title: Changes in body mass index z score over the course of the academic year among children attending Head Start.
abstract: OBJECTIVE
  We tested the hypothesis that among 3- to 5-year-old children attending Head Start, body mass index z score will decline during the academic year and increase during the summer.
  
  
  METHODS
  We used retrospective longitudinal growth data collected over 5 academic years from 1914 children (51% boys, 62% white) enrolled in a Michigan Head Start program. Changes in body mass index (BMI) z score, calculated as annual rate of change, during 2 academic years and the intervening summer were assessed by piecewise linear regression analysis. Potential covariates were gender, single-parent status, program year, race/ethnicity, age at initial enrollment, and family income (divided by household size).
  
  
  RESULTS
  Mean BMI z score at the start of Head Start enrollment was 0.52 (95% confidence interval [95% CI] 0.39 to 0.65). Mean annual rates of BMI z score change were: -0.07 (95% CI -0.28 to 0.14) during the first year of enrollment, 0.62 (95% CI -0.0005 to 1.23) over the summer, and -0.82 (95% CI -1.50 to -0.13) during the second year of enrollment. The effect was most robust among girls of minority race/ethnicity.
  
  
  CONCLUSIONS
  Head Start is associated with a shifting of BMI z scores toward the norm among low-income preschool-aged children, particularly among girls of minority race/ethnicity.
authors.affiliation: Center for Human Growth and Development, University of Michigan, Ann Arbor, Michigan 48109-0406, USA. jlumeng@umich.edu
authors.forename: Julie C
authors.initials: JC
authors.lastname: Lumeng
authors.forename: Niko
authors.initials: N
authors.lastname: Kaciroti
authors.forename: David E
authors.initials: DE
authors.lastname: Frisvold
mesh_terms: D015992:Body Mass Index; D002675:Child, Preschool; D018479:Early Intervention, Educational; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D013997:Time Factors
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