Neural Responses to Fat Talk Depend on Body Weight: An fNIRS Study in Natural Conversations

Fat talk—self-critical comments about weight or body—is common, especially among young women. It leads to body image issues like body surveillance and dissatisfaction, but individuals might recover by disengaging from fat talk. This study aims to investigate the neural mechanisms underlying fat talk, with particular emphasis on the moderating role of body weight. A total of 116 participants took part in a fat talk session, which was preceded and followed by discussions on non-body-related topics, such as sharing travel experiences or discussing room decor. These discussions were referred to as the pre-test and post-test talks, respectively. Brain activity in the frontal and parietal regions was continuously recorded using fNIRS throughout all phases. Results showed that participants with higher Body Mass Index (BMI) reported increased body surveillance following the fat talk, which subsided after the post-test talk; this pattern was not observed in participants with lower BMI. Neuroimaging findings revealed that higher BMI was associated with decreased functional connectivity among brain regions involved in body-related cognitive control during the fat talk, and increased connectivity in regions associated with emotional regulation during the post-test talk. In contrast, participants with lower BMI exhibited enhanced connectivity in cognitive control regions related to body surveillance both during and after the fat talk. These findings suggest distinct neural and regulatory responses to fat talk based on body weight.