DEXA is the gold-standard of body composition analysis; but only when NOT using the NHANES calibration which crudely increases bodybuilder’s bodyfat by around 5-percentage points; or even more if you are really big and really lean!
I have been rallying against the NHANES DEXA calibration ever since it was released. The new calibration was based on this frankly awful study that concluded DEXA needed to change its results to better agree with grossly inferior test methods (primarily Deuterium).
Ignoring academic squabbling about ‘accuracy’, the major problem with the NHANES calibration is the results are so absurd as to make all established standards of bodyfat percentages useless, and communication near impossible. With NHANES, I have seen male bodybuilders with clearly visible abs measure close to 20%, and bodybuilders with striated glutes measure over 10%. These test results do not remotely correspond to the expectations or understanding of those bodyfat levels to any experienced professional.
So it is nice when science and the medical community catch up with what we meathead bodybuilders have been saying for years. It seems there has been growing recognition and frustration with the absurdity of the NHANES calibration; particularly in athletes. Hologic – the premier manufacturer of DEXA machines – recently returned to the classic calibration as the default setting of their machines, recognising it as having always been the true and accurate measurement. Here is a link to their explanation.
If you get a DEXA scan, always request the classic, NON-NHANES calibration. It is a basic option in the DEXA software that the clinician can easily make. If you are unfortunate to have the NHANES calibration forced upon you (as many labs will do), understand that the crude NHANES algorithm simply reduced your lean mass by 5%, and added that amount to your fat mass. You can reverse the change by dividing your lean mass by 0.95 and then subtracting the lean-mass change from your fat mass.