When Eating Right, Is Measured Wrong! A Validation and Critical Examination of the ORTO-15 Questionnaire in German

Abstract

The characteristic trait of individuals developing a pathological obsession and preoccupation with healthy foods and a restrictive and avoidant eating behavior is described as orthorexia nervosa (ON). For ON, neither universal diagnosis criteria nor valid tools for large-scale epidemiologic assessment are available in the literature. The aim of the current study is to analyze the psychometric properties of a translated German version of the ORTO-15 questionnaire. The German version of the ORTO-15, a eating behavior and dieting habits questionnaire were completed by 1029 German-speaking participants (74.6% female) aged between 19 and 70 years (M = 31.21 ± 10.43 years). Our results showed that after confirmatory factor analysis, the best fitting model of the original version is a single-factor structure (9-item shortened version: ORTO-9-GE). The final model showed only moderate internal consistency (Cronbach's alpha = .67), even after omitting 40% of the original question. A total of 69.1% participants showed orthorectic tendencies. Orthorectic tendencies are associated with special eating behavior features (dieting frequency, vegetarian and vegan diet). Education level did not influence ON tendency and nutritional students did not show higher ON tendency compared to students from other disciplines. This study is the first attempt to translate and to evaluate the psychometric properties of a German version of the ORTO-15 questionnaire. The ORTO-9-GE questionnaire, however, is only a mediocre tool for assessing orthorectic tendencies in individuals and shows moderate reliability and internal consistency. Our research suggests, that future studies are needed to provide more reliable and valid assessment tools to investigate orthorexia nervosa.

Fig 1. ORTO-15 as originally hypothesized by Donini and colleagues (3-factor structure).

The displayed values are unstandardized regression weights from the study sample in the original 3-factor structure. Squares represent items, oval circles represent factors, squares represent questionnaire items and small circles represent error terms.

Fig 2. ORTO-9-GE factor structure after item omission and model fit (1-factor structure).

The displayed values are unstandardized regression weights from the study sample after model fit and correlation of error terms: 3/4, 5/6. Squares represent items, oval circles represent factors, squares represent questionnaire items and small circles represent error terms.

Fig 3. ORTO-9-GE scores associated with dieting style.

ORTO-9-GE scores as a function of dieting style. Participants dieting style defined as either vegan, vegetarian or having a mixed diet. Lower ORTO-9-GE scores indicate higher orthorectic tendencies.

Fig 4. ORTO-9-GE scores associated with dieting experience.

ORTO-9-GE scores as a function of dieting experience (range: no dieting experience to > 6 diets). Lower ORTO-9-GE scores indicate higher orthorectic tendencies. Error bars indicate standard errors of the means.

Fig 5. ORTO-9-GE scores associated with lifetime weight changes.

ORTO-9-GE scores as a function of lifetime weight changes (range from 1-5kg to > 40kg lifetime weight change). Lower ORTO-9-GE scores indicate higher orthorectic tendencies. Error bars indicate standard errors of the means.