Neural correlates of body size estimation: A systematic review and narrative synthesis.

Inaccurate body size estimation (BSE), the discrepancy between an individual's actual and perceived body size and shape, is observed not only in clinical conditions like eating disorders and body dysmorphic disorder but also in healthy individuals. Understanding the neural mechanisms that support BSE is timely, given growing interest in perceptual biases and their potential relevance for identifying mechanisms that may be disrupted in clinical populations. However, the field has an incomplete understanding of brain systems functionally involved in BSE ability. To address this, we performed a systematic review, accompanied by a narrative synthesis, to identify brain regions associated with BSE across studies of healthy individuals. Studies using functional neuroimaging were selected if they elicited BSE with a task, contrasted BSE with a control task, and used whole-brain analyses (rather than being restricted to a priori regions of interest). This yielded a set of nine functional magnetic resonance imaging papers. There is relatively consistent involvement of ventral (fusiform/occipitotemporal regions) and dorsal (intraparietal areas) visual pathways, and discrete regions of the prefrontal cortex, suggesting recurring engagement of perceptual and higher-order cognitive systems during BSE. However, current knowledge is limited by the small number and heterogeneity of available studies. We identify both consistent and variable neural correlates of BSE, offering refined targets for future investigations of BSE in clinical populations. Based on these findings, we additionally provide specific suggestions for improving neuroimaging task design for future studies.