If there's one thing I learned in Kindergarten, it's that kids are merciless with their insults.
If the slightest thing is off about you - if you're wearing different clothing or you've got overly large glasses or have to use an inhaler, there will always be a group of kids there to make fun of you for it.
Good parents teach their kids out of making fun of others based on superficial things that may be out of their control, but unfortunately, some of those kids grow up to become adults who think it's OK to make fun of someone based on their looks. This is especially true of women's bodies. For example, a quick search on the Internet or look in the comments section of any Instagram post of a woman, and there'll be someone criticizing her body.