weighing (Figure 4.1), potassium-40 (40K) counting, or more recently by imaging techniques such as dual-energy X-ray absorptiometry (DEXA) (which was itself calibrated against underwater weighing), computerized tomography (CT) scan and magnetic resonance imaging (MRI) (Figure 4.2). All these methods make assumptions about composition of 'average' tissues, e.g. density of fat, constant 40K of
muscles, or attenuation to X-rays from fat and lean tissues, and thus all the methods have inherent error. Overhydration and dehydration also affect the estimation of body composition. In attempts to overcome these problems, three- and four-compartment models to predict body composition have been developed, which employ separate measurements of body fat, muscle mass, body water and bones. These multi-compartment methods may improve accuracy of measurement but patients are subjected to many tests. Time and costs will limit the number of subjects that can be studied, and accumulated errors from these methods also make this model unattractive. A recently invented technique based on air displacement (BOD POD; Life Measurements Instruments, Concord, CA) has been introduced. This method measures rapidly and is less intimidating; thus it is useful for measuring body composition of children and the elderly.
It is important to recognize that there is in fact no true gold standard or reference method for body composition analysis. Thus scanning methods de pend on the resolution of imaging, and they also fail to detect fat within organs such as liver, muscles and bones. Cadaver dissection, coupled with chemical analysis, should theoretically overcome this problem, but there is a very real practical limitation through the time required for dissection and alteration in tissue hydration.
Was this article helpful?
Losing All that Excess Belly Fat and Getting a Well Toned Flat Stomach. Trimming down and toning up your entire body, from head to toe, is definitely something that many people want to do. But chances are, theres one place in particular where all that excess fat just doesnt want to seem to go away, no matter how hard you try.