Changes in Physical Activity Patterns and Dietary Intake in Chinese Youth and their Associations with Obesity: A Longitudinal Study in Nanjing City, China
Authors: Chang Huiru , Xu Fei , Xue Hong , Wang Youfa 
Published: November 2023

Objectives

The prevalence of childhood overweight and obesity has increased rapidly in China over the past two decades, and is most pervasive in urban areas. However, studies that examine changes in energy balance‐related behaviors remain limited for Chinese children. This study aimed to: 1) study the current physical activity (PA) patterns and dietary intake in Chinese school children and the changes over a one year follow‐up period; 2) examine the relationship between the changes in PA and dietary intake and the changes in children's body mass index z‐score (BMI‐z) and weight status; 3) assess the potential gender differences related to the changes in the PA and dietary intake, and the relationship between these changes and child weight outcome.

Methods

A longitudinal study was conducted using the data from the Childhood Obesity Prevention Project in Nanjing, China from 2013 to 2014. Data was collected from 32 primary and 16 junior high schools recruited randomly from 8 urban districts. The data set is comprised of 10,091 children in grades four and seven. Student t‐test, Chi‐square test and ANOVA were applied to examine the PA patterns, dietary intake and related changes. Mixed linear and logistic models were fitted to assess the associations between the PA and dietary behaviors and children's BMI‐z and weight status.

Results

Regarding baseline PA, 7th graders had significantly lower PA level measured by MET min/week (4th vs. 7th grader: 5526±6622 vs. 3660±5700 MET.min/wk; p<0.01) and shorter sleep duration (4th vs. 7th grader: 9.3±2.8 vs. 8.5±2.1 hr./d; p<0.01). There were great sex differences at baseline in soft drink intake (girls vs. boys=1.1±2.3 vs. 1.7±2.2 time/wk; p<0.01) and screen time (girls vs. boys=197±339 vs. 290±539 min/wk). Over the follow‐up year, participating children had 134±6803 MET.min/wk (p<0.05) decrease in PA level, 0.3±2.8 hr./d (p<0.01) decrease in sleep duration and 0.18±0.56 (p<0.01) increase in BMI‐z. The prevalence of overweight and obesity was 33.3% (23.9% girls and 41.7% boys respectively) at baseline in the children enrolled. The prevalence increased by 3.0% (p<0.01) in one year with an increase in girls and boys of 4.1% and 2.0% respectively. In the adjusted mixed model, active commuting to and from school showed a strong positive association with PA level (β (SE)=429.8(120.5); p<0.01). Screen time was positively associated with children's BMI‐z (β (SE)=0.011(0.002); p<0.01), while the sleep duration was adversely associated with children's BMI‐z (β (SE)= −0.015(0.006); p<0.05).

Conclusions

The decreased PA level and sleep duration are associated with higher BMI‐z score among the recruited children and may provide some explanation for the increasing rate of childhood obesity in China. The dietary intake and PA patterns described by the study may inform interventions and research that is designed to increase PA level and prevent obesity in school children.

Support or Funding Information Funding: NIH U54 center grant, HD070725.