Trends and inequalities in physical fitness and BMI among Chinese college students: an analysis of national surveys between 2019 and 2023

Background: Physical fitness and BMI among Chinese college students have undergone significant changes in recent years amid rapid socioeconomic transitions. Understanding these temporal patterns is essential for guiding effective health promotion strategies. Methods: Data were extracted from five cycles of the Exercise and physical health dataset of college students (2019-2023), including 58,892 college students aged 16-21. A standardized Physical Fitness Index (PFI) was constructed from six components: vital capacity (FVC), standing long jump (SLJ), sit-and -reach (SAR), muscle strength (MS), 50 m sprint (SR), and 800/1,000 m run (ER). Descriptive analyses evaluated annual, regional, and socioeconomic variations. Restricted cubic spline (RCS) regression models were conducted to assess the nonlinear relationship between BMI and PFI. Results: and a negative association outside this interval. Conclusion: From 2019 to 2023, Chinese college students showed declining fitness and rising obesity, with partial recovery. Marked regional inequalities persist, and a nonlinear BMI-PFI pattern indicates that maintaining a moderate BMI is optimal for overall fitness.