Several WikiAnswerers' thoughts on the subject:
*People who don't have to deal with that issue have no idea how difficult it is.
*Fat people get made fun of for the same reasons anyone does-- the 'joker' is an insecure bully who has picked a socially-acceptable target in an attempt to make themselves feel superior. It is as insidious to the members of the target category as dwarf bowling and wet t-shirt contests.
*Fat people are unprotected, the way it has been deemed immoral to discriminate against ones race, beliefs, or motives. The last thing we have left is their blatant disregard for their health.
*I partially agree but not fully, fat people are being made of because of their size if you get made fun of because your fat don't get let down you gotta stay up at it but if someone does make fun of you go to a teacher who is overweight and tell him about the person
*Insecure people reassure themselves by making fun of others, and unfortunately, fat people are one of the few groups one can make fun of without legal retribution and very little fear of censure. It's the one of the last bastions of freely indulged in public incivilities.
*It is mostly because other people want to be cool like other people so the try to fit in with the group or people get abused and neglected so much they tease other people to get a rise out of them they forget what it is like to be teased and hurt