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).

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/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.

Keywords: BMI; Childhood obesity; Childhood overweight; Fast food consumption; International.

Figure 1

Flow of participants through the study. Children are represented in (A) and adolescents in (B) (BMI, body mass index).

Figure 2

Reported frequency of fast-food consumption by study participants. Children are represented in (A) and adolescents in (B).

Figure 3

The difference in body mass index (BMI) of study participants who consumed fast-food frequently and very frequently compared to infrequent fast-food consumption. Children are represented in (A) and adolescents in (B). For each country, the proportion of participants who consume fast-food frequently or very frequently is shown in parentheses. Those centres with reported height and weights are shown with filled-in circles, and those centres that measured heights and weights are shown with hollowed circles.