The American Psychiatric Association’s (APA) Diagnostic and Statistical Manual of Mental Disorders 5th Edition  described feeding and eating disorders as:
Persistent disturbance of eating or eating-related behavior that results in the altered consumption or absorption of food and that significantly impairs physical health or psychosocial functioning. (p. 329)
Among this class of disorders are Anorexia Nervosa (AN), Bulimia Nervosa (BN), and Binge Eating Disorder (BED). Within feeding and eating disorders, only one diagnosis within this class of disorders can be given during a single episode. This approach was based on the significantly different clinical course, outcome, and treatment needs of each disorder despite similar psychological and behavior characteristics .
Orthorexia Nervosa (ON), a recently proposed eating disorder, is characterized by a fixation with eating healthy . Although on the surface society views healthy eating as a positive behavior, the functional impairment associated with obsessional preoccupation suggests that these behaviors can be problematic. While ON was not included as a distinct disorder in the DSM-5, some studies have suggested specific diagnostic criteria for ON. For example, Moroze et al.  proposed the following diagnostic criteria: the presence of obsessional preoccupation with eating healthy foods with a focus on quality and composition of foods (Criteria A) accompanied by two additional symptoms.
Potential accompanying symptoms include unbalanced nutrition due to a preoccupation with food purity, preoccupation and worries about consuming impure or unhealthy foods with the effect of food quality and composition on health, avoidance of foods perceived as unhealthy, excessive time spent reading about, acquiring, and preparing foods, feelings of guilt and worry subsequent to consuming unhealthy foods, intolerance to different food beliefs, or spending excessive money relative to one’s income on food based on perceived quality . Moreover, the food obsessions interfere with physical health due to nutritional imbalances or lead to clinically significant distress or impairment in social, academic, or vocational functioning.
All studies with suggested criteria for ON have consistently indicated three primary diagnostic criteria: obsessive or pathological preoccupation with healthy eating, emotional consequences of non-compliance to self-imposed nutritional rules, and psychosocial impairments in areas of life as well as malnutrition and weight loss . Moreover, suggested criteria emphasized avoidance of foods considered unhealthy and positive effects of adherence to healthy eating rules. ON is thought to result in social isolation, malnutrition resulting in severe medical conditions, substantial dietary restrictions, and affective instability . Moreover, foods that contain significant amounts of fat, sugar, salt, or other unhealthy components are avoided, and food preparation becomes a vital part of the obsessive thoughts and compulsive behaviors.
While ON may appear similar to other eating disorders, it differs in that the preoccupation revolves around the quality of food rather than the quantity . Moreover, it is believed that ON does not stem from a preoccupation with physical appearance but rather through other mechanisms, including a motivation to improve one’s nutritional lifestyle. Furthermore, ON is thought to develop out of efforts to alter negative eating habits or increase positive eating habits to prevent or treat illnesses . While the goal appears to be enhancing quality of life, ON can result in various negative outcomes (e.g., malnourishment).
ON also differs from healthy eating habits. Suggested diagnostic criteria emphasized individuals with ON follow restrictive diets based on needs or medical conditions the individuals do not possess . Additionally, they may insist on the health benefits of such diets despite contradicting evidence. The preoccupations and beliefs about food demonstrate a dichotomous nature in which foods are perceived as either “all good” or “all bad,” differing from suggested limitations of certain foods outlined in various healthy eating guidelines. Moreover, the preoccupations and behaviors may contribute to malnourishment ; this is the opposite effect expected from following suggested dietary guidelines. Moreover, the healthy eating guidelines set forth by individuals with ON are exaggerated, and emotional distress results from transgressions .
The lack of formal criteria for the diagnosis of ON has led to a debate regarding whether it is a standalone diagnosis or part of another condition, including obsessive-compulsive disorder, addictions, or other eating disorders . This debate is further fueled by the shared characteristics and consequences between ON and other disorders. Nonetheless, those with ON are focused on being healthy and are often open about their non-sensible food beliefs. However, ON has been demonstrated as highly prevalent in individuals’ post-treatment for AN and BN .
