Turkish version of the new instrument for Orthorexia Nervosa -Test of Orthorexia Nervosa (TON-17): a validity and reliability study

DOI: https://doi.org/10.21203/rs.3.rs-2313138/v1

Abstract

Background

There are several scales to evaluate orthorexia nervosa (ON), a pathological obsession, fixation or preoccupation with healthy foods. However, studies report that some of these scales have poor internal consistency and some do not have test-retest reliability, therefore new scales are needed to evaluate ON correctly. This study aims to adapt the Test of Orthorexia Nervosa-17 (TON-17) into Turkish and verify its validity and reliability.

Methods

The study included a total of 539 adults, 131 men (24.3%) and 408 women (75.7%), with a mean age of 30.2 ± 12.26 years. A reliability analysis was performed and a confirmatory factor analysis (CFA) to test its construct validity. Time invariance of the scale was examined by test-retest analysis, and its convergent validity was evaluated by a correlation analysis conducted to test relationships between the scale and other theoretically relevant instruments (EAT-26 and OBQ-9). Analyses were conducted using SPSS Version 23 and the AMOS program.

Results

The Cronbach's α internal consistency coefficient of the total scale was found to be 0.820, suggesting a strong internal consistency. The Cronbach's α values of its factors were 0.681 for the Factor 1, 0.643 for the Factor 2, and 0.726 for the Factor 3. In addition, the test-retest reliability was found as 0.868 for the total scale, suggesting an excellent reliability. The most of fit indices (CMIN/df, RMSEA, AGFI, NFI and TLI) of the scale were acceptable, and the GFI indicated a good model fit.

Conclusion

This study has shown that the Turkish version of TON-17, which is a new tool with three-factor structure to evaluate both healthy and unhealthy orthorexia, is valid and reliable scale. Studies of TON-17 on diverse cultures will contribute to the literature. Therefore, examining the validity and reliability of TON-17 in diverse cultures and populations may contribute to developing the gold standard scale for evaluating ON in future studies.

Plain English summary

There are several scales to evaluate orthorexia nervosa (ON), a pathological obsession, fixation or preoccupation with healthy foods. However, studies report that some of these scales have poor internal consistency and some do not have test-retest reliability, therefore new scales are needed to evaluate ON correctly. This study aims to adapt the Test of Orthorexia Nervosa-17 (TON-17) into Turkish and verify its validity and reliability. Turkish version of TON-17, which is a new tool with three-factor structure to evaluate both healthy and unhealthy orthorexia, is valid and reliable scale. Studies of TON-17 on diverse cultures will contribute to the literature. Therefore, examining the validity and reliability of TON-17 in diverse cultures and populations may contribute to developing the gold standard scale for evaluating ON in future studies.

Introduction

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.

Method

Participants

A total of 539 adults aged between 18–65 years, including 131 males (24.3%) and 408 females (75.7%), participated in this study. Their mean age was 30.2 ± 12.26 years. Of them, 85.5% had university or higher education, 69.2% were single, 76.1% did not smoke, 75.1% did not use alcohol, 57.0% had normal body weight, 27.3% were overweight and 7.6% were obese. All participants were Turkish citizens who could speak Turkish and lived in Turkey. A simple random sampling was used to select participants. Validity and reliability studies have reported that the sample size should be 5–10 times the number of scale items [33]. The scale used in this study consisted of 17 items, therefore we aimed to reach at least 85–170 individuals for conducting the study. A questionnaire was used as a data collection tool and sent to individuals via e-mail or WhatsApp. Those who agreed to participate in the study completed the questionnaire online after giving their consent.

Design And Procedure

To adapt the TON-17 into Turkish, a permission was obtained from Aleksandra Rogowska [9], one of the researchers who developed the test, via e-mail. The TON-17 was translated according to the guide created by Beaton et al. [34]. The original version of the questionnaire was translated into Turkish by two independent translators who could speak both Turkish and English. One of the translators was a dietitian and the other translator had no medical or clinical background. A single form was created by evaluating the translations of two translators. The Turkish version was translated into English by two native speakers and compared with the original version. This version of the questionnaire was tested on fifteen individuals to determine its understandability. A team of translators and researchers then finalized the Turkish version of the TON-17.

