Objectives: Our goal was to compare BMI and waist circumference with dual-energy radiograph absorptiometry-based measures of adiposity and to describe the pattern and interrelations of these surrogate and direct adiposity measures in prepubertal and pubertal rural Chinese children.
Methods: This was a cross-sectional study of 2493 children aged 6 to 18 years from a population-based cohort of twin pairs. Dual-energy radiograph absorptiometry-based measurements included total body fat, percentage of body fat, trunk fat, and percentage of trunk fat. Age- and gender-specific patterns and interrelationships among BMI, waist circumference, and dual-energy radiograph absorptiometry-based measurements were described by using smoothing plots and age- and gender-specific correlation analyses.
Results: In girls, BMI, waist circumference, total body fat, percentage of body fat, trunk fat, and percentage of trunk fat all increased linearly with age. In boys, BMI and waist circumference increased linearly with age, but total body fat, percentage of body fat, and trunk fat did not increase significantly with age. In both genders, percentage of trunk fat reached a nadir around 12 years of age and then increased with age. Before puberty (6-11 years), BMI and waist circumference were correlated well with total body fat, percentage of body fat, and trunk fat in both genders. During puberty (12-18 years), the correlations between BMI and each of the dual-energy radiograph absorptiometry-based measurements were higher in girls than in boys. Similar trends were found in the correlations between waist circumference and each of the dual-energy radiograph absorptiometry-based measurements.
Conclusions: In this relatively lean rural Chinese population, BMI and waist circumference were highly correlated with each other and were good surrogates of total body fat, trunk fat, and percentage of body fat in prepubertal children of both genders and in pubertal girls. However, both BMI and waist circumference overestimated total and trunk fat, especially percentage of body fat in pubertal boys.