I was "actively aneroxic" for about 2 years when I was in junior high/high school and once reached 85 lbs at 5'4". I did not seek treatment, but eventually stopped the behavior. Although my thought patterns remained the same, I have not actively restricted my food to the same degree, and am a healthy 120 lbs.
Now, however, perhaps due to some circumstances in my lfe, I find my thought patterns about my weight growing increasingly obsessive and harmful. Should I seek help at this point, even though I am not restricting my diet in harmful ways?
While the precise cause for anorexia nervosa is not known, the current thinking is that this severe illness develops in individuals who have a particular biological vulnerability and whose environment introduces them to weight loss for any of a number of reasons. If indeed you had developed anorexia nervosa some time ago, you likely still carry with you the vulnerability to struggling with this issue again. I would certainly recommend an evaluation session with someone who has experience in the treatment of eating disorders in order to assess your risk and offer you support, information, and possible treatment options.