Abstract
BackgroundDual energy x-ray absorptiometry (DXA) is widely used for body composition measurements in normal-weight and overweight/obese individuals. The limitations of bone densitometers have been frequently addressed. However, the possible errors in assessing body composition in overweight individuals due to incorrect positioning or limitations of DXA to accurately assess both bone mineral density and body composition in obese individuals have not received much attention and are the focus of this report.DiscussionWe discuss proper ways of measuring overweight individuals and point to some studies where that might not have been the case. It appears that currently, the most prudent approach to assess body composition of large individuals who cannot fit under the scanning area would be to estimate regional fat, namely the regions of thigh and/or abdomen. Additionally, using two-half body scans, although time consuming, may provide a relatively accurate measurement of total body fat, however, more studies using this technique are needed to validate it.SummaryResearchers using bone densitometers for body composition measurements need to have an understanding of its limitations in overweight individuals and address them appropriately when interpreting their results. Studies on accuracy and precision in measurements of both bone and soft tissue composition in overweight individuals using available densitometers are needed.
Highlights
Dual energy x-ray absorptiometry (DXA) is widely used for body composition measurements in normal-weight and overweight/obese individuals
Summary: Researchers using bone densitometers for body composition measurements need to have an understanding of its limitations in overweight individuals and address them appropriately when interpreting their results
Current bone densitometers are limited to a scanning area that cannot accommodate some overweight/obese individuals
Summary
Use of bone densitometers in weight loss studies In weight loss studies where DXA is used to evaluate lean and fat tissue, overweight/obese individuals range widely in body weight and size [8,13,14,15,16,17,18,19,20]. Half-body DXA scans for the assessment of soft tissue Tataranni and Ravussin [28] suggest measuring soft tissue of obese individuals by scanning only one side of the body They found total body composition results from right and left sides only differed minimally in both overweight and normal-weight individuals. The authors found weight change leads to considerable anomalies in measuring changes in bone mineral in all three brands of DXA machines (Hologic, Lunar and Norland), with the most serious ones occurring with Hologic [29] These inaccuracies were suspected to be due to the use of different software modes (enhanced vs standard) and the different assumptions manufactures make regarding fat http://www.biomedcentral.com/1471-2342/5/1 distribution [29]. Phantom measurements revealed that both fan beam instruments were subject to minor magnification effects, and measurements of BMD and BMC were both dependent on the height of a bone [30]
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