Orthorexia nervosa is a term initially coined by Bratman  to describe the pursuit of healthy eating that intensifies and becomes an excessive, pathological preoccupation with consuming only foods that are “healthy” and avoiding those that are “unhealthy.” Since, there has been much debate surrounding the conceptualization of orthorexia nervosa, and there remains no official consensus definition or diagnostic criteria to date [2–6]. Recent work has raised concerns about the over-diagnosis of orthorexia nervosa, risking the pathologizing and stigmatizing of followers of healthy diets, regardless of the presence of pathology [7–9]. For instance, as an eating disorder, orthorexia nervosa would be expected to have prevalence rates similar to other eating disorders, which are no higher than 2% . However, the literature has documented prevalence estimates for orthorexia nervosa ranging up to 88.7% in non-clinical populations . Additionally individuals who are vegan, vegetarian, or simply attempt to avoid processed foods are often being labeled as having orthorexia nervosa [7, 8, 11–13]. This is concerning considering the extensive body of evidence supporting that a healthy diet can enhance physical and psychological wellbeing (see e.g., [14–17]).
The pathology-driven approach to the study of orthorexia nervosa has left unstudied the normal, flexible, health promoting pursuit of a diet with a preference for healthy foods over unhealthy foods. Commonly used measures of orthorexia nervosa may not be accurately distinguishing between the pursuit of a healthy diet which is pathological and that which is not pathological [7, 13, 18, 19]. Although various measures have been developed, [13, 19], the Teruel Orthorexia Scale (TOS)  is perhaps the only measure which makes the distinction between the pursuit of a healthy diet which is beneficial (healthy orthorexia) and that which is pathological (orthorexia nervosa). Based on the TOS, both healthy orthorexia and orthorexia nervosa both reflect eating behaviors in which an individual dichotomizes foods into “healthy” and “unhealthy” categories. Healthy orthorexia, however, is thought to reflect the pursuit of healthy foods in a way which is health enhancing and non-pathological, which is in line with Bratman’s  argument that healthy diets can indeed be followed in the absence of pathology.
Studies using the TOS have found significant positive associations between the two constructs, and there is preliminary evidence to suggest that they have some conceptual overlap [20–22]. There is also increasing evidence supporting the two as conceptually distinct eating styles. Healthy orthorexia has been found to be positively associated with indices of wellbeing and inversely associated with negative affect, and orthorexia nervosa has been found to be inversely associated with indices of wellbeing and positively associated with indices of negative affect [20, 21, 23, 24]. Additionally, it has been proposed that the motives that drive healthy orthorexia and orthorexia nervosa may differ with the former being driven by health-concerns, and the latter by weight control . Recent work using the TOS to examine the typology of individuals based on orthorexic eating behaviors provides further support that healthy orthorexia diverges from orthorexia nervosa, with individuals with high healthy orthorexia and low orthorexia nervosa scoring higher on measures of self-esteem and intuitive eating, and those with low healthy orthorexia and high orthorexia nervosa scoring significantly higher on measures of anxiety, and depressive symptoms .
The surge in research on orthorexia nervosa has been paralleled by an increased interest in adaptive eating behaviors . Perhaps the most researched is intuitive eating, which refers to a set of flexible eating behaviors that are regulated by internal physiological cues rather than external emotional and situational cues [26, 27]. Individuals who eat intuitively trust and rely on their internal hunger and satiety cues to guide their eating behaviour, avoid labelling foods as forbidden, eat for physical reasons rather than as a way of coping with emotional distress, and make food choices which support or enhance their body’s functioning . Intuitive eating has been found to be associated with lower levels of binge eating, drive for thinness, situational eating, emotional eating, food anxieties, food preoccupation and rigid dietary constraint [29–37]. Furthermore, there is a strong body of evidence to support that indices of positive body image, namely, body appreciation, functionality appreciation and embodiment, are psychological resources that enhance intuitive eating by promoting the awareness of, and appreciation for the functions of the body [38–46]. Intervention programs aimed at the treatment and prevention of a wide variety of eating disorders are increasingly focusing on the enhancement of intuitive eating and positive body image resources, with encouraging results [36, 40, 44, 47].
Given the significant body of work supporting strong links between constructs of positive body image and eating behaviors, it is unsurprising that researchers are beginning to show interest in the relationships between these constructs and orthorexia nervosa. However, these studies are few, and have had mixed findings, providing evidence for both positive  and negative associations [49, 50] between orthorexia nervosa and indices of positive body image. In addition, most of these studies used questionnaires that may have classed both the pathological and non-pathological pursuit of a healthy diet as orthorexia nervosa . To the best of our knowledge, only one study has used the TOS to examine the links between healthy orthorexia and intuitive eating which found that individuals with higher healthy orthorexia and lower orthorexia nervosa are more likely to eat intuitively than those with lower healthy orthorexia and higher orthorexia nervosa .
The Present Study
In light of the commentary above, the conceptualization of healthy orthorexia offered by Barrada and Roncero  offers researchers a promising new avenue for exploring the pursuit of a healthy diet which is not pathological, and for differentiating this way of eating from orthorexia nervosa. Furthermore, intuitive eating, body appreciation, functionality appreciation and embodiment are constructs which seem to play an important role in promoting eating behaviors that are adaptive and health enhancing, and reducing those which are pathological [36, 40, 44, 47]. Exploring the associations between these constructs in relation to healthy orthorexia and orthorexia nervosa could therefore ascertain whether healthy orthorexia uniquely is associated with more internally-driven, adaptive eating behaviors in comparison to orthorexia nervosa, and therefore identify whether these constructs are worthy of further exploration as possible protective factors against the non-pathological pursuit of a diet progressing into orthorexia nervosa.
With this in mind, the present study aimed to explore the associations between healthy orthorexia, orthorexia nervosa, intuitive eating and constructs of positive body image (body appreciation, functionality appreciation and embodiment). Based on previous findings [20, 21, 24], we hypothesized that healthy orthorexia would be positively associated with orthorexia nervosa, and that intuitive eating and indices of positive body image would be positively associated with healthy orthorexia, and inversely associated with orthorexia nervosa. Furthermore, since healthy orthorexia is proposed as an eating behavior which is distinct from orthorexia nervosa in that it is non-pathological and is positively associated with enhanced health and wellbeing [20, 21], we hypothesized that intuitive eating and indices of positive body image would be uniquely associated with healthy orthorexia after controlling for the contribution made by orthorexia nervosa. Finally, in light of the evidence supporting intuitive eating and indices of positive body image as promoting adaptive eating behaviors and reducing pathological eating behaviors [36, 40, 44, 47], we hypothesized that the relationship between healthy orthorexia and orthorexia nervosa would be moderated by intuitive eating and indices of positive body image.