PT - JOURNAL ARTICLE AU - Irene Braithwaite AU - Alistair W Stewart AU - Robert J Hancox AU - Richard Beasley AU - Rinki Murphy AU - Edwin A Mitchell AU - the ISAAC Phase Three Study Group TI - Fast-food consumption and body mass index in children and adolescents: an international cross-sectional study AID - 10.1136/bmjopen-2014-005813 DP - 2014 Dec 01 TA - BMJ Open PG - e005813 VI - 4 IP - 12 4099 - http://bmjopen.bmj.com/content/4/12/e005813.short 4100 - http://bmjopen.bmj.com/content/4/12/e005813.full SO - BMJ Open2014 Dec 01; 4 AB - Objective To investigate whether reported fast-food consumption over the previous year is associated with higher childhood or adolescent body mass index (BMI). Design Secondary analysis from a multicentre, multicountry cross-sectional study (International Study of Asthma and Allergies in Children (ISAAC) Phase Three). Subjects and 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/m2 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/m2 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/m2 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.