Why do so many girls, think they're fat when they aren't?

Almost every week when I'm at church I hear one of the young women complaining that they're fat and ugly. This bothers me to no end because after they finish the comment I look at them and you couldn't get thinner than them if you tried. Since they think they're fat some of them become anorexic or bulimic to lose that "fat." There are probably more influences, but I think that the main one is the media. Everyday teenage girls look at a model and think that to be accepted in society as beautiful they need to look exactly like that. Whenever I hear a really thin girl say that she's fat, I think to myself, compared to who. If girls had a better person to look up to, other than some celebrity, than a good percentage of them could be successful becuase they can accept themselves for who they are.