The reliability of the questionnaire was tested with test-retest and internal consistency analysis. To examine its test-retest reliability, the final version of the Turkish version of the TON-17 was administered to thirty volunteer adults twice, with an interval of 15 days.

The questionnaire, which was prepared with the final version of the Turkish version of the TON-17, was applied online. The questionnaire contains information about the participants’ socio-demographic characteristics (such as age, gender, educational status). Their body weight (kg) and height (cm) were based on their self-report. The Eating Attitudes Test-Short Form (EAT-26) was used to evaluate the participants’ eating behaviors [35, 36], and the Obsessive Beliefs Questionnaire-Short Form 9 (OBQ-9) to evaluate their existing obsessive disorders [37, 38].

Measurements

Test of Orthorexia Nervosa-17 (TON-17)

The Test of Orthorexia Nervosa (TON-17) is a self-report scale developed by Rogowska et al. [9] in 2021 to evaluate ON. Based on the scientific literature review and interviews with people at risk of orthorexia, it was first developed as 40 items (TON-40) to test ON, and the number of items was reduced to 17 as a result of the structural analysis. The TON-17 is considered as a useful tool to assess the risk of ON. It has three sub-factors (Control of food quality (items 1, 4, 7, 10, 13, 16); Fixation of health and healthy diet (items 2, 5, 8, 11, 14) and Disorder symptoms (items 3, 6, 9, 12, 15, 17.) and a general factor (total of 3 sub-factors). Each item was rated on a five-point Likert-like scale, indicating the degree of compliance with the sentence (1 = Strongly disagree, 2 = Disagree, 3 = Undecided, 4 = Agree, 5 = Strongly agree). The scale has no reverse scoring. A higher score is associated with greater risk of ON. The cut-off value for ON is a general factor score above 61. The internal consistency (Cronbach's α) was 0.79 for the general factor, 0.8 for the 1st factor (F1) (Control of food quality), 0.81 for the 2nd factor (F2) (Fixation on health and a healthy diet), and 0.74 for the 3rd factor (F3) (Disorder symptoms).

Eating Attitudes Test-Short Form (EAT-26)

This is a 26-question form of the Eating Attitude Test-40 developed by Garner and Garfinkel [39] in 1979, which was revised and shortened by Garner et al. [36]. The scale was adapted into Turkish by Ergüney-Okumuş and Sertel-Berk [35]. In addition to its easy-of-use and scoring, the scale provides advantages in terms of psychometric properties, economy and practicality. The Cronbach's α internal consistency coefficient of the scale was found as 0.84 in the Turkish adaptation study [35]. In this study, the Cronbach's α of the scale was determined as 0.762.

The EAT-26 is used to detect and define eating disorder behaviors in healthy individuals and to diagnose anorexia nervosa and bulimia nervosa, which are also called eating disorders. All scale items except 26th item are scored as “3 = Always, 2 = Very often, 1 = Often, 0 = Sometimes, 0 = Rarely, 0 = Never”. However, the 26th item is scored in reverse as "1 = Sometimes, 2 = Rarely, and 3 = Never", where other options get 0 points. A scale score of 20 or above indicates deterioration in eating behavior, and a higher score is associated with more evident eating disorder [35].

Obsessive Beliefs Questionnaire-Short Form- 9 (OBQ-9)

The Obsessive Beliefs Questionnaire (OBQ), which was developed by an international working group to evaluate cognitive biases specific to obsessive compulsive disorder and consisted of 87 items in its initial version, was later used as OBQ-44 with 44 items [40, 41]. Gagné et al. [37] developed a 9-item short version in 2018. The Turkish validity and reliability study of the Obsessive Beliefs Questionnaire-Short Forms was conducted in 2019 by Yorulmaz et al. [38]. The 9-item short form of the OBQ, which has 3 sub-scales (Perfectionism and Intolerance to Uncertainty (Cronbach's α = 0.75), Responsibility and Threat Perception (Cronbach's α = 0.74) and Importance and Control over Thoughts (Cronbach's α = 0.70)) was used in this study. Both the total score and the 3 sub-dimension scores of the scale can be used separately [38]. In this study, the Cronbach's α was found to be 0.762 for the total OBQ-9.

