title: Does early school entry prevent obesity among adolescent girls?
abstract: OBJECTIVE
  To examine the relationship between early school entry and body weight status among adolescent girls.
  
  
  METHODS
  Using nationally representative data from the 1997 cohort of the National Longitudinal Survey of Youth, we exploited state-specific first-grade entrance policy as a quasi-experimental research design to examine the effect of early school entry on the body weight status of adolescent girls. Fixed-effects models were used to compare the body mass index (BMI), BMI z-score, and likelihood of overweight and obesity between teenage girls born before school cut-off dates and those born after, while controlling for age, race/ethnicity, maternal education status, and maternal body weight status.
  
  
  RESULTS
  Late starters had higher BMIs and a higher prevalence of overweight and obesity and the results were found to be consistent across age groups. Among girls whose birthdays were within 1 month of the cut-off dates, the coefficient of late starting was significantly positive (β = .311; p = .02), indicating that it might be correlated with weight gain in adolescence.
  
  
  CONCLUSIONS
  Early admission to a school environment might have a long-term protective effect in terms of adolescent girls' propensity to obesity. Future studies are needed to examine the effect of early school entry on the eating behavior and physical activities of adolescent girls.
authors.affiliation: Department of Community and Preventive Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA. ning_zhang@urmc.rochester.edu
authors.forename: Ning
authors.initials: N
authors.lastname: Zhang
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D001835:Body Weight; D015331:Cohort Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D016015:Logistic Models; D009765:Obesity / Q000517:prevention & control*; D012574:Schools; D012959:Socioeconomic Factors