Body-scaled action in obesity during locomotion: Insights on the nature and extent of body representation disturbances

The perception of affective touch in women affected by obesity

Introduction

Pleasant and comforting bodily contacts characterized intimate and affective interactions. Affective touch informs us about others' emotions and intentions, sustains intimacy and closeness, protecting from loneliness and psychological distress. Previous evidence points to an altered experience of affective touch in clinical populations reporting interpersonal difficulties. However, there is no investigation of affective touch in obesity, which is often associated with negative affective-relational experiences since childhood.

Methods

This study aimed to provide the first evidence about the experience of affective touch in obesity by comparing 14 women with obesity with 14 women with healthy weight. Participants rated the pleasantness of both imagined and actual tactile stimuli, which consisted of (i) soft-brush strokes, (ii) touches of the experimenter's hand, and (iii) of a plastic stick (as control, non-affective, stimulation). Participants should report the pleasantness of each kind of touch. Moreover, we explored lifespan experiences of affective touch and interpersonal pleasure in social contexts through self-report questionnaires.

Results

No differences emerged for the pleasantness of affective touch (in both the real and imagery task) between the two groups. However, participants with obesity reported less frequent and less satisfying early experiences of affective touch when compared with the controls.

Discussion

Our results spoke in favor of a preserved experience of affective touch when experimentally probed in obesity, despite a limited early exposure to bodily affective contacts. We interpreted our results in the light of the social reconnection hypothesis. Nevertheless, we provided crucial methodological considerations for future research, considering that both the experimenter's and the brush touch may not resemble adequately real-life experiences, in which affective touch involves intimate people.

Influencing the body schema through the feeling of satiety

The body schema is a much discussed aspect of body awareness. Although there is still no single definition, there is widespread consensus that the body schema is responsible for movement and interaction with the environment. It usually remains outside of active consciousness. There are only few investigations on influences on the body schema and none of them investigated feeling of satiety or hunger. Thirty-two healthy women were investigated twice, one time sat and the other time hungry. To measure the body schema, we used a door-like-aperture and compared the critical aperture-to-shoulder-ratio (cA/S). A cover story was used to ensure that the unconscious body schema has been measured. We found a significantly higher cA/S for satiety compared to hungry, which indicates that during satiety participants rotate their shoulders for relatively larger door compared to hunger, unconsciously estimating their body size to be larger. We showed that even a moderate rated feeling of hunger or satiety leads to an adjustment in body-scaled action and consequently also an adaptation of body schema. It suggests that, in addition to the visual-spatial and the proprioceptive representation, somatic information can also be relevant for the body schema.

EXPRESS: Does physical weight alter the mental representation of the body? Evidence from motor imagery in obesity

OBJECTIVE

Obesity is a clinical condition that impacts severely the physical body. However, evidence related to the mental representation of the body in action is scarce. The few available studies only focus on avoiding obstacles, rather than participants imagining their own body.

METHOD

To advance knowledge in this field, we assessed the performance of twenty-two individuals with obesity compared to thirty individuals with a healthy weight in two tasks that implied different motor (more implicit vs. more explicit) imagery strategies. Two tasks were also administered to control for visual imagery skills, to rule out confounding factors. Moreover, we measured body uneasiness, through a standard questionnaire, as body image negativity could impact on other body representation components.

RESULTS

Our findings do not show differences in the motor imagery tasks between individuals with obesity and individuals with healthy weight. On the other hand, some differences emerge in visual imagery skills. Crucially, individuals with obesity did report a higher level of body uneasiness.

CONCLUSIONS

Despite a negative body image and visual imagery differences, obesity per se does not impact on the representation of the body in action. Importantly, this result is independent from the level of awareness required to access the mental representation of the body.

Body size estimation in obesity: a systematic review and meta-analysis

Previous research about body size estimation in obesity reported heterogeneous results. This might be related to the fact that the tasks adopted explored different body representations. Classifying the previous studies according to the specific body representation probed (i.e. implicit, explicit or both) might clarify discordant findings. A systematic review and meta-analysis of research articles assessing body size estimation in individuals affected by obesity compared with healthy weight individuals were performed in PubMed and Web of Science. Additional records were identified by reference lists inspection. The last search was run in May 2021. Two independent authors performed data extraction according to predefined criteria. Both groups either overestimated or underestimated the implicit body representation depending on the task used and the body part considered. Conversely, the explicit representation of the body was mainly overestimated by both individuals with obesity and healthy weight. In tasks relying on both these representations, overestimation and underestimation were reported in both groups, possibly depending on the degree of which each procedure relied on the explicit and/or implicit representation of the body. According to the meta-analysis, individuals with obesity tended to be significantly less accurate in body size estimations than participants with healthy weight. We confirmed that heterogeneous findings in body size estimation in obesity are related to the adoption of different tasks, which likely involve different body representations. We discussed the role of body dissatisfaction and altered somatosensation in the lower accuracy observed in obesity.