Body Mass Index (BMI)

The participants’ body weight (kg) and height (cm) values were based on their self-report. BMI was calculated by dividing the body weight in meters by the square of the height in meters (kg/m2), considering the WHO’s classification (BMI: <18.5 kg/m2 = underweight, BMI: 18.5–24.9 kg/ m2 = normal, BMI: 25.0-29.9 kg/m2 = overweight and BMI: > 30.0 kg/m2 = obese) [42].

Statistical Analysis

The data were analyzed using the IBM SPSS version 23 and the AMOS program. Descriptive statistics were used to analyze the general characteristics of the sample. Skewness and Kurtosis Tests were used to determine whether the data were normally distributed. Cronbach's alpha coefficient was calculated to determine the reliability and internal consistency of the Turkish version of TON-17, where a value above 0.60 and a value above 0.70 were considered acceptable and good fit, respectively [33]. Test-retest reliability was evaluated with the correlation coefficient calculated using the data obtained from a sub-sample of 30 participants who filled out TNO-17 twice. A confirmatory factor analysis (CFA) was performed using the AMOS program to determine the validity of the scale and to analyze the compatibility of its subscales Maximum likelihood was used to observe parameter estimation for CFA. The multiple fit indices, including CMIN/df (chi-squared goodness-of-fit), RMSEA (Root Mean Square Error of Approximation), GFI (Goodness of Fit Index), AGFI (Adjusted Goodness-of-fit Index), NFI (Normed Fit Index), and TLI (Tucker-Lewis Index) were evaluated within the scope of CFA analysis [43]. The significance level was accepted as 0.05 in all statistical analyzes.

Results

This study evaluated the validity and reliability of the Turkish version of TON-17, using data obtained from a total of 539 adults, including 131 males (24.3%) and 408 females (75.7%). The Cronbach's α internal consistency coefficient was found as 0.82 for the general factor, suggesting a strong internal consistency. The Cronbach's α was found to be 0.68 for the factor 1, 0.64 for the factor 2 and 0.72 for the factor 3. In the analysis performed to evaluate the test-retest reliability of the Turkish version of TON-17, a significant positive correlation was found for both the general factor and the sub-factors (p < 0.005) (Table 1).

Table 1

Reliability analyzes

TON-17

Item

Cronbach’s α internal consistency coefficients

Test–retest reliability

coefficients*

r

p

F1

6

0.68

0.86

< 0.01

F2

5

0.64

0.54

< 0.01

F3

6

0.72

0.78

< 0.01

General factor

17

0.82

0.86

< 0.01
*Pearson’s correlation F1: Control of food quality, F2: Fixation of health and healthy diet, F3: Disorder symptoms


Table 2 presents the fit indices of the model and Fig. 1 shows the three-factor model fit diagram. Among goodness of fit indices, CMIN/df (χ2/df) was found as 3.81, RMSEA as 0.07, GFI as 0.90, AGFI as 0.87, NFI as 0.80 and TLI as 0.81 (Table 2). On the basis of CFA, the standard factor loading of the scale varied between 0.37 and 0.58 for the Factor 1, between 0.37 and 0.60 for the Factor 2, and between 0.31 and 0.66 for the Factor 3. Accordingly, the factor loading of the TON-17, which consists of 3 factors and 17 items, were found to be at an acceptable level (Fig. 1).

Table 2

Multiple fit indexes

Index

Value

Thresholds for acceptable fit*

Thresholds for good fit*

CMIN/df

3.81

≤ 5.00

≤ 3.00

RMSEA

0.07

≤ 0.08

≤ 0.05

GFI

0.90

≥ 0.80

≥ 0.90

AGFI

0.87

≥ 0.85

≥ 0.95

NFI

0.80

≥ 0.80

≥ 0.95

TLI

0.81

≥ 0.80

≥ 0.95
CMIN/df chi-squared goodness-of-fit, RMSEA root mean square error of approximation, GFI goodness of fit index, AGFI adjusted goodness of fit index, NFI normed fit index, and TLI Tucker-Lewis index.
*Values of thresholds for acceptable and good fit [43]

 

The construct validity was examined using the Pearson/Spearman correlation coefficient between TON-17 and EAT-26 and OBQ-9. Table 3 presents the correlations of TON-17 general and sub-factors. The general factor and sub-factors (F1, F2 and F3) of TON-17 were significantly positively correlated with EAT-26 (respectively r:0.29, r:0.19, r:0.26 and r:0.25) and OBQ-9 (respectively r:0.35, r:0.23, r:0.20 and r:0.37) (p < 0.001). In addition, 7.4% of the individuals were found to have ON, considering the cut-off score for TON-17 as 61.

