Secular trends in the body mass index of Canadian children.

TLDR

Societal shifts toward sedentary lifestyles and high‑kilojoule diets may drive a progressive increase in body mass over time. This study examined secular changes in BMI among Canadian children aged 7‑13 years between 1981 and 1996 using nationally representative surveys. Regression analyses of BMI on age were applied to 1981, 1988, and 1996 survey data to assess population changes and distribution shifts in children. BMI rose by about 0.1 kg/m² per year, with overweight prevalence increasing from 15 % to 28.8 % in boys and 15 % to 23.6 % in girls, and obesity more than doubling from 5 % to 13.5 % in boys and 11.8 % to 23.6 % in girls, indicating a clear secular trend toward higher BMI.

Abstract

Various changes in society have created the opportunity for more sedentary behaviour and the consumption of food that is high in kilojoules, which may lead to a progressive increase in body mass over time. The purpose of this study was to examine secular changes in the body mass index (BMI) of Canadian children between 1981 and 1996.Nationally representative data from the 1981 Canada Fitness Survey, the 1988 Campbell's Survey on the Well-being of Canadians and the 1996 National Longitudinal Survey of Children and Youth were used in the analysis. Regression analyses were used to assess population changes in BMI from 1981 to 1996 for children aged 7-13 years. Changes in the distribution of BMI results were evaluated by plotting the residuals from regression analyses of BMI on age, assessed separately by sex, using the 1981 data as baseline. The proportions of children exceeding the 85th and 95th age- and sex-specific percentiles from the 1981 (baseline) data were also calculated.Since 1981, BMI has increased at the rate of nearly 0.1 kg/m2 per year for both sexes at most ages, indicating a clear secular trend toward an increase in BMI of Canadian children. The prevalence of overweight among boys increased from 15% in 1981 to 28.8% in 1996 and among girls from 15% to 23.6%. The prevalence of obesity in children more than doubled over that period, from 5% to 13.5% for boys and 11.8% for girls.Secular trends indicate that Canadian children aged 7-13 years are becoming progressively overweight and obese.