Body fat throughout childhood in 2647 healthy Danish children: agreement of BMI, waist circumference, skinfolds with dual X-ray absorptiometry

Abstract

Total body fat percentage (%BF) evaluated by dual energy X-ray absorptiometry (DXA) scans (DXA %BF) is widely recognized as a precise measure of fatness. We aimed to establish national reference curves for DXA %BF, %BF calculated from skinfolds (SF %BF) and waist circumference (WC) in healthy children, and to compare agreement between the different methods. Based on 11 481 physical examinations (anthropometry) and 1200 DXA scans from a longitudinal cohort of Danish children (n=2647), we established reference curves (LMS-method) for SF %BF, WC (birth to 14 years) and DXA %BF (8-14 years). Age- and sex-specific Z-scores for body mass index (BMI), WC and SF %BF were compared. Sensitivity and specificity were calculated for agreement of WC, SF %BF and BMI with DXA %BF to identify obese children (>+1 s.d.). %BF differed with age, sex, pubertal stage and social class. SF %BF correlated strongly with DXA %BF (r=0.86). BMI and WC also correlated positively with DXA %BF (Z-scores; r= 0.78 and 0.69). Sensitivity and specificity were 79.5 and 93.8 for SF %BF, 75.9 and 90.3 for BMI and 59.2 and 95.4 for WC. SF %BF showed the highest correlation and best agreement with DXA %BF in identifying children with excess fat (+1 s.d.).