Association of waist circumference and body mass index with fasting blood insulin in severely obese children: A cross-sectional study

We tested whether body mass index (BMI) and waist circumference (WC) are associated with fasting insulin in severely obese children. A number of 391 (204 female and 187 male) obese children were consecutively enrolled in the study at a Paediatric outpatient clinic. They were aged 10±3 yr (mean±SD; range: 3-17 yr) and had a relative weight for age of 160±27% (mean±SD). BMI and WC explained respectively 9 and 13% of the variance of log-transformed (It) insulin (p<O.OOOI for both). After correction for age, however, BMI lost its association with It-insulin (p=NS) and WC explained only 3% (p<0.001) of It-insulin variance. Sex and pubertal status did not influence the relationship between WC, BMI and It-insulin (p=NS, ANCOVA). We conclude that in severely obese children: 1) WC is a marginaUy better predictor of fasting blood insulin than BMI, 2) age has a substantial influence on the relationship between BMI, WC and insulin and, 3) the contribution of BMI and WC to insulin is of doubtful clinical relevance because it leaves a substantial portion (~87%) of It-insulin variance unexplained