Biological mechanisms underlying avoidant/restrictive food intake disorder (ARFID).

Avoidant/restrictive food intake disorder (ARFID) is a complex eating disorder characterized by persistent avoidance or restriction of food intake that is not driven by concerns about body weight or shape. ARFID is characterized by an extremely low food intake and may be driven by sensory aversions to certain foods, a low interest in food, and/or traumatic experiences related to food intake, leading to avoidance. Although ARFID has a number of specific criteria and symptoms, many aspects of its diagnosis, development, and treatment remain unclear. In this narrative review, we summarize the available evidence on molecular, cellular, and neurobiological mechanisms potentially underlying the core manifestations of ARFID, including food avoidance and restriction, sensory-based food aversion, and fear of aversive consequences. The potential mechanisms discussed include altered sensory processing, dysregulation of hunger and satiety signals, conditioned taste aversion and other forms of associative learning, alterations in the microbiome-gut-brain axis, immune mechanisms, and genetic factors. Because direct evidence from ARFID populations remains limited, we also consider findings from related but diagnostically distinct conditions and phenotypes, including picky or selective eating, food neophobia, and sensory food aversion. Such findings may provide insights into mechanisms relevant to ARFID but cannot be assumed to be specific to the disorder. By integrating evidence across these biological domains, this review aims to identify potential mechanisms underlying the heterogeneous manifestations of ARFID and highlight priorities for future research.