Anorexic question ?

You can't just "become" anorexic, and it is possible to lose 20lbs in a month on a very extreme ana diet, doesn't mean you're actually anorexic because you're under eating that much. At least 0-100 calories a day.
Of course at first your weight would just drop off when you start starving yourself, but when the persons anorexia gets progressively worse it's harder, and they lose weight because they stop binging, and restrict themselves.
Don't do this,
It's very unhealthy.
And can mess up your life.

anorexia is a mental disorder . eating almost nothing for a month doesn't mean someone is anorexic. it just means they have picked a very unhealthy way to lose weight.

You don't 'become' anorexic. You either are, or you aren't. You have to have a predisposition to develop an eating disorder. But yes, as well as losing hair, periods, gaining body hair, organ failure, fainting, bad skin, lack of bladder control, anorexics can lose weight really fast. Trust me they aren't the ones advertising anorexia as glamorous. It actually pisses sufferers off.

Some can lose that much in month. Some can't. It depends on the individual as everyone is different. Regardless, Anorexia Nervosa is not actually about weight loss. It is not a diet tactic. It's a disease. So you cannot "become" anorexic. Also losing that much weight in a month can cause far too many health complications.