title: Determinants of moderate to vigorous physical activity and obesity in children: a structural equation modeling analysis.
abstract: BACKGROUND
  The determinants of physical activity (PA) and body fatness in Chinese adolescents are rarely examined. This study aimed to investigate the effect of attitude toward PA, screen time, parents' socioeconomic status (SES), and exercise habit on PA and body fatness among Chinese children by using structural equation modeling (SEM) analysis.
  
  
  METHODS
  Data obtained from the second Community Fitness Survey in Hong Kong were utilized, in which students from one secondary school of each of the 18 districts of Hong Kong were recruited. A total of 2517 questionnaires with physical fitness items were successfully distributed to students aged 13-19 years in these districts. Families' SES, parents' exercise habit, children's intention to participate in PA, amount of moderate to vigorous PA (MVPA), screen time, children's attitude toward PA, and children's body fat percentage were measured and analyzed with SEM. The structural equation model was composed of a measurement model and a structural model. The model was tested with Mplus 6. The Chi-square test, root mean square error of approximation, comparative fit index, and Tucker-Lewis index were calculated to evaluate model fit. The model was then modified based on the model fit indices.
  
  
  RESULTS
  Children's intention to participate in PA was a strong predictor of their engagement in MVPA. Parents' exercise habit had both direct and indirect (via attitude) effects on their children's intention to participate in PA. Screen time was not a predictor of body composition. Children's intention to participate in PA directly affected their body composition. Children's attitude toward PA, parents' exercise habit, and SES had significant effects on the children's intention to participate in PA. Furthermore, obesity had a negative effect on the children's attitude toward PA.
  
  
  CONCLUSIONS
  To promote MVPA and prevent obesity in Chinese children of Hong Kong, it is important to design intervention that enhances children's intention and attitude in PA, as well as parent's exercise habits. Tailormade programs that take SES into consideration are also essential. Further studies are necessary to extend the results and test the model in other metropolitan areas in China.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Indiana University, Indiana, USA.
authors.forename: Daniel Chi-Shing
authors.initials: DC
authors.lastname: Yeung
authors.affiliation: Department of Counseling and Educational Psychology, School of Education, Indiana University, Indiana, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Sports Science and Physical Education, The Chinese University of Hong Kong, Shatin, Hong Kong, China. hui2162@cuhk.edu.hk.
authors.forename: Stanley Sai-Chuen
authors.initials: SS
authors.lastname: Hui
authors.affiliation: School of Health Systems and Public Health, Biostatistics and Epidemiology, Faculty of Medicine, University of Pretoria, Pretoria, South Africa.
authors.forename: Shingairai Aliifina
authors.initials: SA
authors.lastname: Feresu
mesh_terms: D000293:Adolescent; D001290:Attitude; D003201:Computers; D015444:Exercise; D005260:Female; D006723:Hong Kong; D006801:Humans; D008297:Male; D015233:Models, Statistical; D063766:Pediatric Obesity / Q000453:epidemiology*; D012959:Socioeconomic Factors; D013690:Television; D013997:Time Factors
keywords: adolescent obesity; behavior; childhood obesity; physical activity; socioeconomic factors