Risk Identification and Improvement Strategies for BMI and Physical Fitness and Health Grade Cross-Classification: A Cross-Sectional Study Based on Chinese College Students

Hao Guo^*

• Zhumadian Preschool Education College, Zhumadian, China

Physical fitness decline among university students has become a global concern. Single-metric evaluation methods cannot comprehensively reflect students' health status. This study aims to establish a BMI-Physical Fitness and Health (PFAH) cross-classification framework to identify distinct risk groups and their characteristics, providing evidence for targeted intervention strategies. This cross-sectional study examined 3,026 Chinese college students (1,435 males, 1,591 females, aged 18-22 years) using the National Student Physical Fitness and Health Standard. Students were cross-classified based on BMI categories (normal, overweight, obese) and PFAH levels (good, pass, fail), forming eight distinct groups. Heat maps, radar charts, and ROC curve analyses were used to characterize group features and identify predictive indicators. The study found that: (1) Normal-pass group was most prevalent (52.1%), followed by normal-good (22.2%) and overweight-pass (11.6%); (2) High-risk groups (obesity-pass, normal-fail, overweight-fail, and obesity-fail) constituted 3.0%, 4.7%, 2.5%, and 3.0% of the sample, respectively; (3) High-risk groups exhibited distinct fitness deficiencies: obesity-pass group showed significantly elevated BMI (z=2.45); normal-fail group demonstrated poor speed performance (50m: z=0.69); overweight-fail group showed deficiencies in flexibility (sit-and-reach: z=-0.47) and muscular endurance (sit-ups: z=-0.45); obesity-fail group performed worst in cardiopulmonary endurance (1000m: z=1.60; 800m: z=2.30) and muscular strength (pull-ups: z=-0.86); (4) BMI, endurance capacity (1000m/800m), and speed (50m) were the strongest predictors for identifying high-risk males (AUC: 0.902, 0.801, 0.792) and females (AUC: 0.895, 0.874, 0.731). The BMI-PFAH cross-classification framework effectively identifies diverse risk profiles among university students, especially revealing "hidden risk populations" (normal BMI but failing fitness) that traditional single-metric approaches might overlook. Based on this framework, university physical education should implement personalized interventions addressing specific needs: weight management while maintaining fitness for the obesity-pass group; anaerobic capacity and speed training for the normal-fail group; and comprehensive improvement in cardiopulmonary function, muscular strength, and flexibility for overweight/obesity-fail groups. This study provides empirical evidence for developing targeted health education policies and interventions in higher education settings.