There are only a few notable scientific works that, in an attempt to explore the breadth and depth of the still vaguely-understood illness, have tried to identify which groups in society are most vulnerable to its onset. This includes a 2008 German study, which based its research on the widespread suspicion that the most nutritionally-informed, such as university nutrition students, are a potential high-risk group for eating disorders, due to a substantial accumulation of knowledge on food and its relationship to health; the idea being that the more one knows about health, the more likely an unhealthy fixation about being healthy can develop. This study also inferred that orthorexic tendencies may even fuel a desire to study the science, indicating that many within this field might suffer from the disorder before commencing the course. However the results found that the students in the study, upon initial embarkation of their degree, did not have higher orthorexic values than other non-nutrition university students, and thus the report concluded that further research is needed to clarify the relationship between food-education and the onset of ON.Similarly, in a Portuguese study on nutrition tertiary students, the participants orthorexic scores (according to the ORTO-15 diagnostic questionnaire) actually decreased as they progressed through their course, as well as the overall risk of developing an eating disorder being an insignificant 4.2 percent.
As evidenced by the following:

Compulsive behavior and/or mental preoccupation regarding affirmative and restrictive dietary practices believed by the individual to promote optimum health. (Footnotes to this criteria add: Dietary practices may include use of concentrated "food supplements." Exercise performance and/or fit body image may be regarded as an aspect or indicator of health.) Violation of self-imposed dietary rules causes exaggerated fear of disease, sense of personal impurity and/or negative physical sensations, accompanied by anxiety and shame. Dietary restrictions escalate over time, and may come to include elimination of entire food groups and involve progressively more frequent and/or severe "cleanses" (partial fasts) regarded as purifying or detoxifying. This escalation commonly leads to weight loss, but the desire to lose weight is absent, hidden or subordinated to ideation about healthy food.Criterion B. The compulsive behavior and mental preoccupation becomes clinically impairing by any of the following:

Malnutrition, severe weight loss or other medical complications from restricted diet
Intrapersonal distress or impairment of social, academic or vocational functioning secondary to beliefs or behaviors about healthy diet
Positive body image, self-worth, identity and/or satisfaction excessively dependent on compliance with self-defined "healthy" eating behavior.A diagnostic questionnaire has been developed for orthorexia sufferers, similar to questionnaires for other eating disorders, named the ORTO-15. However, Dunn and Bratman critique this survey tool as lacking appropriate internal and external validation. Epidemiology
Results across scientific findings have yet to find a definitive conclusion to support whether nutrition students and professionals are at higher risk than other population subgroups, due to differing results in the research literature.