Before you go down that path, don't. If you think life is hard now, you would be adding panic attacks over 10 calories in a stick of gum, wanting to cry because the number on the scale went up by 0.1lbs, and realizing you can't go out with anyone anymore because it would mean having to eat and please dear god don't make me eat I cannot eat, on top of it. It may seem logical to want to lose weight or starve now, but believe me when I say you will regret every minute of it once you're there. It consumes every aspect of your life. It is agonizing, both physically and mentally. Stop before you get to a point where you can't.
You will be so hungry you think you're going to throw up, so weak you want to (or do) pass out, your hair will fall out, your legs will go numb. You will be too hungry to sleep but desperate to sleep so you don't have to think about food anymore. You will panic if you can't purge or over exercise or are forced to eat. If something doesn't have calories listed, you will cry. It is actual hell on earth. And if you think you have control over it, trust me when I say you won't for long, you mind will be taken over.