Hi Christina! Well it depends how much you feed him!! You only need to give him about 2 spoon fulls of hamster food a day. Don't over feed him or he will go BOOM!
Your hamster can be naturally large, but to make sure, go to the vet to make. If it's because your feeding it to much, your vet will say what you need to do.
Don't full your hamster because people and pets are same when you eat much how do you feel don't feed it very much because they can die because of your fault..
You should give him/her not too much food cause if you over feed him/her it will die and if you have a baby hamster DO NOT carry it too much cause it will die good luck!!
Depends way kind of hamster it is
Your overfeeding him
Your probably feeding it to much.
My hamster is going trough puberty. His testicles got really big yesterday and I don't know what to do.