title: Summer effects on body mass index (BMI) gain and growth patterns of American Indian children from kindergarten to first grade: a prospective study.
abstract: BACKGROUND
  Overweight and obesity are highly prevalent among American Indian children, especially those living on reservations. There is little scientific evidence about the effects of summer vacation on obesity development in children. The purpose of this study was to investigate the effects of summer vacation between kindergarten and first grade on growth in height, weight, and body mass index (BMI) for a sample of American Indian children.
  
  
  METHODS
  Children had their height and weight measured in four rounds of data collection (yielded three intervals: kindergarten, summer vacation, and first grade) as part of a school-based obesity prevention trial (Bright Start) in a Northern Plains Indian Reservation. Demographic variables were collected at baseline from parent surveys. Growth velocities (Z-score units/year) for BMI, weight, and height were estimated and compared for each interval using generalized linear mixed models.
  
  
  RESULTS
  The children were taller and heavier than median of same age counterparts. Height Z-scores were positively associated with increasing weight status category. The mean weight velocity during summer was significantly less than during the school year. More rapid growth velocity in height during summer than during school year was observed. Obese children gained less adjusted-BMI in the first grade after gaining more than their counterparts during the previous two intervals. No statistically significant interval effects were found for height and BMI velocities.
  
  
  CONCLUSIONS
  There was no indication of a significant summer effect on children's BMI. Rather than seasonal or school-related patterns, the predominant pattern indicated by weight-Z and BMI-Z velocities might be related to age or maturation.
  
  
  BACKGROUND
  Bright Start: Obesity Prevention in American Indian Children Clinical Trial Govt ID# NCT00123032.
authors.affiliation: Division of Epidemiology and Community Health, School of, Public Health, University of Minnesota, 1300 South 2nd Street, Suite 300, Minneapolis, MN 55454, USA. jd_zh@mail.hust.edu.cn
authors.forename: Jianduan
authors.initials: J
authors.lastname: Zhang
authors.forename: John H
authors.initials: JH
authors.lastname: Himes
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hannan
authors.forename: Chrisa
authors.initials: C
authors.lastname: Arcan
authors.forename: Mary
authors.initials: M
authors.lastname: Smyth
authors.forename: Bonnie Holy
authors.initials: BH
authors.lastname: Rock
authors.forename: Mary
authors.initials: M
authors.lastname: Story
mesh_terms: D015992:Body Mass Index; D001835:Body Weight / Q000208:ethnology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007198:Indians, North American; D008297:Male; D008910:Minnesota; D011446:Prospective Studies; D012621:Seasons; D015430:Weight Gain / Q000208:ethnology*