Orthorexia, or orthorexia nervosa is a term coined by Dr. Steven Bratman, a Colorado MD, to denote an eating disorder characterized by a fixation on eating what the sufferer considers to be healthful food, which can ultimately lead to early death.

Bratman coined the term in 1997 from the Greek orthos, "correct or right", and orexis for "appetite". Literally "correct appetite", the word is modeled on anorexia, "without appetite". Bratman describes orthorexia as an unhealthy obsession (as in obsessive-compulsive disorder) with what the sufferer considers to be healthy eating. The subject may avoid certain foods, such as those containing fats, preservatives, or animal products, and suffer malnutrition

As of January 2007, two peer-reviewed studies have been published on the condition. In the studies, Donini et al define orthorexia nervosa as a "maniacal obsession for healthy foods" and propose several diagnostic criteria. Sufferers of orthorexia often display symptoms consistent with obsessive-compulsive disorder and have an exaggerated concern with healthy eating patterns. A diagnostic questionnaire has been developed for orthorexia sufferers, similar to questionnaires for other eating disorders.

Symptoms and their possible explanations:
Symptoms of orthorexia nervosa may include obsession with healthy eating, emaciation, and death by starvation. Orthorexic subjects typically have specific feelings towards different types of food. Preserved products are described as "dangerous", industrially produced products as "artificial", and biological products as "healthy". Sufferers demonstrate a strong or uncontrollable desire to eat when feeling nervous, excited, happy or guilty. Orthorexia nervosa has a higher prevalence in men and in those with a lower level of education.

There has been no investigation into whether there may be a biological cause specific to orthorexia nervosa. However, Donini et al link orthorexia to a food-centered manifestation of obsessive compulsive disorder, which is thought to have specific biological causes