An exploration of the relationship between gastric interoceptive sensibility, body image, and food choice.

Body image (BI), how we perceive and feel about our body's appearance (Cash & Deagle, 1997), is informed by external bodily perceptions and interoceptive signals. Interoceptive sensibility, the subjective detection and appraisal of internal bodily sensations originating from our visceral organs (heart, lungs, stomach; Garfinkel et al., 2015), is important for disorders of disturbed BI, like eating disorders (EDs). A diagnostic hallmark of EDs is a disturbed body image (American Psychological Association, 2013), as anorexia nervosa (AN) patients in particular overestimate their body size and negatively evaluate their body (Hagman et al. 2015).
ED patients show interoceptive sensibility differences compared to healthy participants (Jenkinson et al. 2018) on The Eating Disorder Inventory (EDI; Garner, Olmsted, & Polivy, 1983) and Multidimensional Assessment of Interoceptive Awareness (MAIA; Mehling et al., 2012). However, the EDI and MAIA measure interoceptive sensibility across the whole body, masking the contribution of specific body systems to BI.
Gastric interoceptive sensibility (GIS) is particularly relevant to BI as those with subclinical and clinical EDs are found to have disturbed gastric interoception (van Dyck et al., 2020). GIS, measured by the Water Loading-II questionnaire, also correlates with BI (Todd et al., 2020). However, this questionnaire does not comprehensively capture GIS. This is because it was developed using data from a small sample, is unidimensional, and focuses on the negative evaluation of gastric sensations (e.g. asking about discomfort and guilt), making it relevant to fullness rather than satiation, two distinct sensations (van Dyck et al., 2016). Furthermore, this scale has not been empirically validated. Therefore, we aim to develop a GIS scale using thematic, explanatory factor, confirmatory factor, and hierarchical multiple regression analyses.
To extend previous research showing a correlation between GIS and BI (Todd et al., 2020), the new scale will be used to investigate if GIS and BI directly modulate each other. GIS and BI will be manipulated by water-loading and avatar body size in a virtual reality full-body illusion, respectively. Evidencing a modulatory link between GIS and BI would make the new scale useful for identifying individuals at an ED risk, a major advantage considering the high mortality rate and poor health outcomes of these patients (Field et al., 2012; Mascolo, Trent, Colwell, & Mehler, 2012; Smink, Van Hoeken & Hoek, 2012). Furthermore, understanding the unique role of gastric interoception will contribute to the wider theory of the multidimensional nature of interoceptive sensibility and its impact on mental health.
Although there is evidence for a relationship between interoception and body image, there is limited research exploring the role of both in food choice. Hunger and satiety, sensations arising from the gastric system, have been linked to food choice (Benelam, 2009; Tuorila et al., 2001). The role of body image in food choices is less clear. Verhulst et al., (2018) used virtual reality to manipulate perceived body size, but found this to have no influence on food choices. Conversely, Tambone et al. (2021) found that embodying a slim avatar induced avoidance of high calorie food. These mixed findings may be because neither study controlled for gastric interoception. Therefore, we aim to computationally model the relative contributions of GIS and BI to food choices. Drift diffusion modelling shows how GIS and BI influence food choice. Understanding this is crucial for developing tools to encourage healthy food choices. This may be an important step, not just for psychiatric conditions such as AN, but also for tackling obesity, a growing health concern in the western world (World Health Organisation, 2021).