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Body composition study in the elderly: comparison between tritium dilution method and dual photon absorptiometry
G Sergi1, P Perini, M Bussolotto
1Department of Internal Medicine, University of Padova, Italy.
Journal of Gerontology
|November 1, 1993
Summary
The constant hydration of fat-free mass (FFM) is accurate for elderly body composition studies. Total body water (TBW) methods reliably estimate FFM in older adults, supporting existing hydration values.
Area of Science:
- Gerontology
- Human Physiology
- Body Composition Analysis
Background:
- Elderly body composition studies often use total body water (TBW) to estimate fat-free mass (FFM), assuming constant FFM hydration (TBW/FFM = 0.732).
- Variability in FFM hydration within healthy elderly populations requires verification of this assumption.
Purpose of the Study:
- To assess the accuracy of TBW-derived FFM estimation in elderly individuals.
- To investigate the hydration variability of FFM in healthy elderly subjects.
Main Methods:
- FFM was measured in 27 healthy elderly subjects (76 ± 7 years) using dual-photon absorptiometry (DPA) and TBW (3H2O).
- Resting metabolic rate (RMR) was measured via indirect calorimetry to validate FFM estimation accuracy.
Main Results:
- FFM hydration ranged from 63.6-80.4% (mean 71.9 ± 4.9%), wider than adult ranges but not significantly different from the 0.732 constant.
- TBW-derived FFM values were comparable to DPA-measured FFM.
- Strong correlations were observed between RMR and both FFM-DPA (r = .89) and FFM-TBW (r = .85).
Conclusions:
- Both DPA and TBW methods accurately estimate FFM in the elderly.
- The standard FFM hydration value of 0.732 is applicable for body composition studies in older adults.