title: Comparison of percent body fat estimates using air displacement plethysmography and hydrodensitometry in adults and children.
abstract: OBJECTIVE
  The purpose of the study was to compare estimates of body density and percentage body fat from air displacement plethysmography (ADP) to those from hydrodensitometry (HD) in adults and children and to provide a review of similar recent studies.
  
  
  METHODS
  Body density and percentage body fat (% BF) were assessed by ADP and HD on the same day in 87 adults aged 18-69 y (41 males and 46 females) and 39 children aged 8-17 y (19 males and 20 females). Differences between measured and predicted thoracic gas volumes determined during the ADP procedure and the resultant effects of those differences on body composition estimates were also compared. In a subset of 50 individuals (31 adults and 19 children), reliability of ADP was measured and the relative ease or difficulty of ADP and HD were probed with a questionnaire.
  
  
  RESULTS
  The coefficient of reliability between %BF on day 1 and day 2 was 96.4 in adults and 90.1 in children, and the technical error of measurement of 1.6% in adults and 1.8% in children. Using a predicted rather than a measured thoracic gas volume did not significantly affect percentage body fat estimates in adults, but resulted in overestimates of percentage body fat in children. Mean percentage body fat from ADP was higher than percentage body fat from HD, although this was statistically significant only in adults (29.3 vs 27.7%, P<0.05). The 95% confidence interval of the between-method differences for all subjects was -7 to +9% body fat, and the root mean square error (r.m.s.e.) was approximately 4% body fat. In the subset of individuals who were asked to compare the two methods, 46 out of 50 (92%) indicated that they preferred the ADP to HD.
  
  
  CONCLUSIONS
  ADP is a reliable method of measuring body composition that subjects found preferable to underwater weighing. However, as shown here and in most other studies, there are differences in percentage body fat estimates assessed by the two methods, perhaps related to body size, age or other factors, that are sufficient to preclude ADP from being used interchangeably with underwater weighing on an individual basis.
authors.affiliation: Lifespan Health Research Center, Department of Community Health, Wright State University School of Medicine, Kettering, Ohio 45420, USA. ellen.demerath@wright.edu
authors.forename: E W
authors.initials: EW
authors.lastname: Demerath
authors.forename: S S
authors.initials: SS
authors.lastname: Guo
authors.forename: W C
authors.initials: WC
authors.lastname: Chumlea
authors.forename: B
authors.initials: B
authors.lastname: Towne
authors.forename: A F
authors.initials: AF
authors.lastname: Roche
authors.forename: R M
authors.initials: RM
authors.lastname: Siervogel
mesh_terms: D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D000368:Aged; D000388:Air; D001823:Body Composition; D002648:Child; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D010991:Plethysmography; D012115:Residual Volume; D012680:Sensitivity and Specificity; D014867:Water
chemical_list: D014867:Water