Relative Fat Mass as an estimator of whole-body fat percentage among children and adolescents: A cross-sectional study using NHANES

• Published in: Scientific reports Vol. 9; no. 1; pp. 15279 - 14
• Main Authors: Woolcott, Orison O., Bergman, Richard N.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.10.2019; Nature Publishing Group
• Subjects: 692/308/3187; 692/699/2743/393; Absorptiometry, Photon; Adiposity - physiology; Adolescent; Adolescents; Age; Anthropometry; Body Composition - physiology; Body fat; Body height; Body Mass Index; Body weight; Child; Children; Children & youth; Cross-Sectional Studies; Dual energy X-ray absorptiometry; Female; Humanities and Social Sciences; Humans; Male; multidisciplinary; Nutrition Surveys; Obesity; Overweight; Science; Science (multidisciplinary); Sex; Sex Factors; Teenagers; Waist Circumference - physiology; Young Adult
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-51701-z

We evaluated the ability of the Relative Fat Mass (RFM) to estimate whole-body fat percentage among children and adolescents who participated in the National Health and Nutrition Examination Survey from 1999 through 2006 (n = 10,390). The RFM equation for adults (64 − (20 × height/waist circumference) + (12 × sex)) may be used for adolescents 15 to 19 years of age. For children and adolescents 8 to 14 years of age, we suggest a modified RFM equation, named as the RFMp (RFM pediatric): 74 − (22 × height/waist circumference) + (5 × sex). In both equations, sex equals 0 for boys and 1 for girls. RFMp was more accurate than BMI to estimate whole-body fat percentage (measured by dual energy X-ray absorptiometry, DXA) among girls (percentage of estimates that were <20% of measured body fat percentage, 88.2% vs. 85.7%; P = 0.027) and boys 8 to 14 years of age (83.4% vs. 71.0%; P < 0.001). RFM was more accurate than BMI among boys 15 to 19 years of age (82.3% vs. 73.9%; P < 0.001) but slightly less accurate among girls (89.0% vs. 92.6%; P = 0.002). Compared with BMI-for-age percentiles, RFMp had lower misclassification error of overweight or obesity (defined as a DXA-measured body fat percentage at the 85 th percentile or higher) among boys 8 to 14 years of age (6.5% vs. 7.9%; P = 0.018) but not girls (RFMp: 8.2%; BMI-for-age: 7.9%; P = 0.681). Misclassification error of overweight or obesity was similar for RFM and BMI-for-age percentiles among girls (RFM: 8.0%; BMI-for-age: 6.6%; P = 0.076) and boys 15 to 19 years of age (RFM: 6.9%; BMI-for-age: 7.8%; P = 0.11). RFMp for children and adolescents 8 to 14 years of age and RFM for adolescents 15 to 19 years of age were useful to estimate whole-body fat percentage and diagnose body fat-defined overweight or obesity.