orexi-, orex-, -orexia, -orexic, -oretic, -orectic, -rexia (Greek: appetite [hunger]; to stretch out for; to desire).
Instead of having an obsessive desire to lose weight, sufferers from orthorexia apparently have an unhealthy obsession with healthy eating. 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.
The word, and the identification of the condition, is attributed to a Colorado specialist, Dr. Steven Bratman, who has recently 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.