I have found more extensive information on impedance testing, which
reveals
that my initial suggestion of using an ohmmeter/chart combination is
not
practical.  Full details can be found at:-

        http://text.nlm.nih.gov/nih/ta/www/15.html

This study notes that

"Impedance measurements are linked with output variables such as body
fat
through statistical association rather than on the basis of
biophysical
principles."

and therefore great care is required in the interpretation of the
results.

Andy.