We sought to determine if the rate of increase in body mass index (BMI) differs between first generation immigrant children (child and both parents born outside Canada); second generation immigrant children (child born in Canada with at least one parent born outside Canada); and native-born children (child and both parents born in Canada), and if the rate of increase varies across ethnic groups.
Data were available from the evaluation of a 5-year heart health promotion program targeted to elementary school children from 24 schools in multi-ethnic, disadvantaged, inner-city neighborhoods in Montreal, Canada. Participants were 6392 children aged 9-12 years born in and outside of Canada. Height and weight were measured annually according to a standardized protocol. BMI increases with age were examined using individual growth models stratified by immigrant status grouping (first generation immigrant, second generation immigrant, native-born).
On average, BMI increased by 0.59, 0.73, and 0.82 kg/m2 with each year of age among first generation immigrant, second generation immigrant, and native-born children, respectively. These differences held across four family origin grouping (Europe, Asia, Central/South America, and Other).
The protective effect of immigrant status on BMI increases with age dissipated in second generation immigrant children, whose rate of increase was similar to that of native-born children. Because immigrants constitute the fastest growing segment of the Canadian population, it is important to understand the causes of the higher BMI increases with successive generations.