Background: The 2000 Centers for Disease Control and Prevention growth charts for the United States include population reference data for body mass index (BMI)-for-age (ages 2-19 y) and weight-for-stature (from 77 to 121 cm). For younger children, either set of reference data could be used.
Objective: The objective of this study was to compare BMI-for-age with weight-for-stature.
Design: We used data for 4348 children (aged 2-5 y) from the third National Health and Nutrition Examination Survey. Weight-for-stature and BMI-for-age percentiles were calculated for each child. The 10th and 85th percentiles of weight-for-stature at selected ages were also reexpressed as BMI-for-age percentiles.
Results: More than 63% of children had lower weight-for-stature than BMI-for-age percentiles. Children were more likely to be classified as < or = 10th percentile by weight-for-stature than by BMI-for-age, but less likely to be classified as > or = 85th percentile. Differences in classification by the 2 measures varied with age and stature and were greater for shorter children. The 10th and 85th percentiles of weight-for-stature corresponded to BMI-for-age percentiles from the 3rd to the 21st percentile and from the 74th to the 92nd percentile, respectively, depending on age and stature.
Conclusions: Weight-for-stature is easier to use than BMI-for-age. However, BMI-for-age captures changes in the weight-height relation with age and can be used continuously up to the age of 20 y. BMI-for-age is recommended in most situations. BMI-for-age and weight-for-stature will not give identical results and are not interchangeable.