Tracking of body mass indices over 2 years in Māori and European children

In 2002, the prevalence of overweight and obesity, defined by body mass index (BMI), was higher in New Zealand Māori (40%) and Pacific (60%) than in European (24%) children; however, this does not take into account interethnic differences in body composition. This study compared trajectories of anthropometric indices from 2004 to 2006 among 5- and 10-year-old Māori and European children.

In 2004 and then in 2006, 1244 children (639 boys and 605 girls) aged 5 and 10 years had height, weight and fat-free mass (FFM) by bioimpedance measured to derive measures of fat mass (FM), percentage body fat (%BF), FM index (FMI, FM/height(2)), FFM index (FFMI, FFM/height(2)), and s.d. scores for BMI and %BF and BMI categories by International Obesity Task Force criteria.

Body composition and growth in Māori children is different from European children. Over 2 years, the BMI and %BF s.d. scores in both 5- and 10-year-old cohorts increased more in Māori children than in European children. The prevalence of overweight and obesity also increased within ethnicity and age group. The relative change of FMI and FFMI differed by age group, gender and ethnicity. In Māori girls, the magnitude of the changes between 10 and 12 years of age was most marked-the major contribution was from an increase in FMI. At 12 years, the mean %BF of Māori girls was 31.7% (95% confidence interval (CI): 30.1 and 33.3) compared with that of European girls (28.0%; 95% CI: 27.0 and 29.0).

FM and FFM measures provide a more appropriate understanding of growth and body composition change in children than BMI, and vary with gender and ethnicity. Thus, FMI and FFMI should be tracked and compared among populations.