Science and CSU

The body seen via DXA




The relatively new DXA scan, short for dual energy x-ray absortiometry, offers the advantage of showing body fat, muscle mass and bone in the same image.

A 2006 study co-authored by Cal Poly San Luis Obispo researcher Susan Puhl compared DXA scan results with those obtained from four other commonly used methods to gauge body fat, including skinfold measurements and bioelectric impedance analysis. (Puhl, a kinesiology professor at Cal Poly, died in 2007.)

(Science & the CSU takes “A Closer Look” at obesity work here.)

The scans shown here—conducted by one of Puhl’s co-authors, Dr. Mary Oates of Santa Maria—show the “before” (above, left) and “after” (lower, right) body composition of a contestant on the NBC program “The Biggest Loser.” (Click on them to enlarge them.)

The study by Puhl, Oates and W.K. Wacker of GE Healthcare—titled “Total Body %Fat – Comparison of DXA With Other Body Composition Methods”—concluded:

“Prodigy reported generally higher estimates of percent fat than the other body composition techniques, with somewhat larger differences in females than in males….

“Clinically, it is inappropriate to compare percent body fat across methods. They are not interchangeable. Information clearly shows that BMI is not an appropriate substitute for percent body fat. In addition, we do not want to overlook the obvious benefit that DXA provides additional information about lean mass and bone mass, which other methods do not.”

Used with permission, the images above come from this report by Oates: “The Use of DXA for Total Body Composition Analysis – Part I”

— Sean Kearns

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