Sex-specific patterns of avoidant and restrictive eating in inflammatory bowel disease: validation of the German version of the Nine Item Avoidant/Restrictive Food Intake disorder screen (NIAS)

Background Avoidant/Restrictive Food Intake Disorder (ARFID) is a possible comorbidity in patients with Inflammatory Bowel Disease (IBD). Early detection and intervention are crucial to prevent malnutrition and related complications. However, ARFID often remains undiagnosed due to its subtle presentation. Methods: This multicenter study enrolled 235 patients with IBD at German tertiary referral centers between March and September 2025. The Nine Item Avoidant/Restrictive Food Intake disorder screen (NIAS), a screening tool for ARFID, was translated into German and administered at baseline and follow-up. The validity and reliability of the NIAS German were assessed via hypothesis testing and Cronbach’s α coefficient. Results The NIAS German demonstrated excellent internal consistency (Cronbach’s α = 0.810) and test-retest reliability ( p < 0.001). A significant correlation was found between the initial and follow-up NIAS scores for all items ( p < 0.001). Furthermore, the intraclass correlation coefficient of 0.896 (95% CI: 0.846–0.931) confirmed the reliability of the German questionnaire version. Notably, women with IBD scored significantly higher on the NIAS and its subscales, indicating a greater likelihood and severity of ARFID symptoms, as screened by the NIAS (Md [IQR]: women = 13 [7–17]; men = 10 [6–15]; p = 0.007). Conclusions The German version of the NIAS demonstrated good reliability and initial evidence supporting its use as a screening instrument in German-speaking men and women with IBD. The findings of this study highlight the importance of sex-specific assessment and suggest that IBD women may be at higher risk of developing ARFID. Early detection and targeted interventions are essential to prevent malnutrition and related complications in this vulnerable population.