age definately has nothing to do with anorexia. Or bulimia for that matter. people who are 30 and 40 can have it. there is no age limit. I think people think that anorexia and bulimia only happens with young people because they are more vulnerable to developing those behaviors. there are some cases where people grow up and still dont know that being to thin is not healthy. so therefor, they can become anorexic and not know it.
But there are also people that just have a really fast metabolism. And when they have a really fast metabolism, they can eat so much and not gain an ounce.