Table 3

Correlation of TON-17 with EAT-26 and OBQ-9 scales

Scales

Min-Max

Mean

SD

TON-17

F1

F2

F3

FG

r

p

r

p

r

p

r

p

EAT-26*

0–44

8.5

7.35

0.19

< 0.01

0.26

< 0.01

0.25

< 0.01

0.29

< 0.01

OBQ-9

                      

F1

(Perfectionism and intolerance for uncertainty)

3–21

14.0

3.56

0.17

< 0.01

0.15

< 0.01

0.22

< 0.01

0.23

< 0.01

F2

(Responsibility and threat overestimation)

3–21

13.6

3.47

0.26

< 0.01

0.22

< 0.01

0.33

< 0.01

0.34

< 0.01

F3

(Importance of and control over thoughts)

3–21

11.2

4.11

0.12

< 0.01

0.11

< 0.01

0.32

< 0.01

0.24

< 0.01

Total score

14–63

38.8

8.73

0.23

< 0.01

0.20

< 0.01

0.37

< 0.01

0.35

< 0.01

TON-17

                      

F1

(Control of food quality)

6–30

17.9

3.92

    

0.68

< 0.01

0.41

< 0.01

0.87

< 0.01

F2

(Fixation of health and healthy diet)

6–25

17.0

2.90

        

0.28

< 0.01

0.78

< 0.01

F3

(Disorder symptoms)

6–28

13.3

3.84

            

0.73

< 0.01

General factor

20–74

48.2

8.54

                
*Spearman correlation, others Pearson’s correlation. EAT-26: The Eating Attitudes Test-26; OBQ-9: Obsessive Beliefs Questionnaire-Short Form 9; TON-17: Test of Orthorexia Nervosa-17

DISCUSSION

This study was conducted to determine the Turkish validity and reliability of the TON-17 [9], a scale used to determine the risk of ON. The relationship between eating behavior and obsessive behavior was analyzed by the TON-17. Similar to the original study (Cronbach's α was found as 0.79 for the general factor), the reliability analysis of the Turkish version of the TON-17 suggested good internal consistency (Cronbach's α 0.82) for the general factor. The Cronbach's α values for the three factors of the scale were lower than those in the original study, but at an acceptable level (0.68, 0.64 and 0.72 for F1, F2 and F3, respectively). The test-retest reliability was found as 0.868 for the general factor, suggesting an excellent reliability. Most of the fit indices (CMIN/df, RMSEA, AGFI, NFI and TLI) obtained by CFA analysis were found to be at acceptable or good (GFI) level. Accordingly, the TON-17 is considered a valid and reliable tool to determine the risk of ON in Turkish people, and it is associated with both eating disturbance and obsessive behavior.

ON is characterized by consuming healthy foods and focusing on their content and quality [31] and is briefly defined as an obsession with healthy eating [11]. This behavior may include an unbalanced diet due to beliefs about the “purity” of food, strict avoidance of unhealthy foods, feelings of guilt and anxiety after eating violations, or intolerance to other people’s food beliefs [17, 31]. Extreme orthorexic behaviors may deteriorate physical health due to malnutrition and cause social and academic failures due to obsessive thoughts and behaviors focused on beliefs about healthy eating [17].

In the literature, diverse scales (BOT, ORTO-15, EHQ, DOS, TOS, BOS, and ONI) are used to evaluate ON [3], and their positive and negative aspects are discussed [3, 4, 17]. A decrease in the total score in ORTO-15, one of the most frequently used scales in the literature, indicates higher orthorexic behavior [26]. While the individuals with the lowest score was defined as the group with ON, but some of them with the lowest score were observed to have healthy eating behaviors and normal personality and this is not discussed by researchers [3, 26]. In the following years, several versions of ORTO-15 with different item number, factor number and cut-off scores were developed [44–47]. Therefore, the usability of ORTO-15 has been questioned by many studies due to the high frequency of ON in the groups studied, the lack of information about how the items are created, and the lack of a clear validated tool [3, 4, 17]. The use of ORTO-15 is considered dubious due to these limitations, and its use is not recommended, although it is popular. Although BOT has not been validated and is not psychometrically valid, it is used as a diagnostic tool [3]. EHQ consists of 21 items with three factors independent of ORTO-15 [23]. However, the structure of the factors has changed and the methods for interpreting the results are different in other versions of this scale [47, 48]. DOS [22] has two different versions with 21 and 10 items. There are 3 subscales in the long version and 2 subscales in the short version. The presence of different number of subscales is thought-provoking about its use. BOS was developed based on the diagnostic criteria of Dunn and Bratman [29]. There is no study to evaluate ON by the scale, which has English and Spanish versions. The Teruel Orthorexia Scale (TOS) [28] was developed in accordance with the ON concept proposed by Bratman [7]. It has a two-factor structure: healthy eating and ON pathological domain [28]. ONI [30] is a scale based on EHQ and DOS. Some of its items were developed to effectively distinguish between healthy nutrition and pathological behavior. The ONI is considered to be the first diagnostic tool for ON that can be used to assess physical impairment.

