Italian adaptation of the Düsseldorf Orthorexia Scale (I-DOS): psychometric properties and prevalence of orthorexia nervosa among an Italian sample

Purpose: Orthorexia Nervosa (ON) is described as an extreme level of preoccupation around healthy eating, accompanied by restrictive eating behaviors. During the years, different assessment instruments have been developed. The aim of the study is to adapt into Italian the Düsseldorf Orthorexia Scale (I-DOS) and to test its psychometric properties. Method: A total sample of 422 volunteer university students (mean age = 20.70 ± 3.44, women 71.8%) completed a group of self-report questionnaires in large group sessions during their lecture time. The scales assessed ON (the I-DOS and the Orhto-15), disordered eating (Disordered Eating Questionnaire, DEQ), depressive symptoms (Beck Depression Inventory-II, BDI-II), obsessive and compulsive symptoms (Obsessive Compulsive Inventory-Revised, OCI-R), and self-reported height and weight. Results: The fit of the unidimensional structure and reliability of the I-DOS was tested trough Confirmatory Factor Analysis (CFA) as well as its criterion validity computing correlation coefficients among Ortho-15, DEQ, BDI-II, OCI-R, BMI. Analyses confirmed the unidimensional structure of the I-DOS with acceptable or great fit indices (CFI = 0.984; TLI = 0.978; SRMR = 0.043; RMSEA = 0.076) and the strong internal consistency (α = 0.888). The correlations path supported the criterion validity of the scale. The estimated total prevalence of both ON and ON risk was 8.1%. Conclusions: This 10-item scale appears to be a valid and reliable measure to assess orthorexic behaviors and attitudes. Level of evidence: Level V, descriptive cross-sectional study.