title: Comparison of methods to assess change in children's body composition.
abstract: BACKGROUND
  Little is known about how simpler and more available methods to measure change in body fatness compare with criterion methods such as dual-energy X-ray absorptiometry (DXA) in children.
  
  
  OBJECTIVE
  Our objective was to determine the ability of air-displacement plethysmography (ADP) and formulas based on triceps skinfold thickness (TSF) and bioelectrical impedance analysis (BIA) to estimate changes in body fat over time in children.
  
  
  METHODS
  Eighty-six nonoverweight and overweight boys (n = 34) and girls (n = 52) with an average age of 11.0 +/- 2.4 y underwent ADP, TSF measurement, BIA, and DXA to estimate body fatness at baseline and 1 +/- 0.3 y later. Recent equations were used to estimate percentage body fat by TSF measurement (Dezenberg equation) and by BIA (Suprasongsin and Lewy equations). Percentage body fat estimates by ADP, TSF measurement, and BIA were compared with those by DXA.
  
  
  RESULTS
  All methods were highly correlated with DXA (P < 0.001). No mean bias for estimates of percentage body fat change was found for ADP (Siri equation) compared with DXA for all subjects examined together, and agreement between body fat estimation by ADP and DXA did not vary with race or sex. Magnitude bias was present for ADP relative to DXA (P < 0.01). Estimates of change in percentage body fat were systematically overestimated by BIA equations (1.37 +/- 6.98%; P < 0.001). TSF accounted for only 13% of the variance in percentage body fat change.
  
  
  CONCLUSIONS
  Compared with DXA, there appears to be no noninvasive and simple method to measure changes in children's percentage body fat accurately and precisely, but ADP performed better than did TSF or BIA. ADP could prove useful for measuring changes in adiposity in children.
authors.affiliation: Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
authors.forename: Jane
authors.initials: J
authors.lastname: Elberg
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: McDuffie
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Sebring
authors.forename: Christine
authors.initials: C
authors.lastname: Salaita
authors.forename: Margaret
authors.initials: M
authors.lastname: Keil
authors.forename: Delphine
authors.initials: D
authors.lastname: Robotham
authors.forename: James C
authors.initials: JC
authors.lastname: Reynolds
authors.forename: Jack A
authors.initials: JA
authors.lastname: Yanovski
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods / Q000592:standards; D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000388:Air; D044383:Black People; D001823:Body Composition; D002648:Child; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity / Q000378:metabolism*; D010991:Plethysmography / Q000379:methods / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012885:Skinfold Thickness; D044465:White People