Considering the literature reviews, there is no gold standard in determining the risk of ON. Future studies are important for reaching the gold standard in determining the risk of ON [9]. In this regard, the validity and reliability studies of the TON-17 in different societies will contribute to the literature. The TON-17 scale was developed based on the recommendations of Valente et al. [32] based on qualitative methods (e.g. interviews) and reconceptualization of ON using cutting-edge technology. In addition, statistical techniques such as EFA, CFA and CCA supported the structural construction of TON-17. TON-17 consists of three sub-factors: Control of food quality, Fixation of health and healthy diet, and Disorder symptoms. This structure with three subscales for ON has been used previously in DOS, EHQ, and ORTO-15 [2]. However, it has been stated that the development of ON can be examined in two stages, namely, healthy orthorexia, which is interested in healthy nutrition without pathological features, and ON, which focuses on healthy nutrition obsessively [7]. In the TON-17, both F1 and F2 sub-factors are associated with healthy orthorexia, while F3 is associated with unhealthy orthorexia [9].

Due to the lack of standardized diagnostic tools, there is a large difference in the prevalence rates of ON in the literature, ranging from 0–97% [49, 50]. The prevalence of ON varies by country of study, participant profile, and the tool used to assess ON in the study. While the prevalence of ON was 6.9% [18] in one study using ORTO-15, it was 75.2% in another study [51]. In studies using BOT, the prevalence of ON varies between 0.1% and 68.2% [52, 53]. The prevalence of ON was found as 5.5% in the study of Rogowska et al. [9]. Also, the prevalence of ON was found to be 7.5% in the present study. Niedzielski et al. [3] have reported that there is no reliable data on the prevalence of ON and that there are differences in the frequency of ON depending on the diverse cut-off scores and tools used in the current studies. The authors have stated that it is difficult to determine the prevalence of ON and that the tendency to ON may be high in some groups. They have also reported that the use of ORTO-15 to diagnose ON should be questioned due to the high rate of false positive results [3]. Therefore, further studies are needed in different cultures and populations.

Future studies of TON-17 on diverse cultures will contribute to the literature. Our study found that the Turkish version of TON-17 has construct validity and reliability (Cronbach’s α: 0.82), and determined a positive correlation between EAT-26, OBQ-9 and TON-17 scores (r:0.29 and r:0.23, p < 0.01, respectively). Similarly, previous studies [10, 32] have found a relationship between ON and eating behavior. Another study reported obsessive behaviors in ON [4]. It is considered that TON-17 will be an important tool in determining the risk of ON, since it provides information about both healthy and unhealthy orthorexia and is a valid and reliable tool.

Conclusion

Although some tools have been developed for ON assessment, there is no method yet to be considered as the gold standard. This study has shown the Turkish validity and reliability of the TON-17, a new tool with three-factor structure to evaluate both healthy and unhealthy orthorexia. This scale will contribute to the literature, allowing future studies to better examine the prevalence, risk and diagnosis of ON.

