Body Fat | Reference

How does Tanita's Body Fat Analyzers compare with other methods in terms of accuracy, repeatability, cost, patient convenience, and length of procedure?"

a) DEXA (Dual Energy X-ray Absorptiometry) This method is extremely accurate and repeatable. It is also extremely expensive ($80,000-100,000); and very inconvenient for patients and users. The patient must lay supine for approximately 20-30 minutes while every section of their body is systematically X-rayed. For practical purposes, this device is mainly used in research studies.

b) Hydrostatic Weighing - If done correctly, this method is also very accurate, and the results are often repeatable. However, the test is somewhat subjective because it relies upon the subject's ability to expire all oxygen out of their lungs while submerged in a tank of water. Some subjects have been unable to totally exhale their oxygen while submerged, thus skewing the results. Also very expensive ($25,000-$35,000 depending on type of equipment used and the underwater facility). Obviously, the burden to the patient is substantial. Generally, this process is repeated a number of times, and an average is taken. This method is more suitable for research studies due to the expense, lengthy testing procedure, and physical burden to the subject.

c) TANITA TBF-105 Very accurate (within +/- 2-3% of DEXA) and offers a totally objective method of testing. Offers consistently repeatable results (only 1% variance with the TBF Series vs. up to 4% in Hydrostatic Weighing). Priced at $5,500, this equipment is inexpensive as compared to the above methods. Because the TBF Series operates like a scale, there is literally no burden to the patient. There is no need for a trained technician to operate the equipment, and the entire process takes about one minute.

d) Other BIA methods - Results are accurate, however, they are more subjective due to the variation of electrode placement (1 cm electrode variation on any limb changes reading dramatically). For this reason, this method may not give accurate trending results. The patient must be in a supine position while electrodes and conductive jelly are placed on the wrist and opposite ankle. This method is used in some physician offices. However, due to the burden to the subject and reasons listed above, it is neither as convenient nor as objective as the newer BIA method employed in Tanita's TBF Series Body Fat Analyzer/Scale.

e) Calipers - Highly subjective testing relies on a trained and certified technician testing multiple sites. "Despite the contention that subcutaneous fat makes up about half of the total body fat, there are 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."(1) Because this type of test often depends on the attending technician, the caliper method may not be suitable for trending applications or obtaining repeatable results. The cost is minimal, ranging from $15 to $200 depending on the quality and features of the individual caliper. The use of calipers is very intrusive; many patients are uncomfortable with the necessary multiple site skinfold tests.

f) MR - Near Infra-Red - This is a relatively new method of body composition analysis that offers a low level of accuracy. "Numerous researchers have reported unacceptable prediction errors (3.7% to 6.3%)."(2) "The manufacturer's equation systematically underestimated average body fatness by as much as 2 %BF to 10%BF. . . The degree of underestimation of %BF appears to be directly related to the level of body fatness."(2) The cost of this equipment is relatively low ($1,000 - $2,500 depending on the model). The NIR method is not burdensome to the subject.

1) Lukaski, Henry, PhD Methods for the assessment of human body composition: traditional and new. American Society for Clinical Nutrition. (541) 537-556-1937

2) Heyward, Vivian, Stolarczyk, Lisa, Applied Body Composition Assessment (61) 56-65-1996


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