Please explain these eating disorders?!

Please explain these eating disorders?

Ok, I basically know the jist of what anorexia and bulimia are, but I still don't understand something.

The whole disease starts because people think they are too fat, so they either starve themselves, or they make themselves throw up so they can lose weight.

After a while of doing this, they begin to lose weight, to the point where they look like skeletons, however, when they look in the mirror, they still see a "fat person". That's the part of the disease I don't understand. How could you possibly still think you are fat when you can see your rib cage through your clothes?

I'm not trying to be rude, I am just trying to understand because I just can't comprehend that part. I understand clearly how it starts (not saying I agree), but I don't understand how someone could weigh 80 lbs, rib cages popping out from under their skin, and still think they are fat??!!

i'm anorexic, and i'm definetely not perfect. people will sit there and say "you're so skinny" but to yourself, you're never good enough. once you get to that low weight, it's more of a fear of gaining weight if you start eating normal again.