No clue who OP is, but if it's not bullshit, it's anorexia by definition. Which I think is actually anywhere under 1500. Easily anything under 1000. It's called an eating disorder for a reason: under no circumstances is it acceptable. It is hazardous to your health 100% of the time.

Posting about it on a forum is a classic sign of a cry for help if I ever saw one.

So, maybe see a psych, or post about what's really upsetting you.