Abbreviations

ON: Orthorexia Nervosa; TON-17: Test of Orthorexia Nervosa-17; CFA: Confirmatory Factor Analysis; EAT-26: The Eating Attitudes Test-26; OBQ-9: Obsessive Beliefs Questionnaire-Short Form 9; SPSS: Statistical Package for the Social Sciences; CMIN/df : Chi-squared Goodness-of-Fit; RMSEA: Root Mean Square Error of Approximation; AGFI: Adjusted Goodness-of-Fit Index; NFI: Normed Fit Index; TLI: Tucker–Lewis Index; ICD-11: International Classification of Diseases; DSM-5: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; ARFID: Avoidance/restrictive food intake disorder; OCD: Obsessive Compulsive Disorder; BOT: Bratman Orthorexia Test; ORTO-15: Orthorexia Nervosa Rating Scale-15 (ORTO-15); BISQ: Body Image Screening Questionnaire; B-ORA: Burda Orthorexia Risk Assessment; DOS: Düsseldorf Orthorexia Scale; EHQ: Eating Habits Questionnaire; EHQ-R: Revised Eating Habits Questionnaire; ONS: Orthorexia Nervosa Scale; TOS: Teruel Orthorexia Scale; BOS: Barcelona Orthorexia Scale; ONI: Orthorexia Nervosa Inventory; GFI: Goodness of Fit Index.

Declarations

Acknowledgments

We thank all participants for their time and contributions.

Author Contributors

EY contributed to the design, data collection, data analysis and preparation of the paper, and FA contributed to the data collection, and preparation of the paper. All the authors read and approved the final manuscript.

Funding

No funding was received for this study.

Conflict of Interest

All authors declare that they have no conflicts of interest.

Availability of data and materials

The datasets used during the present study can be obtained from the corresponding author on reasonable request.

Ethical approval and consent to participate

All procedures performed in the present study were in accordance with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Ethical approval was obtained from the Ethics Committee at Gazi University (Code No: 2022-072). Submitting the form online was considered equivalent to obtaining written informed consent.

Consent for publication

Not applicable.

