Evidence for a perceptual mechanism relating body size misperception and eating disorder symptoms

Perceptual Dysfunction in Eating Disorders

Eating disorders (EDs) are characterized by abnormal responses to food and weight-related stimuli and are associated with significant distress, impairment, and poor outcomes. Because many of the cardinal symptoms of EDs involve disturbances in perception of one's body or abnormal affective or cognitive reactions to food intake and how that affects one's size, there has been longstanding interest in characterizing alterations in sensory perception among differing ED diagnostic groups. Within the current review, we aimed to critically assess the existing research on exteroceptive and interoceptive perception and how sensory perception may influence ED behavior. Overall, existing research is most consistent regarding alterations in taste, visual, tactile, and gastric-specific interoceptive processing in EDs, with emerging work indicating elevated respiratory and cardiovascular sensitivity. However, this work is far from conclusive, with most studies unable to speak to the precise etiology of observed perceptual differences in these domains and disentangle these effects from affective and cognitive processes observed within EDs. Further, existing knowledge regarding perceptual disturbances in EDs is limited by heterogeneity in methodology, lack of multimodal assessment protocols, and inconsistent attention to different ED diagnoses. We propose several new avenues for improving neurobiology-informed research on sensory processing to generate actionable knowledge that can inform the development of innovative interventions for these serious disorders.

Sizing up the crowd: Assessing spatial integration difficulties in body size judgements across eating disorder symptomatology

Introduction

Body size judgements are frequently biased, or inaccurate, and these errors are further exaggerated for individuals with eating disorders. Within the eating disorder literature, it has been suggested that exaggerated errors in body size judgements are due to difficulties with integration. Across two experiments, we developed a novel integration task, named the Ebbinghaus Illusion for Bodies in Virtual Reality (VR), to assess whether nearby bodies influence the perceived size of a single body. VR was used to simulate the appearance of a small crowd around a central target body.

Method and Results

In Experiment 1 (N = 412), participants were required to judge the size of a central female target within a crowd. Experiment 1 revealed an Ebbinghaus Illusion, in which a central female appeared larger when surrounded by small distractors, but comparatively smaller when surrounded by large distractors. In other words, the findings of Experiment 1 demonstrate that surrounding crowd information is integrated when judging an individual's body size; a novel measure of spatial integration (i.e., an Ebbinghaus Illusion for Bodies in VR). In Experiment 2 (N = 96), female participants were selected based on high (n = 43) and low (n = 53) eating disorder symptomatology. We examined whether the magnitude of this illusion would differ amongst those with elevated versus low eating disorder symptomatology, in accordance with weak central coherence theory, with the high symptomatology group displaying less spatial integration relative to the low group. The results of Experiment 2 similarly found an Ebbinghaus Illusion for Bodies in VR. However, illusion magnitude did not vary across high and low symptomatology groups.

Discussion

Overall, these findings demonstrate that surrounding crowd information is integrated when judging individual body size; however, those with elevated eating disorder symptomatology did not show any integration deficit on this broader measure of spatial integration.

The impact of weight loss diet programs on anemia, nutrient deficiencies, and organ dysfunction markers among university female students: A cross-sectional study

Practicing restricted weight loss diet programs (WLDPs) without proper supervision can result in nutritional deficiency, which can lead to the development of several nutritional disorders. The current cross-sectional study aimed to investigate the impact of WLDPs practiced by university female students on the prevalence of micronutrient deficiencies, anemia, and organs dysfunction, and to assess the association of identified anomalies with dieting practices and dietary habits of university female students. A total of 185 (105 dieting and 80 non-dieting) volunteers’ female students at Al-Hussein Bin Talal University participated in this study. After the participants answered a questionnaire, blood samples were collected for hematological and biochemical analysis, and the body mass index (BMI) was determined. The results show that there were no significant differences between dieting and non-dieting groups in biochemical markers of kidney and liver functions as well as serum levels of copper, zinc, and folate. On the other hand, dieting participants exhibited significantly lower level of hemoglobin, serum ferritin, iron, and vitamin B12 than encounter group (p<0.05). Attempting WLDPs significantly increased the prevalence of anemia (46.7%), iron deficiency (57.1%), and iron deficiency anemia (IDA) (41.9%), comparing to non-dieting students (28.7%, 33.8%, and 15.0%, respectively) (p<0.005). Chi-square test showed that the development of anemia among dieting girls was significantly dependence of several factors including BMI category, source and duration of the diet programs, and skipping breakfast (p<0.05). In conclusion, young girls attempting WLDPs without professional guidance are more prone to the risk of nutrients deficiencies and the development nutritional disorders like IDA. An educational program should be employed to teach young females on when and how to adopt healthy WLDPs.

