Objective: To examine the differences arising from indexing resting metabolic rate (RMR) against fat-free mass (FFM) determined using two-, three- and four-compartment body composition models. Design: All RMR and body composition measurements were conducted on the same day for each subject following compliance with premeasurement protocols. Subjects: Data were generated from measurements on 104 males (age 32.1 ± 12.1 y (mean±s.d.); body mass 81.15 ± 12.85 kg; height 179.5 ± 6.5 cm; body fat 20.6 ± 7.6%). Interventions: Body density (BD), total body water (TBW) and bone mineral mass (BMM) were measured by hydrodensitometry, deuterium dilution and dual energy X-ray absorptiometry (DXA), respectively. These measures were used to determine two (hydrodensitometry: BD; hydrometry: TBW)-, three (BD and TBW)- and four- compartment (BD, TBW and BMM) FFM values. DXA also provided three compartment derived FFM values. RMR was measured using open circuit indirect calorimetry. Results: Three (body fat group: lean, moderate, high) x five (body composition determination: hydrodensitometry, hydrometry, three-compartment, DXA, four-compartment) ANOVAs were conducted on FFM and RMR kJ.kg FFM-1.d-1. Within-group comparisons revealed that hydrodensitometry and DXA were associated with significant (P < 0.001) over-estimations and underestimations of FFM and RMR kJ.kg FFM-1.d-1, respectively, compared with four-compartment-derived criterion values. A significant interaction (P < 0.001) resulted from DXA's greater deviations from criterion values in lean subjects. While hydrometric means were not significantly (P ≥ 0.68) different from criterion values intraindividual differences were large (FFM: -1.5 to 2.9 kg; RMR: -6.0 to 3.2 kJ.kg FFM-1.d-1). Conclusion: The relationship between RMR kJ.kg FFM-1.d-1 and exercise status would best be investigated using three (BD, TBW)- or four (BD, TBW, BMM)-compartment body composition models to determine FFM. Other models either significantly underestimate indexed RMR (hydrodensitometry, DXA) or display large intraindividual differences (hydrometry) compared with four-compartment derived criterion values.
- Multicompartment body composition models
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Nutrition and Dietetics