title: Excessive homework, inadequate sleep, physical inactivity and screen viewing time are major contributors to high paediatric obesity.
abstract: OBJECTIVE
  This study examined the relationships between energy balance-related behaviours (EBRBs) outside school hours and obesity in Chinese primary school students. We also explored the influence of gender on those relationships.
  
  
  METHODS
  The study sample was a cross-sectional cohort of 5032 Chinese children who were enrolled in grades 1-6 in primary schools in five Chinese cities and whose mean ages ranged from seven years and three months to 11.9 years. The children's parents completed a survey on their child's height, weight and EBRBs outside school hours.
  
  
  RESULTS
  The response rate was 97%, and the reported rates of overweight and obesity were 13.6% and 13.8%, respectively. The obesity rates were higher in boys and lower grade children. Most EBRBs varied between boys and girls and with increased grade levels. The amount of time spent on academic-related activities, screen viewing, outdoor activities and sleep was mostly associated with obesity on weekdays and varied by gender.
  
  
  CONCLUSIONS
  Rate of obesity was alarmingly high in the primary school Chinese children in this cohort, especially in younger children. Excessive time spent on academic-related activities outside school hours, inadequate sleep, physical inactivity and higher levels of screen viewing were major contributors to obesity in these Chinese children.
authors.affiliation: School of Sport Sciences, Beijing Sport University, Beijing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Ren
authors.affiliation: School of Physical Education and Coaching Science, Capital University of Physical Education and Sports, Beijing, China.
authors.forename: Zhixiong
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA.
authors.forename: Wenxi Kevin
authors.initials: WK
authors.lastname: Liu
authors.affiliation: Children's Center of China, Beijing, China.
authors.forename: Xiujiang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA.
authors.forename: Zenong
authors.initials: Z
authors.lastname: Yin
mesh_terms: D002648:Child; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003479:Curriculum; D015444:Exercise; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D063766:Pediatric Obesity / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D011998:Recreation; D012307:Risk Factors; D057185:Sedentary Behavior; D012737:Sex Factors; D012892:Sleep Deprivation; D013690:Television / Q000706:statistics & numerical data*; D013997:Time Factors; D018910:Video Games / Q000706:statistics & numerical data
keywords: Energy balance-related behaviours; Homework; Obesity; Outdoor activities; Screen viewing