Additionally, prevalence rates have been reported with great variance, likely because of the lacking psychometric properties of diagnostic measures, undefined formal diagnostic criteria, and cultural differences . Prevalence rates have been reported at ranges between 6.9–88.7%; the most commonly used tools to assess ON are the Bratman Orthorexia Test (BOT) and the ORTO-15, yet both measures lack validity . Moreover, most measures that have been created to assess ON have utilized international samples and were validated in languages other than English, further limiting their use on a U.S. sample. Additionally, studies of ON to date have focused mainly on university students, thus limiting their generalizability. Nonetheless, it has been reported that many professionals within the eating disorder field are aware of this condition and observe it within their practice .
Prevalence rates of eating disorders among minority women are generally unavailable due to the historical view that white women are more likely to meet criteria for eating disorders. However, recent research suggested prevalence rates of eating disorders are rising in both Western and non-Western countries and occur among all ethnic individuals at similar rates (National Eating Disorders Association; NEDA) . The typical age of onset was suggested to be between 10 and 30, and there is a female to male ratio of 10:1 for AN and BN . Importantly, eating disorders demonstrated high mortality rates: AN claims 5.1% per 1,000 persons per year and BN 1.74% per 1,000 persons per year.
Various psychosocial risk factors were associated with ON. In terms of demographic risk factors, there are mixed findings regarding age. Some studies identified ON to be more common among younger individuals. For example, in a sample of Italian athletes, Segura-Garcia et al.  found ON to be more common among younger adults (N = 734). Others, however, have suggested the risk of ON to increase with age. Varga et al.  found as age increased, ON did as well. Alternatively, higher quality studies did not find significant correlations between ON and age . In terms of gender, findings were also mixed, with some studies suggesting higher rates in females  and others suggesting higher rates in males . However, most studies of high quality suggested no relationship between gender and ON [7, 18].
Additionally, pre-existing or co-existing psychopathology were correlated with ON . Particularly, current or past history of eating disorder was significantly correlated with developing ON [5, 21]. Furthermore, drive for thinness  and internalization of a thin-ideal  were shown to correlate with ON. Moreover, eating habits, including avoiding certain foods, strict eating schedules, spending large amounts of time preparing food, restricting food intake, and consuming less saturated fats were indicated as risk factors for ON . Within these findings, mechanisms suggested to contribute to ON included preoccupation with fear of weight gain or clean eating as a trigger to preoccupation with weight and shape which is seen in other eating disorders.
Past research has been somewhat inconsistent in identifying ON as a separate diagnostic category. The present study could further shed light on this diagnostic category and bring its existence and adverse effects into awareness for both individuals and mental health and medical providers. Moreover, identifying sex, racial, and age differences among individuals who meet criteria for ON is crucial in providing proper care to all individuals struggling with this disorder. Two research hypotheses and three research questions have been formulated.
Based on the findings from the literature, the following hypotheses were proposed:
History of an eating disorder will be a predictor of severity of ON symptomology.
History of eating disorder related treatment will be a predictor of severity of ON symptomology.
Research Question 1
The preceding literature has indicated mixed findings regarding sex differences and ON symptomology. However, a majority of studies to date suggest no significant sex differences. Based on these findings taken together, in this study we aimed to determine whether sex differences exist in severity of ON symptomology.
Research Question 2
Eating disorders have historically been recognized as disorders that only affect white women. However, recent research suggests individuals of racial minorities suffer from eating disorders at similar rates to white individuals. Based on these findings, in this study we aimed to determine whether racial differences exist in severity of ON symptomology.
Research Question 3
The preceding literature has indicated mixed findings regarding age and ON symptomology. However, higher quality studies to date suggest no significant age differences. Based on these findings taken together, in this study we aimed to determine whether age group differences exist in severity of ON symptomology.