How much does he actually eat in a day, if given free rein?
My five month old kitten eats a lot...four or five pouches of wet food, a full bowl of dried food, a 1/3 of a bottle of kitten milk and as much else as he can scrounge or scavange off plates. He poops at least three times a day. He's not particularly big (neither are his mum or sister though) but is extremely active and looks very fit and trim and healthy to me. I don't recall our last kittens eating as much at this age, but I'm kind of assuming that he's like my lanky lively seven year old..it takes a lot of calories to keep up that level of activity plus grow all the muscle and bone etc to get to adulthood. My daughter eats nearly as much as her father, but I don't think of her as greedy, just needing the nutrients. It would be different if she was getting tubby or conversely losing weight, or if she didn't seem well despite the food.