Body composition

The parameters of interest in body composition analysis (bioelectric impedance analysis, BIA) are total body water (TBW), extracellular/intracellular fluid balance, fat-free mass (lean body mass or muscle mass), and fat mass. Application areas are as diversified as sports medicine, nutritional assessment, and fluid balance in renal dialysis and transplantation. 

One of the first to introduce the method was Thomasset (1965), using a two-electrode method and 1 kHz signal frequency. With just two electrodes, it is important to use large-area band electrodes to reduce the contribution from the current constrictional zones near the electrodes. With a tetrapolar electrode system, it is easier to select the preferred 

Calibration is also a major concern in BIA. Calibration can be done with more accurate but cumbersome methods such as using deuterium, underwater weighing or dual energy X-ray absorption. However, dilution methods have their own errors ( 2 L for TBW) and yield different results (e.g., 4% difference between the deuterium-TBW method and the 

0-TBW method). Although body impedance reflects tissue hydration, soft-tissue mass (lean and fat) can also be empirically derived by correlation in healthy subjects because the compartments of soft tissue are correlated with each other through physiological constants. However, physiological constants become flawed in patients with fluid disorders, which accounts for some of the conflicting results in the literature (Kyle et al., 2004). 

Body position is important because of gravitational influences on the distribution both of blood and the fluids in the stomach/intestine tissue. Direct body segment to body-segment skin contact must be avoided to have stable readings. The feet should therefore be kept at a distance from each other, and the arms should be held out from the chest. Scharfetter et al. (1998) also analyzed the artifacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy, and proposed a model for simulating the influence of stray capacitance on the measured data. 

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In order to define the obese state ia a clinical setting, it is necessary to have a means of estimating the amount of adipose (fat) tissue relative to lean body mass. Whereas highly accurate determiaations of body composition require complex laboratory procedures, large clinical studies typically employ measures of skia-fold thickness (11) or more commonly, body mass iadex (BMl) as a quantitative measure of obesity. 

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Routine monitoring of fasting lipid profile, bone mineral density, and body composition in children is not typically required during GH replacement but should be done before and after discontinuation of therapy.35... 

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Assessing the outcome of EN includes monitoring objective measures of body composition, protein and energy balance, and subjective outcome for physiologic muscle function and wound healing. 

The volume of distribution of many drugs is significantly increased or decreased in patients with CKD. Changes result from altered protein or tissue binding, or pathophysiologic alterations in body composition (e.g., fractional contribution of total body water to total body weight). 

Body composition 1 Total body water 1 Lean body mass T Body fat or i Serum albumin <-> or T -Acid glycoprotein (T by several disease states)... 

Ke HZ, Paralkar VM, Grasser WA, Crawford DT, Qi H, Simmons H, et al. (1998) Effects of CP-336,156, a new, nonsteroidal estrogen agonist/antagonist, on bone, serum cholesterol, uterus, and body composition in rat models. Endocrinology 139 2068-2076... 

Speed, M. A., Wang, D. I. C., and King, J. (1996). Specific aggregation of partially folded polypeptide chains The molecular basis of inclusion body composition. Nat. Biotechnol. 14, 1283-1287. 

Binder EF, Yarasheski KE, Steger-May K et al. (2005) Effects of progressive resistance training on body composition in frail older adults results of a randomized, controlled trial. J Gerontol A Biol Sci Med Sci 60(11) 1425-1431... 

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