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Metabolically‐active portion of fat‐free mass: a cellular body composition level modeling analysis
Author(s) -
Wang ZiMian,
Heshka Stanley,
Wang Jack,
Gallagher Dympna,
Deurenberg Paul,
Chen Zhao,
Heymsfield Steven
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1028-c
Subject(s) - body water , extracellular fluid , chemistry , fat free mass , linear regression , zoology , free water , dilution , fat mass , endocrinology , medicine , extracellular , body weight , thermodynamics , mathematics , biochemistry , statistics , biology , physics , environmental engineering , engineering
The proportion of fat‐free mass (FFM) as body cell mass (BCM) is highly related to resting energy expenditure. However, the BCM/FFM ratio may have been underestimated in previous studies as the Moore equation (BCM = 0.00833 x TBK), which is typically used to predict BCM, underestimates BCM by ~11%. The aims of the present study were to develop a theoretical BCM/FFM model at the cellular level, and to explore the influences of sex, age, and adiposity on BCM/FFM. Subjects were 112 adults who had the following measurements: total‐body water by 2 H 2 O or 3 H 2 O dilution; extracellular water by NaBr dilution; total‐body nitrogen by in vivo neutron activation analysis; and bone mineral by DXA. FFM was calculated using a multicomponent model and BCM was calculated as the difference between FFM and the sum of extracellular fluid and solids. The developed theoretical model revealed that the proportion of BCM/FFM is mainly determined by water distribution ( E/I , the ratio of extracellular to intracellular water). A significant correlation (r = 0.90, P < 0.001) was present between measured and model‐predicted BCM/FFM for all subjects pooled. Measured BCM/FFM (mean +/− SD) was 0.584 +/− 0.041 and 0.529 +/− 0.041 for adult men and women ( P < 0.001), respectively. A multiple linear regression model showed that there are independent significant associations of sex, age, and %fat with BCM/FFM. Variation in the BCM/FFM is mainly dependent on water distribution with a larger E/I associated with a smaller BCM/FFM. Supported by NIDDK PO1‐42618.