One of the largest issues with weight discrimination (pun intended) is that people start to believe that they should all look one way.
To quote one of my favorite songs from my angsty teenage years, "These plastic molded seats had to be cast from someone's perfect ass, leaving the rest of us to squirm uncomfortably."
In other words, just because what we see in the media looks one way does not mean that the rest of us need to fit into that mold. That's just the way one person looks. It's not really necessary for us all to look that way.