Correspondence between waist-to-height ratio and body mass index in juniors

Despite the increase in body mass through childhood and adolescence is countered by the increase in height in the Body Mass Index (BMI), this measure is inadequate for judging the degree of excess weight among the young. Unlike using clearly defined cut points, same for any stage of adulthood, it is required to consult BMI-for-age charts, which can be a demanding exercise when data analysis is involved. The waist circumference to height ratio (WCHR) was hypothesised to be invariant to age change, and this is generally supported by the epidemiological evidence. This paper analyses a sample of NHANES data to find a connection between BMI, WCHR and Age. A strong linearity between the anthropometric measures is demonstrated, thus enabling estimation of WCHR for a given BMI and Age. The pattern of change of this parameter at BMI levels that indicate the transition to overweight state or obesity thus becomes unravelled. The results strongly support the feasibility of a universal WCHR threshold for the overweight state past early childhood and through adolescence, and the estimated one is similar to the WCHR levels found elsewhere in the literature.