37
VIII. ABOUT RESULTS
Total Body Water, Extracellular Water, and Intracellular Water)
Total Body Water (TBW) refers to the water contained in the tissues, blood, bones, and
elsewhere. TBW in a healthy (non-obese) adult can fluctuate by roughly 5% daily, influenced by
physiological activity and consumption of food and drink
4
. Due to larger size and muscle mass,
healthy adult men have more TBW than women (on average)
5
.
For healthy (non-obese) adults, TBW constitutes ~ 60% of body weight and ~ 73% of Fat-Free
Mass
6
. However, it is important to note that this percentage is not applicable to children - typically,
children have a higher percentage of body water than adults, and TBW levels reportedly decrease
further around middle age as part of the aging process
7
. In addition, various diseases can affect
body water percentage, including renal deficiency, diabetes, cardiac failure, and cancer
8
.
Therefore, BIA estimations should be used with particular caution if subject's body water differs
significantly from the representative populations used to formulate BIA algorithms.
TBW can be divided into Intracellular Water (ICW) and Extracellular Water (ECW). ICW:ECW
proportion for healthy populations is roughly 3:2 (ECW/TBW=~0.38)
9
. The Edema Index
calculates this ratio for usage by professionals.
Soft Lean Mass
Soft Lean Mass is the weight of the body after deducting total fat mass and minerals.
(Weight - Body Fat Mass - Minerals = Soft Lean Mass)
Fat-Free Mass
Fat-Free Mass (FFM) is the weight of the body after deducting total fat mass.
(Weight - Body Fat Mass = Fat-Free Mass)
Protein
This is an estimation of the protein contained in the body.
4. Askew EW Present Knowledge in Nutrition (7th ed) 1996, p.98-107
5. Lesser GT, Markofsky J. Body water compartments with human aging using fat-free mass as the reference standard.
1979. Am J Physiol, 236, p.R215-R220.
6. Wang ZM, Deurenberg P, Wang W, Pietrobelli A, Baumgartner RN, Heymsfield SB. Hydration of fat-free body mass:
review and critique of a classic body-composition constant. The American Journal of Clinical Nutrition. 1999. Vol.69 Issue
5, p.833-841.
7. Cameron CW, Guo SS, Zeller CM, Reo NV, Siervogel RM. Total body water for white adults 18 to 64 years of age: The
Fels Longitudinal Study. 1999. Kidney Internationalk Vol.56 Issue 1, p.244-252
8. Moore FD, Haley HB, Bering EA, Brooks L, Edelman I. Further observations on total body water. Changes of body
composition in disease. 1952. Surg Gynecol Obstet, 95, p.155-180
9. Tai R, Ohashi Y, Mizuiuri S, Aikawa A, Saki K. Association between ratio of measured extracellular volume to expected
body fluid volume and renal outcomes in patients with chronic kidney disease: a retrospective single-center cohort study.
BMC Nephrology, 2014;15:189
Values
TBW
SLM
FFM
Weight
Normal Range
Compartments
Body Composition Analysis
Intracellular Water
ICW
( L )
Extracellular Water
ECW
( L )
Protein
( kg )
Mineral
( kg )
Body Fat Mass
BFM
( kg )
33.8%
22.1%
15.5%
4.7%
23.9%
16.4
10.7
7.5
2.3
11.6
27.1
34.6
36.9
48.5
17.0 ~ 20.8
10.4 ~ 12.8
7.4 ~ 9.1
1.6 ~ 2.7
8.7 ~ 13.6
