Personally I would ride him with obscure insults every time he ate. Nothing overtly insulting but just enough that eventually he would get the hint and go hide like the animal he is to eat his feed. I once had a roommate (he was not fat) who would constsntly be on his computer in the living room and since he was Korean he felt the he had to eat with his mouth open, smack his lips and make all kinds of eating sounds. Took me about a week to get him to stop by pointing it out and calling him an animal every time he ate. Bad manners need to be pointed out and shunned.