It measures body density
, from which fat and lean mass content are estimated, by assuming standard figures for density of these components .
Based on the SIRI-equation (2) for converting body density
into a percentage body fat (PF) these densities correspond to PF's of 5.4% and 7.5% respectively which seems very unlikely given their sample was composed of 29 women and 5 men, and not for example elite male athletes.
Computation of Body density
(BD): Body density
was calculated by the standard formulae .
This method determines body density
by measuring body volume by air displacement and body weight.
Different methods are used for the measurement of obesity ranging from simple anthropometric measurements such as BMI, WC, WHR, to skinfold thickness, and body density
. A study showed considerable variation in waist and hip circumferences and WHR.
Body fat assessed from total body density
and its estimation from skinfold thickness: measurements on 481 men and women aged from 16 to 72 years.
was estimated from subcutaneous fat thickness using an ultrasound-derived prediction equation (10).
fat mass and fat free mass calculated from body density
) are modified by age, sex, and ethnicity (2,11).
Additionally, seven skin folds (triciptal, subscapular, pectoral, axillary, abdominal, suprailiac and thigh) were measured in triplicate by a trained examiner using a Cescorf[R] scientific skinfold caliper, according to the protocol of Jackson and collaborators (1980) for individuals over 18 years, to estimate body density
. After that, body fat percentage was calculated using equations proposed by Siri (1961).
was estimated based on skinfolds (8), and the percent body fat was determined based on body density
Figure 1 Body Density
, Body Fat Percentage, and Lean Body Mass Estimates Females: Body density
= 1.0994921 - 0.0009929*X + 0.0000023*[X.sup.2] - 0.0001392*age (where X = sum of triceps, supra iliac and thigh skinfold measurements, and [X.sup.2] = square of the sums of triceps, supra iliac and thigh skinfold measurements) Males: Body density
= 1.1093800 - 0.0008267*X + 0.0000016*[X.sup.2] - 0.0002574*age (where X = sum of chest, abdominal, thigh skinfold measurements, and [X.sup.2] = square of the sums of chest, abdominal, thigh skinfold measurements) The whole-body DEXA scan was performed on non-dialysis days, midweek (Wednesday or Thursday), on all patients.
These equations estimate body density
[25-30], body fat percentage [16,18,31, 32], or body fat mass  (Table 1).