Appearance matters to some extent, but not enough to let it rule your life. If you think people will like you more if you look a certain way on the outside, chances are you're not going to like the people who think that way. They are usually incredibly superficial and not worth your time. Here's a picture of Kate Moss, who is rather notorious for being too thin. People that think women look good this skinny are definitly odd.
Statistics vary from study to study.
The following information was given to me by the University of Iowa Hospitals and Clinics and Linden Oaks Hospital during my treatments there. So if you get a group of 10 high school girls together at a party or some such, chances are at least two of them take out emotions on food in one way or another. Ninety percent of victims are female, ten percent are males. It is the highest of all mental disorders. What to Do Approching someone you suspect has eating problems is never easy.