My pediatrician said most of them do this. She said you just have to ride it out. Give them a selection of appropriate foods 5 times a day (3 meals, 2 snacks) and what they eat, they eat. He may love beans one day, the next day they're poison. Keep rotating them through, and one day he'll like them again. Don't fight about it though...not worth it, and it puts too much emphasis on food in general, eventually leading to eating disorders (or so the "experts" theorize now).