Social Support for People with Morbid Obesity in a Bariatric Surgery Programme: A Qualitative Descriptive Study

Background—Morbid obesity (MO) is a chronic metabolic disease affecting physical, psychological and social wellbeing. Bariatric surgery is a reliable method for losing weight in the long term, improving the quality of life, body image and social life of people with MO. Current literature recognises the importance of social support in controlling weight and coping with MO. The objective of this study was to describe and understand experiences related to social support for patients with MO included in a bariatric surgery programme. Methods—A qualitative descriptive study, where data collection included thirty-one interviews with people diagnosed with MO involved in a bariatric surgery programme. Results—Three main themes emerged from the analysis: (1) accepting the problem in order to ask for help, (2) the need for close support and (3) professional support: opposing feelings. Conclusions—A partner, family and friends are the key pillars of social support for those with MO included in a bariatric surgery programme. Healthcare professionals gave formal support; the bariatric surgery team provided information, trust and assurance. Nurses provided healthcare 24 h a day, making them the main formal support for people in the bariatric surgery programme.

An Investigation of Lower Limb Representations Underlying Vision, Touch, and Proprioception in Body Integrity Identity Disorder

Individuals with Body Integrity Identity Disorder (BIID) have a (non-psychotic) longstanding desire to amputate or paralyze one or more fully-functioning limbs, often the legs. This desire presumably arises from experiencing a mismatch between one's perceived mental image of the body and the physical structural and/or functional boundaries of the body itself. While neuroimaging studies suggest a disturbed body representation network in individuals with BIID, few behavioral studies have looked at the manifestation of this disrupted lower limb representations in this population. Specifically, people with BIID feel like they are overcomplete in their current body. Perhaps sensory input, processed normally on and about the limb, cannot communicate with a higher-order model of the leg in the brain (which might be underdeveloped). We asked individuals who desire paralysis or amputation of the lower legs (and a group of age- and sex-matched controls) to make explicit and implicit judgments about the size and shape of their legs while relying on vision, touch, and proprioception. We hypothesized that BIID participants would mis-estimate the size of their affected leg(s) more than the same leg of controls. Using a multiple single-case analysis, we found no global differences in lower limb representations between BIID participants and controls. Thus, while people with BIID feel that part of the body is foreign, they can still make normal sensory-guided implicit and explicit judgments about the limb. Moreover, these results suggest that BIID is not a body image disorder, per se, and that an examination of leg representation does not uncover the disturbed bodily experience that individuals with BIID have.

The Effect of a Virtual-Reality Full-Body Illusion on Body Representation in Obesity

Background. The effective illusory ownership over an artificial body in modulating body representations in healthy and eating disorders population has been repeatedly reported in recent literature. In this study, we extended this research in the field of obesity: specifically, we investigated whether ownership over a virtual body with a skinny abdomen might be successfully experienced by participants affected by obesity. Methods. Fifteen participants with obesity and fifteen healthy-weight participants took part at this study in which the VR-Full-Body Illusion was adopted. The strength of illusion was investigated through the traditional Embodiment Questionnaire, while changes in bodily experience were measured through a body size estimation task. Results. Participants with obesity as well as healthy-weight participants reported to experience the illusion. About the body size estimation task, both groups reported changes only in the estimation of the abdomen’s circumference after the experimental condition, in absence of any another difference. Discussion. Participants with obesity reported to experience the illusion over a skinny avatar, but the modulation of the bodily experience seems controversial. Future lines of research exploiting this technique for modulating body representations in obesity, specifically in terms of potential therapeutic use, were discussed.

Negative Body Image Is Not Related to Spontaneous Body-Scaled Motoric Behavior in Undergraduate Women

Body image disturbance is a core characteristic of anorexia nervosa, which might be grounded in distortions in schematic body representations. In line with this, several studies showed that when walking through door-like apertures of different widths, individuals with anorexia nervosa move as if their bodies are larger than they actually are. They turn their body at a higher aperture/shoulder width ratio than healthy individuals. We examined whether oversized body-scaled motoric behaviors may not be restricted to anorexia nervosa but concern a general feature of negative body image attitudes. Therefore, we investigated the relation between negative body image as assessed with shape and weight concerns subscales of the Eating Disorder Examination Questionnaire and aperture/shoulder width turning ratios in women with a healthy weight (n = 62). We found that a more negative body image was unrelated to higher aperture/shoulder width turning ratios. Bayes analysis provided moderate evidence for the null hypothesis that spontaneous body-scaled motoric behaviors are not involved in negative body image. Future studies should disentangle whether being underweight per se is related to distinctive spontaneous body-scaled motoric behaviors or whether an "oversized" body schema is a unique characteristic of anorexia nervosa, potentially contributing to the persistence of this disorder.