Body Image Software Programs

The assessment of body image has evolved in recent decades through the development of various software programs. However, it is not yet known whether this technological advance has resulted in refined evidence or whether this assessment development has been extensively applied in the field. This study reviewed the body image software programs developed and applied from 2000 to 2020. Searches were systematically conducted in four scientific databases. A total of 35 articles were selected, and 13 body image software programs were identified. The main features comprising the variability of the software were the pattern of body stimuli presentation (avatars x real body x body drawings) and the procedures of body image manipulation (whole body adjustment x adjustment of separate body parts). Heterogeneity was prevalent among the studies reviewed and prevented a favorable conclusion regarding the use of software compared to other body image assessment strategies.

EXPRESS: The Influence of Three-Dimensional Cues on Body Size Judgements

Research has shown that body size judgements are frequently biased, or inaccurate. Critically, judgement biases are further exaggerated for individuals with eating disorders, a finding that has been attributed to difficulties integrating body features into a perceptual whole. However, current understanding of which body features are integrated when judging body size is lacking. In this study, we examine whether individuals integrate three-dimensional (3D) cues to body volume when making body size judgements. Computer-generated body stimuli were presented in a 3D Virtual Reality (VR) environment. Participants (N = 412) were randomly assigned to one of two conditions: in one condition the to-be-judged body was displayed binocularly (containing 3D cues to body volume), in the other, bodies were presented monocularly (2D cues only). Across 150 trials, participants were required to make a body size judgement of a target female body from a third-person point of view using an unmarked visual analogue scale (VAS). It was found that 3D cues significantly influenced body size judgements. Namely, thin 3D bodies were judged smaller, and overweight 3D bodies were judged larger, than their 2D counterpart. Furthermore, to reconcile these effects, we present evidence that the two perceptual biases, regression to the mean and serial dependence, were reduced by the additional 3D feature information. Our findings increase our understanding of how body size is perceptually encoded and creates testable predictions for clinical populations exhibiting integration difficulties.

Food Allergy, Eating Disorders and Body Image

Background/Introduction:

Food allergy (FA) management involves avoiding allergenic foods to prevent an adverse reaction. Affected individuals spend substantial amounts of time thinking about food and the impact it has on their bodies. As such, we posit sustained awareness of food choices may contribute to distorted body image and disordered eating. We performed a narrative review to glean insight into associations between FA, body image and eating disorders.

Methods:

A literature search of Scopus, PsycINFO, PubMed and Google Scholar was conducted connecting terms for “food allergy” with terms for “body image” and “eating disorders”. Title and abstract screening were independently performed by two reviewers, with relevant abstracts carried forward to full text screening.

Results:

159 articles were eligible for full text screening and a total of 12 publications were ultimately included in this narrative review, and 1 article from the grey literature. Adolescents and adults both reported feeling as though their bodies were “defective” and were found to have integrated their FA as a stable facet of their identities. In addition, FA was overwhelmingly associated with prevalence of eating disorders and eating disorder-like symptoms. Disturbed body image was found to be a mediating variable for the development of disordered patterns of eating in food allergic individuals.

Limitations:

Few studies appeared to consider comorbidities as confounders. Also, many studies employed convenience sampling, which does limit generalizability of conclusions.

Discussion/Conclusion:

Based on a small body of literature, there appears to be a potential association between FA and distorted body image and disordered eating.

The relationship between body weight and dietary restraint is explained by body dissatisfaction and body image inflexibility among young adults in China

OBJECTIVE

Eating disorders and obesity are commonly recognized as key public health concerns worldwide. Although rates of obesity and disordered eating have traditionally been lower in China than Western countries, these rates are on the rise. As such, interest is growing in identifying mechanisms that may address these conditions. While associations between body weight and dissatisfaction are well established, burgeoning research aims to examine how these factors are related to dietary restraint and body image inflexibility. This study aimed to explore the possible mediation effect of body dissatisfaction and body image inflexibility between body weight (body mass index) and dietary restraint. Furthermore, we explored how these relationships differed across men and women.

METHODS

A sample of 1068 young adults (563 females and 505 males) in China participated in the study. Participants completed the Eating Disorder Inventory and Three-Factor Eating Questionnaire as well as the Body Image-Acceptance and Action Questionnaire.

RESULTS

Results showed that: (1) body dissatisfaction and body image inflexibility fully mediated the relationship between body mass index and dietary restraint; (2) this model fit both genders, although differences were found in the regression coefficients between the mediation model for men and women.

CONCLUSION

These findings support body image dissatisfaction and inflexibility as mediators of the relationship between body weight and dietary restraint, highlighting these as potential mechanisms for treatment.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

Visual perception and dissociation during Mirror Gazing Test in patients with anorexia nervosa: a preliminary study

PURPOSE

It has been widely shown that dissociative features might play a fundamental role in producing body image distortions in patients affected by eating disorders. Here, we hypothesize that the Mirror Gazing Test (MGT), a task consisting in mirror exposure in a condition of sensory deprivation, would elicit dissociative symptoms in a group of patients with anorexia nervosa (AN).

