Associations of Overall Diet Quality and Individual Dietary Behaviours with Anthropometric Outcomes Among Chilean University Students

Background/Objectives: Diet quality is an important determinant of health during young adulthood; however, associations between dietary behaviours and anthropometric outcomes in university students remain insufficiently understood. This study examined the associations between dietary behaviours and anthropometric indicators in Chilean university students. Methods: A cross-sectional study was conducted among university students from southern Chile between June and November 2025. Dietary habits were assessed using a validated Chilean dietary habits questionnaire, from which Healthy Eating, Unhealthy Eating, and Overall Diet scores were derived. Anthropometric measurements included body mass index (BMI), waist circumference, and waist-to-height ratio (WHtR). Age- and sex-adjusted multivariable linear regression models were fitted. Exploratory analyses included psychometric evaluation, principal component analysis, false discovery rate (FDR) correction, and dietary behaviour network analysis. Results: A total of 374 students were included, of whom 40.3% were women. Psychometric analyses provided only partial support for the predefined two-domain structure, with stronger properties for the healthy domain. None of the predefined dietary scores were associated with BMI. The Unhealthy Eating Score was nominally positively associated with waist circumference (β = 0.285 cm per score point, 95% CI: 0.011–0.560), although this association did not remain statistically significant after FDR correction. Exploratory item-level analyses identified positive associations between sugar-sweetened beverage consumption and waist circumference and inverse associations between breakfast consumption and BMI after FDR correction. Conclusions: Predefined dietary behaviour scores showed limited associations with anthropometric outcomes. Psychometric analyses provided only partial support for the predefined scoring structure, particularly for the unhealthy dietary domain. Exploratory item-level analyses suggested that specific dietary behaviours may provide complementary information beyond that obtained by composite dietary scores, although these findings require confirmation in prospective longitudinal studies and further psychometric validation.