Anorexia is NOT a quick weightloss plan- you cannot decide to 'become anorexic' for a couple of weeks so that you can fit into your prom dress. Not eating so that you'll look good on holiday isn't anorexia, it's stupidity.
Anorexia isn't even really a wish to lose weight- it's about wanting to vanish from everyday life, wanting to escape, wanting to die even. True anoretics don't think "wow,I'm so thin and sexy now, I'm going to wear my tiny miny skirt and show off my skinny legs now". They usually know they look like shit with hair on their body, protruding bones and grey skin, but what they look like isn't important any more.
Oh yeah, and you can't just 'get better', either. Most sufferers of anorexia are never truely cured, if at all. A majority of the thoughts stay with you forever, even if you start eating normally.
Not anorexia - "Oh my God! I've not eaten for like TWO days, I'm SO anorexic. But I want to fit into that size 2 skirt for Saturday"
Anorexia - "Shit! I've put on a pound! I'm fucking shit, I'm a total failure, why am I even here? I can't even lose weight any more. I'm just crap at everything. I'm a huge fat waste of fucking space!"