Orthorexia Nervosa (ON) was first defined by Bratman in 1997 as “unhealthy obsession with healthy eating” [1]. In the current literature, ON is defined as “pathological obsession, fixation or preoccupation with healthy foods” [2]. ON is characterized by excessive concentration on food quality, food preparation, and nutrition [3]. ON has several symptoms, including avoidance of food additives such as preservatives, colors, flavorings, pesticides, excessive fat, sugar and salt, or genetically modified organism [3, 4]. In addition, individuals with ON may be obsessed with cooking methods and tools in the food preparation process, and may feel guilt and fear when they go beyond their norms in this process [1, 5]. Thoughts on healthy nutrition, food preparation, and labeling of foods can negatively affect both quality of life and social life in individuals with ON [6]. Bratman [7] has argued that the development of ON can be examined in two stages: healthy orthorexia, which is interested in healthy nutrition without pathological features, and unhealthy orthorexia, which focuses on healthy nutrition obsessively.
ON is not yet considered a psychiatric eating disorder, and it is not included in the eleventh revision of the International Classification of Diseases (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) [8]. There is no consensus on whether ON should be classified as an eating disorder syndrome or a variance of other syndromes (such as anorexia nervosa, avoidance/restrictive food intake disorder (ARFID), obsessive-compulsive disorder (OCD), obsessive-compulsive personality disorder, somatic symptom disorder) [9]. Although there are several definitions of ON and diverse tools for its diagnosis, there is no accepted ON definition and standardized diagnostic criteria [3, 10]. Cena et al. [11] discusses not only the similarities and differences between ON and eating disorders, but also the similarities and differences between ON and OCD. Specifically, the authors emphasize rigidity, perfectionism, and other obsessive-compulsive traits as their common features, while the only difference between is that OCD symptoms are related to healthy eating in ON. In their meta-analysis, Zagaria et al. [12] have reported that ON symptoms are more associated with eating disorders compared to OCD, and therefore ON can be included in the DSM classification as an emerging eating disorder.
The first studies on ON were conducted using the Bratman Orthorexia Test (BOT) and the Orthorexia Nervosa Rating Scale-15 (ORTO-15) [9]. In Turkey, studies have been conducted to determine the ON tendency by using the ORTO-11, a shorter version of the ORTO-15 [13–15]. However, as the results of these studies may be biased or misleading, these two tools are criticized for their lack of validity and reliability [16]. Depending on the research scale and country, the prevalence of ON is more common (35–89%) among artists, health professionals, nutrition students, dietitians, and athletes, but varies widely from 1–89% [10, 17]. Dunn et al. [18] suggested that the frequency of ON was found high in most studies, since the assessment tools they used did not distinguish individuals with ON from individuals with healthy eating habits.
A recent systematic review reported a total of 10 different scales to evaluate ON [2], including Body Image Screening Questionnaire (BISQ) [19], Burda Orthorexia Risk Assessment (B-ORA) [20], Bratman's test (Orthorexia self-test— BOT) [21], Düsseldorf Orthorexia Scale (DOS) [22], Eating Habits Questionnaire (EHQ) [23], Revised Eating Habits Questionnaire (EHQ-R) [24], Orthorexia Nervosa Scale (ONS) [25], ORTO-15 Questionnaire [26], Scale to Measure Orthorexia in Puerto Rican Men and Women [27] and Teruel Orthorexia Scale (TOS) [28]. In addition, recent studies with Barcelona Orthorexia Scale (BOS) [29] and Orthorexia Nervosa Inventory (ONI) [30] are also included in the literature. Among these scales, BISQ, ORTO-15, BOT and ONS have low internal consistency, and most of them (such as BISQ, BOT, ONS) did not have test-retest reliability, some (DOS, TOS) has challenging preliminary diagnostic criteria, and some (EHQ-R, ONS, B-ORA) need further evaluation [2]. Meule et al. [31] reported good internal reliability for BOT, EHQ, and DOS and unacceptable internal reliability for ORTO-15. In addition, the authors stated that BOT, EHQ, and DOS were highly correlated with each other and moderately correlated with ORTO-15 [31].
Valente et al. [32] conducted a critical literature review about existing scales on ON and suggested that ON should be reconceptualized, relevant qualitative data collection techniques should be determined to gain insight into its diagnosis, and a new scale should be developed its assessment. In line with the recommendations of Valente et al.[32], Rogowska et al. [9] developed a new scale for ON in 2021. The Test of Orthorexia Nervosa-40 (TON-40), which was initially included 40 items, was reduced to 17 items (Test of Orthorexia Nervosa-17, TON-17) as a result of structural analysis. The TON-17 and its factors had good psychometric properties, stability, reliability and construct validity. It consists of 3 factors: Control of food quality, Fixation of health and healthy diet, and Disorder symptoms [9]. The TON-17 differs from other scales due to some features. In particular, current scales do not assess the development of ON from a healthy diet to a pathological diet. As in Bratman's theory [7], ON has two stages. In the first stage, people decide to eat healthy. Their interest in healthy eating does not always become pathological. However, a further progress occurs when a person adopts irrational, unscientific, or non-standard dietary ideas. In the second stage, there is a rapid increase in obsessive thinking, compulsive behavior, self-punishment and restrictions [7, 9].
In Turkey, the ORTO-11 scale, a short version of ORTO-15, is used in studies to determine ON tendency. However, there are contradictions in the results of these studies in terms of validity and reliability with a suggestion of high ON frequencies. This study will contribute to the literature by evaluating the Turkish validity and reliability of TON-17, which was developed in line with the current literature.