Or you can make fun of fat people and don't care. It's the one thing you can change about your appearance and not doing so is a sign of irresponsible neglect of your own body that shouldn't be encouraged.
It's like making fun of a weird fashion choice or a silly haircut. It's not like making fun of someones hight or dick size or whatever.
I'm saying that as someone who was overweight most of his adult life.