TY - JOUR
T1 - US pediatric population-level associations of DXA-measured percentage of body fat with four BMI metrics with cutoffs
AU - Heo, M.
AU - Wylie-Rosett, J.
AU - Pietrobelli, A.
AU - Kabat, G. C.
AU - Rohan, T. E.
AU - Faith, M. S.
N1 - Funding Information:
This work was supported in part by Albert Einstein College of Medicine Funds, the Einstein Diabetes Research and Training Center P60 DK020541 and the Einstein-Montefiore Clinical and Translational Science Award UL1 RR025750
PY - 2014/1
Y1 - 2014/1
N2 - Objective:Four body mass index (BMI) metrics-BMI, BMI z-score, BMI percentile and BMI%-are commonly used as proxy measures for children's adiposity. We sought to determine a BMI metric that is most strongly associated with measured percentage of body fat (%BF) in the US pediatric population stratified by sex, age and race/ethnicity, and to determine cutoffs that maximize the association for each BMI metric.Subjects, Design and Methods:%BF was measured by dual-energy X-ray absorptiometry among N=6120 US boys and girls aged 8.0-17.9 years old from the National Health and Nutrition Examination Survey 1999-2004. We fit piecewise linear regression models with cutoffs to %BF data using each BMI metric as the predictor stratified by sex, race/ethnicity and age. The slopes were modeled differently before and after the cutoffs which were determined on the basis of grid searches.Results:BMI z-score was in general most strongly associated with %BF for both boys and girls. The associations of the four BMI metrics were lowest for boys aged 12-13.9 years and girls aged 16-17.9 years, and strongest for Mexican-American boys and for non-Hispanic Black girls. Overall, the associations were stronger for girls than for boys. In boys, BMI had the lowest association with %BF (R 2 =0.39) for all ages combined. The fold changes in slopes before and after cutoffs were greatest in general for BMI percentiles regardless of age, sex and race/ethnicity. BMI z-score cutoffs were 0.4 for both boys and girls for all ages combined. Except for BMI, the slopes after the cutoffs were in general greater than those before.Conclusions:All BMI metrics were strongly associated with %BF when stratified by age and race/ethnicity except that BMI was the least associated with %BF in boys for all ages combined. Overall, BMI z-score was superior for evaluation of %BF, and its cutoff of 0.4 can also serve as a threshold for careful monitoring of weight status.
AB - Objective:Four body mass index (BMI) metrics-BMI, BMI z-score, BMI percentile and BMI%-are commonly used as proxy measures for children's adiposity. We sought to determine a BMI metric that is most strongly associated with measured percentage of body fat (%BF) in the US pediatric population stratified by sex, age and race/ethnicity, and to determine cutoffs that maximize the association for each BMI metric.Subjects, Design and Methods:%BF was measured by dual-energy X-ray absorptiometry among N=6120 US boys and girls aged 8.0-17.9 years old from the National Health and Nutrition Examination Survey 1999-2004. We fit piecewise linear regression models with cutoffs to %BF data using each BMI metric as the predictor stratified by sex, race/ethnicity and age. The slopes were modeled differently before and after the cutoffs which were determined on the basis of grid searches.Results:BMI z-score was in general most strongly associated with %BF for both boys and girls. The associations of the four BMI metrics were lowest for boys aged 12-13.9 years and girls aged 16-17.9 years, and strongest for Mexican-American boys and for non-Hispanic Black girls. Overall, the associations were stronger for girls than for boys. In boys, BMI had the lowest association with %BF (R 2 =0.39) for all ages combined. The fold changes in slopes before and after cutoffs were greatest in general for BMI percentiles regardless of age, sex and race/ethnicity. BMI z-score cutoffs were 0.4 for both boys and girls for all ages combined. Except for BMI, the slopes after the cutoffs were in general greater than those before.Conclusions:All BMI metrics were strongly associated with %BF when stratified by age and race/ethnicity except that BMI was the least associated with %BF in boys for all ages combined. Overall, BMI z-score was superior for evaluation of %BF, and its cutoff of 0.4 can also serve as a threshold for careful monitoring of weight status.
KW - BMI metrics
KW - growth
KW - pediatric obesity
KW - percentage of body fat
UR - http://www.scopus.com/inward/record.url?scp=84891827276&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84891827276&partnerID=8YFLogxK
U2 - 10.1038/ijo.2013.134
DO - 10.1038/ijo.2013.134
M3 - Article
C2 - 23887060
AN - SCOPUS:84891827276
VL - 38
SP - 60
EP - 68
JO - International Journal of Obesity
JF - International Journal of Obesity
SN - 0307-0565
IS - 1
ER -