well one reason is that they actually see themselves as fat. in their mind they don't think they are skinny enough. also something that girls don't realize is that men actually see girls as lighter and skinnier than they are. men see women as much as 15 pounds lighter than they really are.
Uh, I'm not quite sure where you got that fact from, breakingfan2006. But anyway, girls who are chubby themselves and call other girls fat often do so as a way to make them feel better about themselves. They are insecure, bottom line.
Well for the same reason popular preppy people make fun of other people, to make themselves feel better about the way they look. If they make other people feel insecure about themself it gives them confidence.
Well I don't know about 'all' but it's because they have low self esteem, so they push down others to pull themselves up. It makes them feel better about themselves.
i was taught it and read it in my college psychology class
to make themselves feel better.. lol.. :)