Most individuals embarking upon a weight-loss program set a goal to lose a certain number of pounds. They often become obsessed with checking their progress on the bathroom scale. Although a change in body weight is of importance, it is really very incomplete data. The issue is that the scale does not tell you what type of body tissue you are losing or gaining. It is very common for people to think they are achieving a desirable result in losing weight when in fact they are losing lean, healthy tissue and not fat. It is also very possible to see no change on the bathroom scale as your body is simultaneously building lean, healthy tissue and burning fat. 

The numbers people should be concerned with are those concerning their body composition rather than body weight. There are a number of methods available to measure body composition including dual energy x-ray absorptiometry (DEXA), radioisotope dilution, and computerized tomography scanning. These methods are not readily available, however. The more commonly used techniques include hydrostatic (underwater) weighing, skinfold testing, near-infrared interactance, bioelectrical impedance, girth or circumference measurements, and body mass index (weight divided by height squared). Of these methods, under-water weighing was long considered the gold standard. In the last couple of years, a company called RJL Systems has developed advanced computer software, based on DEXA, for use with their bioelectrical impedance analyzer. This system is more accurate and reproducible than underwater weighing. What’s more, it gives additional extremely valuable information not available with the other techniques. 

Bioelectrical impedance analysis works in the following way. The subject lies down on a flat surface and has electrodes attached to the wrist and ankle of their dominant side. A device is attached to the electrodes, which sends a very weak electrical current through the body (nothing is felt). The device measures the voltage drop of this current and yields two measurements: resistance and reactance. The values for resistance and reactance are entered into a computer program along with the subject’s height and weight. Mathematical analysis of these data yields the body composition measurements. 

Electrical resistance is a measure of ability to conduct an electrical current. A good conductor has low resistance. The extracellular water (ECW) or fluid found outside the body cells, in combination with electrolytes, is the main conductor of the body. Fat, which has a low water content, has a high resistance. The resistance value is used to give a measure of the extracellular volume of the body. 

Electrical reactance is an indication of capacitance - the ability of the body cells to store an electrical charge. Reactance is directly proportional to intracellular volume. 

All other commonly available methods of measuring body composition divide tissue into two compartments: fat and fat-free mass (FFM). This is valuable information. However, the RJL Fluid and Nutrition Analysis takes things one step further. Not only does it measure fat and fat-free mass, but it further sub-divides fat-free mass into the compartments of body cell mass (BCM) and extracellular tissue (ECT). Measures of total body water (TBW), extracellular water (ECW), intracellular water (ICW), and phase angle are also made. Also, an estimate of basal metabolic rate is given. Now, let’s see what all this means and how it is of value to people trying to lose weight, bodybuilders, endurance athletes, individuals on detoxification or anti-aging programs, and the acutely and chronically ill. 

Body cell mass (BCM) is one of the most important values obtained with this testing. BCM is the measure (given in pounds and as a percentage of body weight) of all the living metabolically active tissue in the body - muscle, organ, and blood cells. Contained within BCM are all the body’s intracellular water (ICW), and proteins and other solids. With serial testing, a change in body cell mass is due primarily to a change in muscle mass. Changes in BCM can be picked up within 72 hours. Increases in BCM equate with anabolism - the process of converting food into living tissue. Decreases in BCM are involved in catabolic (breaking down) processes. BCM is the tissue that is consumed (with negative consequences) in illness, disease, aging, under-nutrition, and athletic overtraining. Decreasing BCM from any cause leads to weakened immunity, failure to thrive, and eventually death. 

In the early stages of catabolism, there is no change in fat-free mass (FFM) as healthy cells break down and BCM becomes extracellular tissue (ECT). The other methods of body composition analysis that measure only FFM are insensitive to these changes. The RJL system, by dividing FFM into BCM and ECT, can detect catabolism in the earliest stages and allow for early intervention and a more successful outcome. Decreases in BCM have been measured in asymptomatic HIV patients when other methods of analysis yielded normal values. Maintaining BCM can prolong survival in AIDS patients. 