METHODS

Fourteen patients with AN and fourteen healthy controls (HC) underwent a 10 min MGT and completed the Strange Face Questionnaire and a short version of the Clinician-Administered Dissociative States Scale, along with a psychological assessment for eating disorders psychopathology, anxiety and depression.

RESULTS

AN patients reported a higher number of strange-face apparitions and dissociative sensations than HC during the MGT. Dissociative identity (compartmentalization of two or more identities) and depersonalization (detachment of bodily-self) were much higher in patients with AN than in HC. These findings were correlated with body dissatisfaction and disruption in interoceptive awareness.

CONCLUSION

Dissociation and body image dysfunction are strongly connected in the pathophysiology of anorexia nervosa. Future research should investigate the same aspects in other psychiatric conditions characterized by body image distortions, such as Body Dysmorphic Disorder.

LEVEL OF EVIDENCE

I, Experimental studies.

Perceptual Oscillations in Gender Classification of Faces, Contingent on Stimulus History

Perception is a proactive ‘‘predictive’’ process, in which the brain takes advantage of past experience to make informed guesses about the world to test against sensory data. Here we demonstrate that in the judgment of the gender of faces, beta rhythms play an important role in communicating perceptual experience. Observers classified in forced choice as male or female, a sequence of face stimuli, which were physically constructed to be male or female or androgynous (equal morph). Classification of the androgynous stimuli oscillated rhythmically between male and female, following a complex waveform comprising 13.5 and 17 Hz. Parsing the trials based on the preceding stimulus showed that responses to androgynous stimuli preceded by male stimuli oscillated reliably at 17 Hz, whereas those preceded by female stimuli oscillated at 13.5 Hz. These results suggest that perceptual priors for face perception from recent perceptual memory are communicated through frequency-coded beta rhythms.

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Perception is strongly influenced by prior expectations and perceptual experience

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We show perceptual priors for face perception are communicated through beta rhythms

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Priors for male and female are communicated via distinct beta frequencies

Executive functioning and spatial processing in anorexia nervosa: an experimental study and its significance for the allocentric lock theory

PURPOSE

The allocentric lock theory (ALT) suggests that people with eating disorders have difficulties in multisensory integration in two reference frames-egocentric and allocentric, whereby the egocentric, but not allocentric, is impaired. This leads to a distorted body image that contributes to the development and maintenance of the disorder. The current study aimed to explore a facet of the ALT, namely, the visuo-spatial aspect, and its relation to cognitive flexibility in patients with anorexia nervosa (AN).

METHODS

Fifty-five participants took part in the study: 20 AN patients and 35 controls, matched by age and education. The object perspective taking test (OPTT) and the mental rotation test (MRT), tapping egocentric and allocentric representations, respectively, and a set-shifting task were administered. The brief symptom inventory was used to measure overall levels of distress.

RESULTS

AN patients showed higher level of distress. They performed poorer on the OPTT and set-shifting task but not on the MRT. The OPTT and MRT were correlated for controls but not for AN patients, while the set-shifting task and body mass index were associated with the OPTT but not with the MRT for the AN patients.

CONCLUSIONS

The findings support the ALT by demonstrating impaired visual egocentric representations and intact allocentric visual functions in AN patients, with cognitive flexibility associated only with the egocentric frame. Therefore, egocentric frame impairment in AN patients may be influenced by visual perception and cognitive flexibility deficiency.

LEVEL OF EVIDENCE

Level III: case-control analytic study.

Increased anticipatory brain response to pleasant touch in women remitted from bulimia nervosa

Bulimia nervosa (BN) is characterized by affective instability and dysregulated behaviors (binge eating, fasting, self-induced vomiting) that disrupt bodily homeostasis. Mechanisms underlying dysregulation in BN are unclear, although altered reward responsivity, anticipatory processing of environmental cues, and interoception (detection and integration of body-state signals to regulate behavior) have been implicated in BN pathophysiology. We aimed to determine whether BN is associated with ineffectively predicting body state or integrating predicted experience with actual experience by examining neural response to anticipation and experience of affective touch, a pleasant interoceptive stimulus that acts on sensory and emotional systems to guide behavior. During fMRI, we administered soft strokes to the palm and forearm in women remitted from BN (RBN; N = 23) and control women (CW; N = 25). A Group (RBN/CW) × Condition (anticipation/touch) interaction was found in the right dorsal caudate; both CW and RBN had increased activation during touch compared with anticipation, with RBN demonstrating marginally greater anticipatory response than CW. For RBN, those individuals who showed greater anticipatory response in the dorsal caudate also reported higher levels of harm avoidance. RBN individuals relative to CW showed greater activation in left putamen and insula during the anticipation but not when experiencing an affective touch. This increase during anticipation rather than the actual experience of the affective touch is consistent with a top-down preparatory process which is associated with harm avoidance and is similar to what has been observed in anxious individuals. This aberrant signal integration could disrupt feedback processing, serving to maintain disordered behavior.

