Endocrine Abstracts

Background: Over the last 60 years body composition of young people have changed towards increased fatness. Whole body fat percentage (%BF) derived from dual energy X-ray absorptiometry (DXA) scans are (although often not available) widely recognized as a better measure of fatness than BMI.

Objective: We aimed to provide reference materials for %BF of healthy Danish children evaluated by skinfold measurements and DXA and to compare sensitivity and specificity of different assessments of excess fatness.

Methods: Height, weight, and skinfolds, were measured in a large longitudinal cohort of Danish children from the Copenhagen area (n=2647.12792 examinations) between birth and 14 years. DXA scans were performed once at age 6–14 (n=1200). We calculated %BF from skinfold-measurements (Slaugther equation), evaluated number of overweight by BMI (Cole criteria) and evaluated increased fatness by DXA (using adult cut off values: males: 25%, females: 30%).

Results: Reference curves for %BF were constructed for boys and girls with generally higher values for girls and with broad intervals between +1S.D. and +2S.D. in both genders.

%BF from skinfolds were significantly lower (mean difference 13%) but correlated strongly (r=0.88) with DXA %BF, (and with similar Z-scores). BMI Z-score also correlated positively with DXA %BF (r=0.74), but a child with a normal BMI for gender and age (−1<BMI Z-score<1) could have a DXA %BF between 6 and 37. When applying adult cut off values for DXA %BF~1S.D. to identify children with excess fatness, only half of them were identified using BMI/Cole criteria (specificity of 99, but sensitivity of 50.5). Using %BF from skinfolds gave a specificity of 94.4 and sensitivity of 75.3.

Conclusions: Normal weight children may have too much fat. %BF derived from skinfolds measurements had a higher sensitivity than BMI when compared to the DXA when identifying children with excess fat.