Another important application of BCM measurement is in weight loss programs. It is critical to track BCM during weight loss so that lifestyle changes can be made, if necessary, before damage is done. With improper weight loss programs, BCM decreases and the body’s set point (resting energy requirements) is reduced. The body will then store fat more easily. BCM measurements are also invaluable to the bodybuilder. Increasing BCM means muscle is being built, decreasing BCM means muscle is being broken down, regardless of what the bathroom scale implies. A normal value for BCM may range from 30% to 55% of body weight. 

Intracellular water (ICW) is the potassium based fluid volume located in the BCM. Extracellular water (ECW) is the sodium based fluid volume located in the extracellular tissue (ECT). ECT is also made up of proteins and other solids and includes such tissues as the tendons, skin, bones, and other connective tissues. ECW is located between the cells, within blood vessels, and other spaces such as the intestines. ECW and ICW are measured in liters and expressed as percentages of total body water. Normal values for ICW range from 41% to 70%. Normal values for ECW range from 29% to 61%. 

Changes in ICW mirror changes in BCM, and changes in ECW reflect changes in ECT. The balance between ICW and ECW indicate whether the body is in an anabolic or catabolic state. Sarcopenia, the loss of lean body mass that occurs with aging, can be seen in decreasing ICW and increasing ECW values. 

Hydration is critical to the metabolic performance of the muscle cell. According to Haussinger, et al, from the May 22, 1993 issue of The Lancet, "An increase in cellular hydration (swelling) acts as an anabolic proliferative signal, whereas cell shrinkage is catabolic and anti-proliferative. Cellular hydration state is mainly determined by the activity of ion and substrate transport systems in the plasma membrane." Hormones, anabolic steroids, cytokines, free radicals, chemotherapeutic and other drugs, amino acids and creatine monohydrate are among the compounds that influence ICW. 

TBW, ECW, and ICW can reveal dehydration, water retention, and effectiveness of treatment in correcting these conditions. Fluid changes usually occur first in the ECW. For example, in dehydration the ICW only begins to decrease after there has been significant depletion of ECW. Importantly, the RJL system can be used to measure hydration status in endurance athletes, as a small loss of body water can adversely affect performance. 

Another valuable bit of data produced by this system is the phase angle, which is a mathematical relationship between resistance and reactance. The phase angle is an indication of the health of the body cell membranes. With ill health the cell membrane fails, allowing leakage of the cell’s contents. With a decrease in the number of the body’s cells the reactance and phase angle both decrease. The higher the phase angle the greater the state of health and fitness. As health improves, so does the phase angle. The normal range for the phase angle is 4° to 12°. A study of patients with congestive heart failure found altered reactance, suggesting a change in cell membrane permeability. These values improved with treatment. Other studies have found the phase angle to very accurately predict disease progression in AIDS patients. The lower the phase angle the worse the prognosis. 

The RJL Fluid and Nutrition Analysis system is used in hospital settings to monitor patients with a wide variety of conditions. Its breadth of information, accuracy, and repeatability allow for early intervention and improved outcome with patients suffering: burns, cancer, edema-dependent hypertension, AIDS, congestive heart failure, pulmonary edema, kidney disease, blood infection, and post-surgery. 

In addition to giving important information on anabolic/catabolic states and the nature of tissue and fluid change to dieters, bodybuilders, and endurance athletes, the RJL system is extremely valuable to individuals engaged in metabolic detoxification programs. My own personal experience is a good example. I was tested with the RJL system immediately before starting and one week into a detoxification program. In that one week, I lost six pounds of body weight. Importantly, my BCM did not change; indicating that I was not in a catabolic state which can be a concern on this type of program. Three and a half pounds of my weight loss were in the form of fat. I lost a liter of body fluid, with all of it coming from the ECW compartment, none from ICW. This was probably due to the fact that the first place the body stores toxins is where they will do the least harm - in the ECW. As my body excreted toxins, there was less of a demand to retain ECW to dilute them. The week of detoxification also resulted in an increase in my phase angle, indicating improved health. 

Testing with the RJL system is fast, safe, inexpensive, and non-invasive. I recommend for people to be tested at intervals of about 4 to 6 weeks for general purposes. In cases of illness or intense dietary and activity changes, testing can be performed once per week or more often.