Abstract
Context. Waist circumference may offer improved diagnosis of obesity in youth compared with body mass index (BMI), but empirical evidence is limited. Objective. To compare the ability of BMI percentile using UK reference data and waist circumference percentile using UK reference data to diagnose high fat mass in English children. Design and Methods. In 7 722 9–10-year-olds (3 809 boys, 3 913 girls) sensitivity and specificity were calculated and receiver operator characteristic (ROC) analyses undertaken to determine the diagnostic accuracy of BMI and waist circumference z-scores to define high fat mass measured by dual energy x-ray absorptiometry (DXA). High fat mass was defined as being in the top decile of fatness for each sex (359 boys and 367 girls). Results. The area under the ROC curve was slightly higher for BMI percentile (0.92 in boys, 95% CI: 0.91 –0.93; 0.94 in girls, 95% CI: 0.93–0.95) than waist circumference percentile (0.89 in boys, 95% CI: 0.86–0.91; 0.81 in girls, 95% CI: 0.73–0.90). Specificity of BMI percentile was slightly but significantly higher than that of waist circumference percentile for both sexes (p<0.05 in each case). Conclusions. The present study suggests that waist circumference percentile has no advantage over BMI percentile for the diagnosis of high fat mass in children.
Acknowledgements
We are extremely grateful to all the families who took part in the study, the midwives for their help in recruiting them, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists and nurses. The UK Medical Research Council, the Wellcome Trust, and the University of Bristol provide core support for ALSPAC. Author contributions as follows. Original concept: JR. Study design: All authors. Statistical analyses: AD, NG, AS. Interpretation of data: All authors. Drafting of manuscript: JR. Critical review and rewriting of manuscript: All authors.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.