Avoidant/Restrictive Food Intake Disorder Symptoms Across Body Mass Index Strata: Measurement Invariance and Symptom Differences

Objective Avoidant/restrictive food intake disorder (ARFID) occurs across the lifespan and body mass index (BMI) spectrum, yet little is known about how ARFID presents across BMI strata in adults. This study evaluated measurement invariance of the Nine‐Item ARFID Screen (NIAS) across BMI groups and examined differences in ARFID symptoms and clinical features. Method Adults ( N = 3118) from the ARFID Genes and Environment (ARFID‐GEN) study completed self‐report measures, including the NIAS and the Pica, ARFID, and Rumination Disorder Interview ARFID Questionnaire. Structural equation and generalized linear models evaluated NIAS measurement invariance across BMI groups and assessed group differences in ARFID symptom dimensions and clinical features. Results Almost half of the sample presented with overweight or obesity. Nutritional deficiency was more often reported among higher BMI groups, and psychosocial impairment did not differ significantly across strata. Measurement invariance was supported for several BMI comparisons, including normal weight versus overweight, normal weight versus obesity, and overweight versus obesity. In pairwise comparisons between invariant groups, picky eating was elevated in both underweight and obesity groups, while low appetite and fear were higher among adults with underweight. Discussion Findings indicate that ARFID occurs across the adult BMI spectrum and that NIAS scores can be compared across most BMI groups, apart from highly discrepant groups. Results highlight that ARFID dimensions vary across BMI groups and that ARFID is not limited to traditionally low‐weight presentations. Continued research is needed to characterize ARFID across the BMI spectrum, particularly among higher‐BMI adults, who represent a meaningful proportion of those affected.