of cheese." It usually works for a few bites, but the things that he wants more of are typically the things I want to limit his intake of. (He would eat nothing but cheese for three meals a day if I let him.)
He's still to young for me to use the "ok, but if you get down, you don't get any more food until lunch/dinner" strategy with him, so I don't know how to break this habit. I also don't want to get into the habit of force-feeding him if he says he's done. Any suggestions?