Mechanisms of Avoidant/Restrictive Food Intake Disorder (ARFID)
ARFID is characterized by three primary neurobiological mechanisms: sensory sensitivity, lack of interest in eating/low appetite, and fear of aversive consequences, which correspond to abnormalities in sensory perception, homeostatic appetite, and negative valence systems respectively. 1
Core Neurobiological Mechanisms
1. Sensory-Based Avoidance
- Neurobiological basis: Abnormalities in sensory perception systems 1
- Manifests as hypersensitivity to food textures, tastes, smells, or appearance
- Patients often reject foods based on specific sensory characteristics
- May be associated with sensory processing disorders or autism spectrum conditions 2
2. Lack of Interest in Food/Eating
- Neurobiological basis: Abnormalities in homeostatic appetite regulation 1
- Presents as apparent lack of hunger, disinterest in food, or easily feeling full
- May involve disruption in hunger/satiety signaling pathways
- Often results in inadequate caloric intake despite absence of body image concerns 2
3. Fear-Based Avoidance
- Neurobiological basis: Abnormalities in negative valence systems 1
- Characterized by fear of choking, vomiting, gastrointestinal distress, or allergic reactions
- Often triggered by a specific adverse event related to eating
- Frequently comorbid with anxiety disorders 2
Contributing Factors and Comorbidities
Medical and Gastrointestinal Factors
- Significant overlap with gastrointestinal disorders and functional dyspepsia 2
- Comorbidity with disorders of gut-brain interaction (DGBI) 2
- Association with hypermobility disorders/hypermobile Ehlers-Danlos Syndrome 2
- Chronic gastrointestinal symptoms may reinforce fear-based avoidance patterns
Psychological Factors
- High comorbidity with anxiety disorders 2
- Possible relationship with obsessive-compulsive traits
- Cognitive rigidity may contribute to difficulty with dietary flexibility
- Early feeding difficulties or traumatic feeding experiences may establish avoidance patterns
Clinical Consequences
Nutritional Impact
- Significant weight loss or failure to gain expected weight 2
- Growth stunting in children 2
- Nutritional deficiencies due to limited dietary variety 2
- Dependence on nutritional supplements 2
Psychosocial Impact
- Impaired social functioning due to inability to participate in food-related activities 2
- Family stress and conflict around mealtimes
- Potential for social isolation
- Interference with developmental milestones in children 3
Maintaining Mechanisms
- Negative reinforcement: Avoidance behaviors reduce anxiety or discomfort
- Learned associations: Pairing of foods with negative experiences strengthens avoidance
- Physiological adaptation: Reduced food intake leads to decreased gastric capacity and early satiety
- Environmental accommodation: Family members may inadvertently reinforce restrictive patterns
Clinical Implications
- ARFID requires a multidimensional assessment targeting the specific presentation pattern(s) 2
- Treatment approaches should be tailored to the underlying mechanism(s) 2, 3
- Graded exposure therapy in a cognitive-behavioral framework is recommended rather than reinforcing restriction 2
- Avoid parenteral nutrition except in life-threatening cases as it may reinforce avoidance 4, 2
Pitfalls in Management
- Misdiagnosis by failing to distinguish ARFID from anorexia nervosa 2
- Overlooking comorbid anxiety disorders or gastrointestinal conditions 2
- Reinforcing avoidance through unnecessary elimination diets 2
- Inappropriate use of supplements leading to dependence without addressing underlying factors 2
Understanding these neurobiological mechanisms is essential for accurate diagnosis and effective treatment planning for individuals with ARFID.