In their search for dietary purity, they may become so restrictive about what they eat that they become as dangerously thin as an anorexic; for example, they may over do the avoidance of fatty foods, those with preservatives, and those with salt or sugar; to such a degree that there are very few choices available.
Source of the term orthorexia nervosa
The word, and the identification of the condition, is attributed to a Colorado specialist, Dr. Steven Bratman, who published a book on the subject. He coined orthorexia in 1997 (based on the pattern of anorexia) which comes from Greek orthos, "correct" or "right" plus orexis, "appetite". The word is beginning to appear in the United States and Britain, largely as a result of his book.
Most often, orthorexia is merely a source of psychological distress, not a physical danger. However, emaciation is common among followers of certain health food diets; such as, "raw foodism", and this can at times reach the extremes seen in anorexia nervosa.
Such "anorexic orthorexia" is just as dangerous as anorexia; however, the underlying motivation is quite different. While an anorexic wants to lose weight, an orthorexic wants to feel pure, healthy and natural. Eating disorder specialists may fail to understand this distinction, leading to a disconnect between orthorexic and physician.