Competing interests

There are no competing interests in this article

References

  1. Bratman S, Knight D. Health food junkie. Yoga J. 1997;136:42-50.
  2. Opitz M-C, Newman E, Mellado ASAV, Robertson MD, Sharpe H. The psychometric properties of orthorexia nervosa assessment scales: a systematic review and reliability generalization. Appetite. 2020;155:104797.
  3. Niedzielski A, Kaźmierczak-Wojtaś N. Prevalence of orthorexia nervosa and its diagnostic tools—A literature review. Int J Environ Res Public Health. 2021;18(10):5488.
  4. Koven NS, Abry AW. The clinical basis of orthorexia nervosa: emerging perspectives. Neuropsychiatr Dis Treat. 2015;11:385-94.
  5. Sánchez FG, Rial BR. Orthorexia nervosa. A new eating behavior disorder. Actas Esp Psiquiatr. 2005;33(1):66-8.
  6. Koven NS, Senbonmatsu R. A neuropsychological evaluation of orthorexia nervosa. Neuropsychiatr Dis Treat. 2013;3:214-22.
  7. Bratman S. Orthorexia vs. theories of healthy eating. Eat Weight Disord. 2017;22(3):381-85.
  8. American Psychiatric Association. "Ruhsal bozuklukların tanısal ve sayımsal elkitabı, translated from the fifth edition DSM-5 handbook of differential diagnosis. Köroğlu E. (Translation ed.), Ankara: Hekimler Yayın Birliği; 2013.
  9. Rogowska AM, Kwaśnicka A, Ochnik D. Development and validation of the test of orthorexia nervosa (TON-17). J Clin Med. 2021;10(8):1637.
  10. Varga M, Dukay-Szabó S, Túry F, van Furth Eric F. Evidence and gaps in the literature on orthorexia nervosa. Eat Weight Disord. 2013;18(2):103-11.
  11. Cena H, Barthels F, Cuzzolaro M, Bratman S, Brytek-Matera A, Dunn T, Varga M, Missbach B, Donini LM. Definition and diagnostic criteria for orthorexia nervosa: a narrative review of the literature. Eat Weight Disord. 2019; 24(2):209-46.
  12. Zagaria A, Vacca M, Cerolini S, Ballesio A, Lombardo C. Associations between orthorexia, disordered eating, and obsessive–compulsive symptoms: A systematic review and meta‐analysis. Int J Eat Disord. 2022;55(3):295-12.
  13. Asil E, Sürücüoğlu MS. Orthorexia nervosa in Turkish dietitians. Ecol Food Nutr. 2015;54(4):303-313.
  14. Garipoglu G, Arslan M, Ozturk-Andac S. Determining orthorexia nervosa tendencies of female students studying in the Department of Nutrition and Dietetics. J Istanbul Sabahattin Zaim Univ Nat Sci Inst. 2019;1(3):23-7.
  15. Sanlier N, Yassibas E, Bilici S, Sahin G, Celik B. Does the rise in eating disorders lead to increasing risk of orthorexia nervosa? Correlations with gender, education, and body mass index. Ecol Food Nutr. 2016;55(3):266-78.
  16. Missbach B, Dunn TM, König JS. We need new tools to assess orthorexia nervosa. A commentary on “prevalence of orthorexia nervosa among college students based on Bratman’s test and associated tendencies”. Appetite. 2017;108(1):521-24.
  17. Dunn TM, Bratman S. On orthorexia nervosa: A review of the literature and proposed diagnostic criteria. Eat Behav. 2016;21:11-17.
  18. Dunn TM, Gibbs J, Whitney N, Starosta A. Prevalence of orthorexia nervosa is less than 1%: data from a US sample. Eat Weight Disord. 2017;22(1):185-192.
  19. Jenaro C, Flores N, Bermejo BG, Cruz M. Cuestionario de imagen corporal para la detección temprana de trastornos de la conducta alimentaria. Acción Psicológica 2011;8(8):7-20.
  20. Burda L. Development and Validation of an inventory measuring dietary Attitudes of healthy Eating and Orthorexia nervosa, Texas A&M University, PhD Thesis. USA; 2018.
  21. Bratman S, Knight D. Health food junkies: Orthorexia nervosa: Overcoming the obsession with healthful eating. National Geographic Books; 2004.
  22. Barthels F, Meyer F, Pietrowsky R. Duesseldorf Orthorexia Scale construction and evaluation of a questionnaire measuring orthorexic eating behavior. Zeitschrift Fur Klinische Psychologie Und Psychotherapie 2015;44(2):97-105.
  23. Gleaves DH, Graham EC, Ambwani S. Measuring “orthorexia”: development of the eating habits questionnaire. Int J Educ Psychol Assess. 2013;12(2):1-18.
  24. Glen K, Gleaves D. Development and validation of the Eating Habits Questionnaire-Revised (EHQ-R). University of South Australia Adelaide, PhD Thesis. Australia; 2018.
  25. Kramer ME. Development of a scale to measure orthorexia nervosa, Colorado State University, PhD Thesis. USA; 2016.
  26. Donini LM, Marsili D, Graziani MP, Imbriale M, Cannella C. Orthorexia nervosa: validation of a diagnosis questionnaire. Eat Weight Disord. 2005;10(2):e28-e32.
  27. Carrero T, Cotto LP, Rodríguez-Gómez J. Construcción y Validación de una Escala para Tamizar Ortorexia: Primer estudio piloto en Puerto Rico. Boletin de la Asociacion Medica de Puerto Rico. 2016;108(2):89-95.
