Bulimia nervosa isn't just throwing up. Bulimia is binging and purging.
Binging - eating lots of food quickly in a short period of time
Purging - vomiting, laxative abuse, excessive exercise, or fasting
Bulimics don't binge and purge because they think they're fat or because of the media. They do it to gain a sense of control, to calm themselves. Bulimics rarely lose weight, their weight is usually up & down. 10% of bulimics will die from heart attack, malnutrition, or suicide
Eating disorders are coping mechanisms, not about vanity
I've had bulimia since I was 12. A typical binge for me is a pint of ice cream and a full box of macaroni & cheese. All eaten in a half hour, and it usually ends up regurgitated in to a trash bag. I don't do this because I want to be thin, I do it because it helps me cope w/ stress