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Body volume (BV), one component of a four-compartment (4C) body composition model, is commonly assessed using air displacement plethysmography (BodPod). However, dual-energy x-ray absorptiometry (DEXA) has been proposed as an alternative method for calculating BV. This investigation evaluated the validity and reliability of DEXA-derived BV measurement and a DEXA-derived 4C model (DEXA-4C) for percent body fat (%BF), fat mass (FM), and lean mass (LM). Using a total sample of 127 men and women, a traditional 4C body composition reference assessment was completed. A DEXA-4C model was created by linearly regressing BodPod BV with DEXA FM, LM, and bone mineral content as independent factors. The DEXA-4C model was validated in a random sub-sample of 27 subjects. Reliability was evaluated in a sample of 40 subjects that underwent a second session of identical testing.

Key Findings

  • When body volume derived from DEXA was applied to a 4C model, there were no significant differences in percent body fat, fat mass, or lean mass when compared to the traditional 4C model.
  • For body volume, percent body fat, fat mass, and lean mas relative consistency values ranged from 0.995 to 0.998. Standard error of measurement for body volume was 0.62 L, ranging from 0.831 to 0.960 kg. There were no significant differences between visits for percent body fat, fat mass, or lean mass.
  • The DEXA-4C model appears to be a valid and reliable method of estimating percent body fat, fat mass, and lean mass. The prediction of body volume from DEXA simplifies the acquisition of 4C body composition by eliminating the need for an additional body volume assessment.


  • Smith-Ryan AE, Mock MG, Ryan ED, Gerstner GR, Trexler ET, Hirsch KR. Validity and reliability of a 4-compartment body composition model using dual energy x-ray absorptiometry-derived body volume. Clin Nutr. 2016 May 15. pii: S0261-5614(16)30098-X. PMCID: PMC5110400.

Read More: Clinical Nutrition

Research Details

  • Research Center: University of North Carolina at Chapel Hill
  • Featured NORC Member(s): Abbie Smith-Ryan, PhD, CSCS, CISSN, Assistant Professor of Exercise and Sports Science
  • Center Contribution: This publication is directly related to Dr. Smith-Ryan’s P and F grant project.

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