CLEARING UP THE CONFUSION
It is difficult to distinguish by looking at a scale what technology is used to calculate body fat and composition readings. Many competitors have taken advantage of this and imply that BIA technology is used in their body fat monitors.
By using Body Mass Index based calculation readings, products may be cheaper but are far less accurate. Here are the reasons why:
* BMI is a generic mathematical calculation derived from height and body weight.
* BMI equations do not directly measure body fat, body water etc, but it can be assumed that the higher the BMI the higher the body fat.
* Growing research clearly shows that BMI is inaccurate in 25% – 30% of cases as it does not differentiate between muscle and fat.
* This inaccuracy increases when a user has an athletic build or is a child.
* Any body fat monitor with 2 footplates on the scale platform uses BMI based calculations for body fat readings. The BMI readings used for generic body fat readings cannot calculate muscle mass, abdominal fat etc.
2 FOOTPLATE MONITORS = BMI EQUATIONS USED TO CALCULATE READINGS NOT BIA TECHNOLOGY
HOW DOES TANITA BIA COMPARE
How Tanita BIA compares to other techniques used in body composition analysis
There are other methods of estimating body fat available. The following is a summary of the most common ones.
DEXA (Dual Energy X-ray Absorptiometry)
This method is generally considered the gold standard because of its reliability, precision and the fact that is based on three body components (fat, muscle and bone) as opposed to just two (fat and muscle) as in most other methods, including hydrostatic weighing. It allows fat distribution throughout the entire body to be read in a single scan. The equipment used is very expensive and requires the subject to lie perfectly still for 10 - 20 minutes while the scan is taken. DEXA is found mainly in research facilities.
Hydrostatic Weighing or Densiometry ("Dunk Tank")
Done correctly, this method is also accurate and often gives repeatable results. It too is considered a gold standard in body composition analysis. However, the test is somewhat subjective because it relies on the subject's ability to expel all oxygen from their lungs while submerged in a tank of water. Oxygen remaining in the lungs will skew the results. As well as being considerably inconvenient to the subject, the 'tank' is also expensive, depending on the type of equipment used and the underwater facility. In clinical settings, this procedure is repeated a number of times and an average is taken. Because of the expense, lengthy testing process and physical burden to the subject, this method is more suitable for research studies.
Biolectrical Impedance Analysis uses a safe electrical signal to measure body impedance. The signal is conducted through the water contained in the body. Lean tissue has more water than fat tissue and allows the signal to pass easily. The fat tissue resists the signal, which is termed impedance.
Conventional Bioelectrical Impedance Analysis methods are accurate, though not as convenient as the Tanita BIA method and may be somewhat subjective, as they rely on the consistent, precise placement of electrodes on the body. A 1cm electrode variation on any limb dramatically changes the reading, so trending results may not be accurate. The user lies down while electrodes are placed on a wrist and opposite ankle. Although this procedure can be performed in a doctor's surgery or clinic, it is not as convenient or as objective as the Tanita BIA method.
Tanita's BIA method produces accurate results that are highly correlated with both DEXA (Tanita's reference method) and Hydrostatic Weighing (within +/- 4 percentage points.) It produces objective test results that are highly repeatable (less than 1% variation within itself) when used under consistent conditions. Hydrostatic Weighing can have up to 4% variation. The equipment is not expensive, making Tanita a professionally accepted method that can be adapted easily for home use. There is no physical imposition to the user; no need for a trained technician to operate the equipment; and the entire procedure takes less than one minute.
This is a highly subjective method of measuring body fat and relies on a trained and certified technician testing multiple sites on the body. Although the equipment is inexpensive and portable, this test depends on the skills of the attending technician and the quality of device used; therefore, the method may not be suitable for trending applications or obtaining repeatable results. The use of callipers is invasive to many people, leaving them uncomfortable with the necessary multiple-site skinfold pinches. In addition, the more obese the subject, the more difficult it becomes to "pinch" the skin correctly. Despite the contention that subcutaneous fat makes up about half of the total body fat there is no data to support this statement. Furthermore, because there is little information on the distribution of fat in the body of the population at large, the validity of using skinfold equations to predict body composition is restricted to populations from whom these equations were derived.
Body Mass Index (BMI)
BMI is probably the most widely known method of determining whether a person is the correct weight for their height. BMI involves a simple calculation - a person's weight in kg is divided by their height in m². Although a simple and inexpensive method to use, it does not distinguish between lean body mass and fat mass and only has a modest correlation with actual body fat levels. The BMI calculation does not take different body types into account and can result in misclassifications (such as in the case of professional athletes and bodybuilders.)
NIR (Near Infra-Red)
A fibre optic probe measures tissue composition at various sites on the body. This method has become popular because it is simple, fast and non-invasive and the equipment is relatively inexpensive. However, studies have produced mixed results and a high degree of error has occurred with very lean and very obese people. Numerous sources report that more research is needed to substantiate this method.
It is important to remember, however, that none of these methods measure body fat directly. That can only be achieved during an autopsy.