  28. Barrada JR, Roncero M. Bidimensional structure of the orthorexia: development and initial validation of a new instrument. Anales De Psicología/Annals of Psychology 2018;34(2):283-291.
  29. Bauer SM, Fusté A, Andrés A, Saldaña C. The Barcelona Orthorexia Scale (BOS): development process using the Delphi method. Eat Weight Disord. 2019;24(2):247-255.
  30. Oberle CD, De Nadai AS, Madrid AL: Orthorexia Nervosa Inventory (ONI): development and validation of a new measure of orthorexic symptomatology. Eat Weight Disord. 2021;26(2):609-622.
  31. Meule A, Holzapfel C, Brandl B, Greetfeld M, Hessler-Kaufmann JB, Skurk T, Quadflieg N, Schlegl S, Hauner H, Voderholzer U. Measuring orthorexia nervosa: a comparison of four self-report questionnaires. Appetite. 2020;146:104512.
  32. Valente M, Syurina EV, Donini LM: Shedding light upon various tools to assess orthorexia nervosa: a critical literature review with a systematic search. Eat Weight Disord. 2019;24(4):671-682.
  33. Nunnally J, Bernstein I. Psychometric Theory, 3rd edn. MacGraw-Hill, New York; 1994.
  34. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine. 2000;25(24):3186-3191.
  35. Ergüney-Okumuş FE, Sertel- Berk Ö.Yeme Tutum Testi Kısa Formunun (YTT-26) Üniversite Örnekleminde Türkçeye Uyarlanması ve Psikometrik Özelliklerinin Değerlendirilmesi. Psikoloji Çalışmaları. 2020;40 (1): 57-78.
  36. Garner DM, Olmsted MP, Bohr Y, Garfinkel PE. The eating attitudes test: psychometric features and clinical correlates. Psychol Med.1982;12(4):871-878.
  37. Gagné JP, Van Kirk N, Hernandez‐Vallant A, Potluri, S, Krompinger JW, Cattie JE, Garner LE, Crosby JM, Brennan BP, Elias A. Validating an abbreviated version of the Obsessive Beliefs Questionnaire. J Clin Psychol. 2018;74(10):1791-1807.
  38. Yorulmaz O, Güngör D, Gökdağ C. The Obsessive Beliefs Questionnaire: Adaptation of Its Short Forms to the Turkish and Examination of Their Psychometric Properties. Turkish Journal of Psychiatry 2019;30(3):191-199.
  39. Garner DM, Garfinkel PE.The Eating Attitudes Test: An index of the symptoms of anorexia nervosa. Psychol Med. 1979;9(2):273-79.
  40. Obsessive Compulsive Cognitions Working Group. Psychometric validation of the obsessive beliefs questionnaire and the interpretation of intrusions inventory: Part I. Behav Res Ther. 2003;41(8):863-78.
  41. Obsessive Compulsive Cognitions Working Group. Psychometric validation of the obsessive belief questionnaire and interpretation of intrusions inventory: Part 2: Factor analyses and testing of a brief version. Behav Res Ther. 2005;43(11):1527-42.
  42. Body mass index-BMI. Available from: https://www.euro.who.int/en/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi
  43. Simon D, Kriston L, Loh A, Spies C, Scheibler F, Wills C, Härter M. Confirmatory factor analysis and recommendations for improvement of the Autonomy‐Preference‐Index (API). Health Expect. 2010;13(3):234-243.
  44. Arusoğlu G, Kabakçi E, Köksal G,Merdol TK. Orthorexia Nervosa and Adaptation of ORTO-11 into Turkish. Turk Psikiyatri Derg 2008;19(3).
  45. Babeau C LCT, Julien-Sweerts S, Brochenin A, Donini LM, Fouques D. : Structural validation of the ORTO-12-FR questionnaire among a French sample as a first attempt to assess orthorexia nervosa in France. Eat Weight Disord 2020;25:1771-1778.
  46. Moller S AP, Knowles SR. : Confirmatory factor analyses of the ORTO 15-, 11-and 9-item scales and recommendations for suggested cut-off scores. Eat Weight Disord. 2019;24:21-28.
  47. Oberle CD SR, Hughes EM.: Orthorexia nervosa: Assessment and correlates with gender, BMI, and personality. Appetite 2017;108:303-310.
  48. Halim ZM DK, Kemps E, Prichard I.: Orthorexia nervosa: Examining the Eating Habits Questionnaire’s reliability and validity, and its links to dietary adequacy among adult women. Public Health Nutr 2020;23:1684-1692.
  49. Barthels F MR, Schüth T, Friederich H-C, Pietrowsky R. : Orthorexic eating behavior in patients with somatoform disorders. Eat Weight Disord. 202;26:135-143.
  50. Zańko A MA, Plyton T, Anud S, Smarkusz-Zarzecka J, Pietraszewska B, Milewski R.: How Does Orthorexia Nervosa Assessment Tools Can Differ–Comparison of Two Questionnaires: BOT and ORTO-15. Stud Log Gram Rhetor 2019;60:33-48.
  51. Haddad C OS, Akel M, Honein K, Akiki M, Azar J, Hallit S.: Correlates of orthorexia nervosa among a representative sample of the Lebanese population. Eat Weight Disord. 2019;24:481-493.
  52. Brzęk A ZKPP: A study on the relationship between orthorexia and vegetarianism using the BOT (Bratman Test for Orthorexia). Psychiatr Pol 2017;51:1133-1144.
  53. Grammatikopoulou MG GK, Markaki A, Theodoridis X, Tsakiri V, Mavridis P, Dardavessis T, Chourdakis M.: Food addiction, orthorexia, and food-related stress among dietetics students. Eat Weight Disord. 2018;23:459-67.