Supplementary file 1_Secular trends in physical fitness and nutritional status among Tibetan children and adolescents from 2005 to 2019: a secondary analysis of four CNSSCH surveys.docx

Additionally, generalized additive models (GAMs) were used to assess the associations between PFI and adverse nutritional status (thinness, overweight, and obesity), with results expressed as odds ratios (ORs).</p>Results<p>From 2005 to 2019, the PFI increased by 4.91 units among Tibetan children and adolescents, accompanied by an initial increase followed by a decline in the proportion of thinness, whereas overweight/obesity increased over the study period.

Fractional polynomial regression revealed an inverted U-shaped association between BMI Z-score and PFI, with physical fitness being lower in children and adolescents with thinness or overweight/obesity than in those with normal weight. Further analyses based on prevalence and ORs showed that, as PFI decreased, the prevalence and odds of thinness increased more sharply than those of overweight/obesity. Using PFI values of −5 and 5 as representative examples, the estimated ORs for thinness at PFI = −5 ranged from 1.53 to 1.88 across survey years, whereas the corresponding ORs for overweight/obesity ranged from 1.10 to 1.75; at PFI = 5, the corresponding ORs declined to 0.16–0.43 for thinness and 0.49–0.90 for overweight/obesity.</p>Conclusion<p>Although physical fitness improved among Tibetan children and adolescents over the study period, both thinness and overweight/obesity were associated with less favorable physical fitness.

These findings suggest that maintaining an appropriate weight status may be important for promoting favorable physical fitness development among children and adolescents.</p>