Anthropometric and Psychological Variables Associated with Body Mass Index: A Sex-Stratified Evaluation of Students from a Romanian University

Background: Evaluating non-invasive physical markers and psychological indicators offers useful insights into young adult body profiles. This cross-sectional study evaluated the potential associations and preliminary classification capacities of select anthropometric and psychological variables in relation to body mass index (BMI) status groupings. Methods: A cross-sectional evaluation was conducted on a cohort of 445 university students (nmale = 199, nfemale = 246) recruited from the University of Oradea. Anthropometric parameters (neck circumference, body adiposity index—BAI), a putative proxy prenatal biomarker (the right-hand R-2D:4D digit ratio), and psychosocial components (life satisfaction, total social support) were evaluated. Statistical models utilized multivariable linear regressions with collinearity diagnostics and exploratory Receiver Operating Characteristic (ROC) curve analysis. Results: Multivariable regressions accounted for a substantial proportion of BMI variance in males (Adjusted R2 = 0.853) and female participants (Adjusted R2 = 0.908). Neck circumference and BAI emerged as the primary statistically significant positive indicators. Standalone ROC curves suggested potential classification utility for the digital marker in both male (AUC = 0.745) and female participants (AUC = 0.805). Psychosocial metrics displayed no independent significant associations with somatic classifications. Conclusions: In this sample, young adult BMI categories are concurrently associated with physical parameters like neck circumference and BAI. The proposed cutting thresholds represent exploratory, internally derived thresholds specific to this convenience sample, which carry a potential mathematical optimism bias and require independent external validation before any clinical or institutional application can be evaluated.