Validity and reliability of the Dietary Rules Inventory (DRI)

BACKGROUND: Dietary rules are common in patients with eating disorders, and according to transdiagnostic cognitive behavioural theory for eating disorders, represent a key behaviour maintaining eating-disorder psychopathology. The aim of this study was to describe the design and validation of the Dietary Rules Inventory (DRI), a new self-report questionnaire that assesses dietary rules in patients with eating disorders.METHODS: A transdiagnostic sample of 320 patients with eating disorders, as well as 95 patients with obesity and 122 healthy controls were recruited. Patients with eating disorders also completed the Dutch Eating Behaviour Questionnaire (DEBQ), the Eating Disorder Examination Questionnaire, the Brief Symptoms Inventory and the Clinical Impairment Assessment. Dietary rules were rated on a continuous Likert-type scale (0-4), rating how often (from never to always) they had been applied over the previous 28days.RESULTS: DRI scores were significantly higher in patients with eating disorders than in patients with obesity and healthy controls. Principal factor analysis identified that 55.8% of the variance was accounted for by four factors, namely 'what to eat', 'social eating', 'when and how much to eat' and 'caloric level'. Both global score and subscales demonstrated high internal and test-retest reliability. The DRI global score was significantly correlated with the DEBQ 'restrained eating' subscale, as well as eating-disorder and general psychopathology and clinical impairment scores, demonstrating good convergent validity.CONCLUSIONS: These findings suggest that the DRI is a valid self-report questionnaire that may provide important clinical information regarding the dietary rules underlying dietary restraint in patients with eating disorders.LEVEL OF EVIDENCE: V, descriptive study.