title: Fast-food consumption and body mass index in children and adolescents: an international cross-sectional study.
abstract: OBJECTIVE
  To investigate whether reported fast-food consumption over the previous year is associated with higher childhood or adolescent body mass index (BMI).
  
  
  METHODS
  Secondary analysis from a multicentre, multicountry cross-sectional study (International Study of Asthma and Allergies in Children (ISAAC) Phase Three).
  
  
  METHODS
  Parents/guardians of children aged 6-7 completed questionnaires which included questions about their children's asthma and allergies, fast-food consumption, height and weight. Adolescents aged 13-14 completed the same questionnaire. The questionnaire asked "In the past 12 months, how often on average did you (your child) eat fast-food/burgers?" The responses were infrequent (never/only occasionally), frequent (once/twice a week) or very frequent (three or more times per week). A general linear mixed model was used to determine the association between BMI and fast-food consumption, adjusting for Gross National Income per capita by country, measurement type (whether heights/weights were reported or measured), age and sex.
  
  
  RESULTS
  72,900 children (17 countries) and 199,135 adolescents (36 countries) provided data. Frequent and very frequent fast-food consumption was reported in 23% and 4% of children, and 39% and 13% of adolescents, respectively. Children in the frequent and very frequent groups had a BMI that was 0.15 and 0.22 kg/m(2) higher than those in the infrequent group (p<0.001). Male adolescents in the frequent and very frequent groups had a BMI that was 0.14 and 0.28 kg/m(2) lower than those in the infrequent group (p<0.001). Female adolescents in the frequent and very frequent groups had a BMI that was 0.19 kg/m(2) lower than those in the infrequent group (p<0.001).
  
  
  CONCLUSIONS
  Reported fast-food consumption is high in childhood and increases in adolescence. Compared with infrequent fast-food consumption, frequent and very frequent consumption is associated with a higher BMI in children. Owing to residual confounding, reverse causation and likely misreporting, the reverse association observed in adolescents should be interpreted with caution.
authors.affiliation: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors.forename: Irene
authors.identifier: http://orcid.org/0000-0001-5327-3027
authors.initials: I
authors.lastname: Braithwaite
authors.affiliation: School of Population Health, The University of Auckland, Auckland, New Zealand.
authors.forename: Alistair W
authors.initials: AW
authors.lastname: Stewart
authors.affiliation: Department of Preventive & Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hancox
authors.affiliation: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors.forename: Richard
authors.initials: R
authors.lastname: Beasley
authors.affiliation: Faculty of Medicine and Health Sciences, Department of Medicine, The University of Auckland, Auckland, New Zealand.
authors.forename: Rinki
authors.initials: R
authors.lastname: Murphy
authors.affiliation: Faculty of Medicine and Health Sciences, Department of Paediatrics: Child and Youth Health, The University of Auckland, Auckland, New Zealand.
authors.forename: Edwin A
authors.initials: EA
authors.lastname: Mitchell
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D003430:Cross-Sectional Studies; D057140:Fast Foods / Q000009:adverse effects / Q000706:statistics & numerical data*; D005247:Feeding Behavior; D005260:Female; D005500:Follow-Up Studies; D014943:Global Health; D006801:Humans; D008297:Male; D009017:Morbidity / Q000639:trends; D009765:Obesity / Q000453:epidemiology*; D011159:Population Surveillance / Q000379:methods*; D012307:Risk Factors
keywords: BMI; Childhood obesity; Childhood overweight; Fast food consumption; International