Individual Differences in Serial Dependence of Facial Identity are Associated with Face Recognition Abilities

Serial dependence is a perceptual bias where current perception is biased towards prior visual input. This bias occurs when perceiving visual attributes, such as facial identity, and has been argued to play an important functional role in vision, stabilising the perception of objects through integration. In face identity recognition, this bias could assist in building stable representations of facial identity. If so, then individual variation in serial dependence could contribute to face recognition ability. To investigate this possibility, we measured both the strength of serial dependence and the range over which individuals showed this bias (the tuning) in 219 adults, using a new measure of serial dependence of facial identity. We found that better face recognition was associated with stronger serial dependence and narrower tuning, that is, showing serial dependence primarily when sequential faces were highly similar. Serial dependence tuning was further found to be a significant predictor of face recognition abilities independently of both object recognition and face identity aftereffects. These findings suggest that the extent to which serial dependence is used selectively for similar faces is important to face recognition. Our results are consistent with the view that serial dependence plays a functional role in face recognition.

Looking at the Figures: Visual Adaptation as a Mechanism for Body-Size and -Shape Misperception

Many individuals experience body-size and -shape misperception (BSSM). Body-size overestimation is associated with body dissatisfaction, anxiety, depression, and the development of eating disorders in individuals who desire to be thinner. Similar symptoms have been noted for those who underestimate their muscularity. Conversely, individuals with high body mass indices (BMI) who underestimate their adiposity may not recognize the risks of or seek help for obesity-related medical issues. Although social scientists have examined whether media representations of idealized bodies contribute to the overestimation of fat or underestimation of muscle, other scientists suggest that increases in the prevalence of obesity could explain body-fat underestimation as a form of renormalization. However, these disparate approaches have not advanced our understanding of the perceptual underpinnings of BSSM. Recently, a new unifying account of BSSM has emerged that is based on the long-established phenomenon of visual adaptation, employing psychophysical measurements of perceived size and shape following exposure to "extreme" body stimuli. By inducing BSSM in the laboratory as an aftereffect, this technique is rapidly advancing our understanding of the underlying mental representation of human bodies. This nascent approach provides insight into real-world BSSM and may inform the development of therapeutic and public-health interventions designed to address such perceptual errors.

An Assessment of Computer-Generated Stimuli for Use in Studies of Body Size Estimation and Bias

Inaccurate body size judgments are associated with body image disturbances, a clinical feature of many eating disorders. Accordingly, body-related stimuli have become increasingly important in the study of estimation inaccuracies and body image disturbances. Technological advancements in the last decade have led to an increased use of computer-generated (CG) body stimuli in body image research. However, recent face perception research has suggested that CG face stimuli are not recognized as readily and may not fully tap facial processing mechanisms. The current study assessed the effectiveness of using CG stimuli in an established body size estimation task (the “bodyline” task). Specifically, we examined whether employing CG body stimuli alters body size judgments and associated estimation biases. One hundred and six 17- to 25-year-old females completed the CG bodyline task, which involved estimating the size of full-length CG body stimuli along a visual analogue scale. Our results show that perception of body size for CG stimuli was non-linear. Participants struggled to discriminate between extreme bodies sizes and overestimated the size change between near to average bodies. Furthermore, one of our measured size estimation biases was larger for CG stimuli. Our collective findings suggest using caution when employing CG stimuli in experimental research on body perception.

Visuo-tactile congruency influences the body schema during full body ownership illusion

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Visuo-tactile congruency influences the body schema, but not the body image.

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Movement behavior may provide a window into the unconscious body schema.

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We present novel methods to distort avatars and Euclidean space in virtual reality.

Previous research showed that full body ownership illusions in virtual reality (VR) can be robustly induced by providing congruent visual stimulation, and that congruent tactile experiences provide a dispensable extension to an already established phenomenon. Here we show that visuo-tactile congruency indeed does not add to already high measures for body ownership on explicit measures, but does modulate movement behavior when walking in the laboratory. Specifically, participants who took ownership over a more corpulent virtual body with intact visuo-tactile congruency increased safety distances towards the laboratory’s walls compared to participants who experienced the same illusion with deteriorated visuo-tactile congruency. This effect is in line with the body schema more readily adapting to a more corpulent body after receiving congruent tactile information. We conclude that the action-oriented, unconscious body schema relies more heavily on tactile information compared to more explicit aspects of body ownership.