[Weight-for-length index in evaluation of children's body weight status: a simple and accurate method].

This study examines the weight-for-length index (WLI)--weight/height/the WLI constant, where the WLI constant is the ratio between the 50th percentile weight and height for the age and sex--for its appropriateness in estimating the status of body weight among school children. The WLI constant has been calculated for practical use and rapid calculation. Using the known percentile data in the Taiwan area, this report shows evidence that the WLI constant has changed a little during the past 30 years. On theoretical grounds, it seems that the WLI is a valid index because it is independent of the progressing physical growth of children it Taiwan. Data were obtained for a sample of 5,214 healthy boys and 5,607 healthy girls ages 5 to 14, attending schools in Taipei, Taiwan. The WLI was found to be a satisfactory measure of relative weight as has been generally found for the body mass index (weight/height2) because it has little correlation with age (r = 0.07) and only a fair correlation with height (r = 0.26) for the whole sample of children. In an attempt to offer support for the findings, the relationship between WLI and the overweight index (actual weight/average weight for sex, age and height) were evaluated. The correlations between the WLI and the overweight index were excellent for each sex grouping (r = 0.91 for boys and 0.89 for girls). The results also suggest that the WLI appears to be a very accurate measure of obesity (sensitivity: 88.3-92.1%, specificity: 86.9-89.9%) for all the school children in this sample.(ABSTRACT TRUNCATED AT 250 WORDS)