Orthorexia nervosa is a term coined by 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.

A diagnostic questionnaire has been developed for orthorexia sufferers, similar to questionnaires for other eating disorders. A scientist proposes an initial self-test composed of two direct questions: "Do you care more about the virtue of what you eat than the pleasure you receive from eating it?

Treatment for orthorexia nervosa must begin with stabilizing any medical problems, if existent. Education about proper nutrition is an important part of treatment. People with orthorexia are often resistant to this part of treatment because they believe they know what a healthy diet is, and that their diet is healthy. They are proud of their dietary choices.

Symptoms of orthorexia nervosa may include obsession with healthy eating, emaciation, and death by starvation. Orthorexic subjects typically have specific feelings through different types of food.

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