Physical activity, cardiorespiratory fitness, and obesity among Chinese children.

Objective: To investigate the relationships of cardiorespiratory fitness (CRF) and physical activity (PA) with the risk of overweight/obesity in Chinese schoolchildren.

Methods: A total of 1795 children aged 8-13 years at baseline were followed-up for 18 months from 2006 to 2008 in Guangzhou, China. Children were categorized as "normal weight", "overweight", and "obese" using Chinese obesity cut-off points. Data on self-reported PA were obtained. CRF was determined by the 20-meter multistage fitness test, and the sex-specific median values were set as the cut-off points for the classification of high and low CRF.

Results: Significantly higher CRF was found in children with normal weight (from 6.55 to 8.65 ml/kg/min) or physically active children (from 0.42 to 1.22 ml/kg/min) compared with the reference group. CRF was inversely associated with the kg/m(2) change in BMI during the follow-up period (β=-0.63 kg/m(2) and -0.64 kg/m(2) for boys and girls, respectively, both p<0.001). Significant association of baseline CRF with overweight/obesity was found in boys (odds ratio (OR) 8.71; 95% confidence interval (CI) 2.59-29.26, p<0.001), whereas the association was marginally insignificant in girls (OR 6.87; 95% CI 0.96-49.09, p=0.055).

Conclusions: The results showed a strong negative association between CRF levels and children's BMI and weight gain.