Food Restriction in Anorexia Nervosa in the Light of Modern Learning Theory: A Narrative Review

Testing the role of associative learning in evidence-based treatments for anorexia nervosa

Treatments for anorexia nervosa (AN) remain ineffective for many patients. Processes that can account for differential treatment outcomes remain mostly unknown. We propose that the field test the role of associative learning in current psychological treatments. We hold that this line of research could yield actionable information for understanding non-response and improving long-term outcomes. To make this argument, we define associative learning and outline its proposed role in understanding psychiatric disorders and their treatment. We then briefly review data exploring associative learning in AN. We argue that associative learning processes are implicitly implicated in existing treatments; by this rationale, baseline differences in learning may interfere with treatment response. Finally, we outline future research to test our hypotheses. Altogether, future research aimed at better understanding how associative learning may contribute to AN symptom persistence has the potential to inform novel directions in intervention research. PUBLIC SIGNIFICANCE: There is a pressing need to improve outcomes in treatments for anorexia nervosa (AN). We propose that individual differences in associative learning-the ability to form and update associations between cues, contexts, behaviors, and outcomes-may account for differential response to existing treatments. Undertaking this research could provide an understanding of how current treatments work and inform new approaches for those who may be at risk of poor outcomes.

Habits and Persistent Food Restriction in Patients with Anorexia Nervosa: A Scoping Review

The aetiology of anorexia nervosa (AN) presents a puzzle for researchers. Recent research has sought to understand the behavioural and neural mechanisms of these patients' persistent choice of calorie restriction. This scoping review aims to map the literature on the contribution of habit-based learning to food restriction in AN. PRISMA-ScR guidelines were adopted. The search strategy was applied to seven databases and to grey literature. A total of 35 studies were included in this review. The results indicate that the habit-based learning model has gained substantial attention in current research, employing neuroimaging methods, scales, and behavioural techniques. Food choices were strongly associated with dorsal striatum activity, and habitual food restriction based on the self-report restriction index was associated with clinical impairment in people chronically ill with restricting AN. High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and Regulating Emotions and Changing Habits (REaCH) have emerged as potential treatments. Future research should employ longitudinal studies to investigate the time required for habit-based learning and analyse how developmental status, such as adolescence, influences the role of habits in the progression and severity of diet-related illnesses. Ultimately, seeking effective strategies to modify persistent dietary restrictions controlled by habits remains essential.

Neural representations of anxiety in adolescents with anorexia nervosa: a multivariate approach

Anorexia nervosa (AN) is characterized by low body weight, fear of gaining weight, and distorted body image. Anxiety may play a role in the formation and course of the illness, especially related to situations involving food, eating, weight, and body image. To understand distributed patterns and consistency of neural responses related to anxiety, we enrolled 25 female adolescents with AN and 22 non-clinical female adolescents with mild anxiety who underwent two fMRI sessions in which they saw personalized anxiety-provoking word stimuli and neutral words. Consistency in brain response patterns across trials was determined using a multivariate representational similarity analysis (RSA) approach within anxiety circuits and in a whole-brain voxel-wise searchlight analysis. In the AN group there was higher representational similarity for anxiety-provoking compared with neutral stimuli predominantly in prefrontal regions including the frontal pole, medial prefrontal cortex, dorsolateral prefrontal cortex, and medial orbitofrontal cortex, although no significant group differences. Severity of anxiety correlated with consistency of brain responses within anxiety circuits and in cortical and subcortical regions including the frontal pole, middle frontal gyrus, orbitofrontal cortex, thalamus, lateral occipital cortex, middle temporal gyrus, and cerebellum. Higher consistency of activation in those with more severe anxiety symptoms suggests the possibility of a greater degree of conditioned brain responses evoked by personally-relevant emotional stimuli. Anxiety elicited by disorder-related stimuli may activate stereotyped, previously-learned neural responses within- and outside of classical anxiety circuits. Results have implications for understanding consistent and automatic responding to environmental stimuli that may play a role in maintenance of AN.

Hunger modulates perceptions of food health but not taste in restricted eaters

Introduction

Food taste and health perceptions are of particular interest for their implications on food choice. Most in vivo food choice studies experimentally control for hunger via a set preload or fast.

Methods

To explore how hunger may interact with these perceptions to impact food decisions, we compared taste and health perceptions of sweet and savory obesogenic food items among hungry or satiated participants with varying restrained eating tendencies.

Results

In our sample of 232 adults (M BMI = 25.9; M age = 36.4 yrs), highly palatable foods were perceived as tasty but unhealthy. Tastiness ratings were high, consistent across restrained eating groups, and unassociated with hunger. Perceptions of health, however, were impacted by the interaction of restrained eating group and hunger. Amongst hungry participants only, a graded association between restrained eating group and perceptions of health emerged for both food types. Specifically, hungry and highly restrained eaters viewed sweet foods as 2.8x healthier and savory foods as 2.1x healthier than their satiated counterparts.

Discussion

Our data suggest that hunger predicts differential health perceptions, but not tastiness ratings, among restrained eaters. We argue that the generalization of food perception data-especially among different eater types-may be limited if the continuum of hunger level is experimentally constrained. Therefore, hunger is a critical dynamic to consider in explorations of food perceptions and eating behavior in restrained eaters.