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United States Department of Agriculture

Agricultural Research Service

Title: Measuring Body Fat in Children and Young Adults: Comparision of Bioelectrical Impedance Analysis, Total Body Electrical Conductivity, and Dual-Energy X-Ray Absorptiometry

item Ellis, Kenneth - BAYLOR COLL OF MEDICINE

Submitted to: International Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 1966
Publication Date: N/A

Interpretive Summary: Obesity is an increasing health problem among U.S. children. Accurate assessments of body fat are essential in order to develop useful dietary treatments. We measured body fat and lean mass in 99 people age 5-22 years old. Our purpose was to compare various methods of fat measurement to find out if they agreed (came up with similar results), since these are all widely used methods in scientific studies. We used two kings of bioelectrical impedance analysis, body electrical conductivity and dual energy x-ray absorptiometry. We found big differences among methods. Only four subjects were identified as obese by all four methods, and the overweight classification varied most of all. This study is valuable to medical science. It shows the difficulty of trying to compare findings among obesity studies that use different methods, and the importance of using (and developing) the most accurate method to determine a subject's fat classification before trying to figure out the effectiveness of a particular dietary treatment. Accuracy suffers if the same person could be classified as "normal" or "overweight" using different yardsticks.

Technical Abstract: Objective: To determine the level of agreement for body fatness measurements among four body composition techniques. Subjects: 99 healthy children and young adults ( 63 males, 36 females; ages: 5-22 y) Measurement: Bioelectrical impedance analysis (BIA), bioelectrical impedance spectroscopy (BIS), total body electrical conductivity (TOBEC), and dual-energy x-ray absorptiometry (DXA) measurements of fat-free mass (FFM), body fat, and %Fat. Results: Estimates for body fat and FFM were highly intercorrelated ( r > 0.95, p < 0.0001) among the four methods. Comparison of the absolute estimates for body fat and FFM, however, revealed significant differences between methods; mean differences ranging up to 4.2 +/- 2.7 kg. Classification rates into normal, overweight, and obese groups on the basis sof %Fat were significantly method dependent. Conclusions: The lack of interchangeability for fatness classification make it difficult to ensure that similar groups of subjects can be selected for the same %Fat characteristics when different methods. Furthermore, this limitation restricts comparison of findings among different studies when the subjects were not classified using the same measurements.

Last Modified: 4/21/2015
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