title: Sex differences in obesity incidence: 20-year prospective cohort in South Africa.
abstract: BACKGROUND
  Prospective data spanning childhood and adolescence are needed to better understand obesity incidence among children and to identify important periods for intervention.
  
  
  OBJECTIVE
  To describe gender differences in overweight and obesity from infancy to late adolescence in a South African cohort.
  
  
  METHODS
  We analysed body mass index at 1-2 years, 4-8 years, 11-12 years, 13-15 years and 16-18 years among 1172 participants in the South African Birth-to-Twenty cohort.
  
  
  RESULTS
  Among boys, overweight and obesity prevalence declined from age 1-2 years to 16-18 years. Among girls, overweight and obesity prevalence increased from 4-8 years to 16-18 years. Obesity incidence was highest from 4-8 years to 11-12 years in boys (6.8 cases per 1000 person-years) and from 11-12 years to 13-15 years in girls (11.2 cases per 1000 person-years). Among girls, obesity at 16-18 years was associated with overweight (odds ratio [OR] = 3.6; 95% confidence interval [CI] 1.8-7.2) or obesity (OR = 8.0; 95% CI 3.7-17.6) at 1-2 years and overweight (OR = 6.8; 95% CI 3.3-13.9) or obesity (OR = 42.3; 95% CI 15.0-118.8) at 4-8 years; for boys, obesity at 16-18 years was associated with overweight at 1-2 years (OR = 5.6; 95% CI 1.7-18.0) and obesity at 4-8 years (OR = 19.7; 95% CI 5.1-75.9).
  
  
  CONCLUSIONS
  Among girls, overweight and obesity increased throughout childhood. Overweight and obesity were not widely prevalent among boys. Early childhood and post-puberty may be important periods for intervention among girls.
authors.affiliation: Nutrition and Health Sciences Program, Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, GA, USA.|Medical Research Council (MRC) Developmental Pathways for Health Research Unit, University of Witwatersrand, Johannesburg, South Africa.
authors.forename: E A
authors.initials: EA
authors.lastname: Lundeen
authors.affiliation: Medical Research Council (MRC) Developmental Pathways for Health Research Unit, University of Witwatersrand, Johannesburg, South Africa.
authors.forename: S A
authors.initials: SA
authors.lastname: Norris
authors.affiliation: Medical Research Council (MRC) Developmental Pathways for Health Research Unit, University of Witwatersrand, Johannesburg, South Africa.|Gillings School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Adair
authors.affiliation: Medical Research Council (MRC) Developmental Pathways for Health Research Unit, University of Witwatersrand, Johannesburg, South Africa.|Human Sciences Research Council, Durban, South Africa.
authors.forename: L M
authors.initials: LM
authors.lastname: Richter
authors.affiliation: Medical Research Council (MRC) Developmental Pathways for Health Research Unit, University of Witwatersrand, Johannesburg, South Africa.|Rollins School of Public Health, Hubert Department of Global Health, Emory University, Atlanta, GA, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Stein
mesh_terms: D000293:Adolescent; D044383:Black People / Q000706:statistics & numerical data*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009765:Obesity / Q000453:epidemiology*; D016017:Odds Ratio; D015995:Prevalence; D011446:Prospective Studies; D012727:Sex Characteristics; D013019:South Africa / Q000453:epidemiology
keywords: Body mass index; child growth; childhood overweight and obesity