Elsevier

Preventive Medicine

Volume 52, Issue 2, 1 February 2011, Pages 109-113
Preventive Medicine

Physical activity, cardiorespiratory fitness, and obesity among Chinese children

https://doi.org/10.1016/j.ypmed.2010.11.005Get rights and content

Abstract

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/m2 change in BMI during the follow-up period (β =  0.63 kg/m2 and − 0.64 kg/m2 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.

Introduction

A rising prevalence of childhood obesity has been seen worldwide (Haslam et al., 2006). Childhood obesity can result in adverse health consequences, including cardiovascular disease (CVD) and type 2 diabetes (Perez Gomez and Huffman, 2008). It may persist into adulthood, which is associated with increased morbidity and mortality (McMillan et al., 2006). It is therefore vital to understand the risk factors for childhood obesity.

Among numerous factors which may contribute to childhood obesity, physical activity (PA) and cardiorespiratory fitness (CRF) are of particular interest. Several studies have suggested that high CRF might attenuate the health risks attributed to obesity in children (Rizzo et al., 2007), and adolescents (Flouris et al., 2007). Also, there is evidence that decreased PA is associated with obesity, whereas physically active children may have lower risks of chronic diseases than physically inactive children (Dugan, 2008). However, activity-related energy expenditure at baseline has not been found to predict increasing adiposity (Johnson et al., 2000), and other researchers failed to show associations between adolescent CRF and adult cholesterol, blood pressure, and glucose levels (Eisenmann et al., 2005). Furthermore, it remains controversial as to whether a gender difference exists since some researchers reported a significant relationship between CRF and/or PA and body composition only in girls (Mota et al., 2006, Kim et al., 2005).

A better understanding of the association between PA, CRF and childhood obesity is important in assessing the benefits of intervention programs aimed at preventing obesity. However, most previous investigations have been cross-sectional in design (Mota et al., 2006, Ara et al., 2007, Hussey et al., 2007, Stratton et al., 2007), while the limited longitudinal studies were predominately limited to Caucasian populations, and did not account for the influence of PA on body weight (Kim et al., 2005, McGavock et al., 2009, Mota et al., 2009). No studies that address this issue among Chinese children have been reported. China has undergone enormous socioeconomic changes in the past three decades. One consequence is that the prevalence of overweight/obesity is approaching that of the developed countries. A recent Chinese national survey has revealed that the overall prevalence of obesity and overweight in children aged under 7-year old was 7.2% and 19.8%, with an annual rate of increase of 156% and 52% for obesity and overweight, respectively (Ding, 2008). In this study, we aimed to examine the relationships between PA, CRF and obesity in Chinese children, and determine whether PA and CRF affected the changes in body composition over time in a cohort of school children.

Section snippets

Subjects and data collection

We analyzed data from a prospective cohort study on air pollution and cardiorespiratory health in Guangzhou, China. The study design and methods have been previously described (He et al., 2008). Briefly, children from one to four primary schools in three districts were recruited. Schools were chosen based on their proximity to the local air monitoring stations and the required sample size in the main study. The baseline study (T1) was conducted from September to November 2006. After 18 months,

Results

Of 2179 children who participated in the baseline study, 352 were lost to follow-up, 32 did not complete the CRF test in the second survey. The remaining 1795 (82.4%) children (901 boys and 894 girls; mean age: 10.2, SD: 0.8) provided CRF data in both surveys. They had similar age, height, and PA status with those lost to follow up, but there were more girls, and the children were significantly heavier, with higher BMI and lower CRF. There were only 4.5% and 2.1% missing values for PA in T1 and

Discussion

In this paper we examined prospectively the relationship of CRF and PA with childhood obesity in 1795 Chinese schoolchildren. The main finding was that, regardless of gender, CRF was significantly inversely associated with subsequent body weight gain over an 18-month period. In addition, boys with low CRF had significantly increased risks of becoming or remaining overweight or obese. Although PA had no direct effects on BMI, active children showed significantly higher CRF than inactive children.

Conflict of interest statement

The authors declare that there are no conflicts of interest.

Acknowledgments

We thank Prof. Wilson Tam and Dr. Xin Gao for their excellent technical assistance. We are also very grateful to the students, their parents, the schools' principals and their teachers who participated in this study, and all of the field investigators.

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