Comparison of Weight for Height and BMI for Age for Estimating Overnutrition Burden in Under-Five Populations With High Stunting Prevalence

ABSTRACT

Background: Overnourished under-five children are anthropometrically classified as either being at possible risk of overweight, overweight or obese and defined so, when either weight for height or body mass index for age (BMI-for-age) are >1SD to 2SD, >2SD to 3SD and >3SD, respectively of the analogous World Health Organization standards. Aim: To compare weight for height and BMI for age definitions for quantifying overnutrition burden. Methods: Theoretical consequences of ignoring age were evaluated by comparing, at varying height for age z-scores, the age- and sex-specific cutoffs of BMI that would define overnutrition with these two metrics. Overnutrition prevalence was then compared in simulated populations (short, intermediate and tall) and real-life datasets from India. Results: In short (-2SD) children, the BMI cutoffs with weight for height criteria were lower in comparison to BMI for age till 7-8 months, but higher at later ages. In National Family Health Survey-4, India dataset (short population), overnutrition (>1SD) prevalence with weight for height was higher from 0-0.5 years (exclusive breastfeeding age), but lower at subsequent ages. The prevalence difference (weight for height - BMI for age) in 0.5-5 years was -2.26% (6.57% vs 8.83%); this attenuated in 0-5 years (-1.55%; 7.23% vs 8.78%). The discrepancy was maximal for stunted children and was lower in girls. A similar pattern, of lower magnitude, was observed for overweight (>2SD) comparison. In intermediate and tall populations, there were no meaningful differences. Conclusion: The two definitions produce cutoffs, and hence estimates of overnutrition, that differ with the age, sex, and height of under-five children. The relative invariance, with age and height, of BMI for age, favors its use.