Changes in body fat: measurements by neutron activation, densitometry and dual energy X-ray absorptiometry

The measurement of body fat in ten subjects (BMI from 22 to 43 kg/m2), and in particular the changes arising from a ketogenic diet, by the techniques of in vivo neutron activation analysis (NAA), densitometry (using two- and four-compartment models) by under water weighing (UWW) and dual energy X-ray absorptiometry (DXA) was compared. The association between techniques for the fat changes was generally high (r = 0.70 to 0.98) abd significant (p < 0.05). Assessment of agreement between DXA and the other techniques revealed discrepancies with significant slope and high association (r = −0.81 and −0.64). Whilst NAA and UWW appeared to measure similar changes, DXA underestimated small changes.