Examining the association between body trust and body mass index with quantile regression

Schachter's externality theory posits a connection between the inability to eat according to internal cues and higher body mass index (BMI); however, related work has not investigated associations between body trust and the wide range of BMIs found in general samples. This study examined the association between body trust and BMI across levels of BMI to determine whether this relationship differed as a function of BMI level.

Participants were 534 adults (55.4% female), mean age 36 years, BMIs 15.13-67.90 (M = 27.89, SD = 7.25), recruited via MTurk. They completed self-report assessments of body trust, height, and weight. Quantile regression was utilized to estimate effects of body trust on BMI at five equidistant quantiles of BMI.

Overall linear regression analyses indicated that body trust was significantly negatively associated with BMI. Quantile regression revealed a significant negative relationship at each quantile of BMI, and Wald tests indicated the association was significantly stronger at the 0.7 and 0.9 quantiles than at the 0.1, 0.3, and 0.5 quantiles, which did not differ.

Quantile regression identified a stronger relationship between body trust and BMI at 0.7 and 0.9 quantiles than at 0.1, 0.3, and 0.5 quantiles of BMI. Results align with the externality hypothesis, which suggests those at higher weights experience difficulty using internal cues to guide eating. A weaker-than-expected association between body trust and low BMI may be due to restricted range (few low-BMI participants). Replication in eating disorder samples is merited.

Level V, cross-sectional descriptive study.