Why does your guinea pig eat so much?
"He is a pig" is your typical and unedgucated response to this question, but the truth is that they should eat 6-8 oz. of food each day. Keep it on a strict diet of 2 treats a day, with 1 baby carrot or so. I would suggest calling a vet for advice, as this may be signs of a rare, but dangerouse illness.