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 Between 2019 and 2023, the prevalence of thinness decreased from 13% to 8.3%, while overweight and obesity increased from 21.5% to 28.6%. The overall median PFI declined from −0.1 (−2.2, 2.2) in 2019 to −2.2 (−4.4, 0.1) in 2022, followed by a recovery to −1.0 (−3.2, 1.4) in 2023. The lowest PFI values were observed among obese students (−4.9 in 2022). Eastern provinces showed higher baseline PFI but smaller declines, while western regions experienced sharper decreases (1.0 SD decline). BMI demonstrated an inverted–U relationship with PFI, showing a positive association within 18–25 kg/m 2 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.
Sun et al. (Mon,) studied this question.