Body Composition Using Air Displacement Plethysmography In Obese Adults: Effect Of Estimated Versus Measured Thoracic Gas Volume

The Bod Pod uses air displacement plethysmography (ADP) to measure body volume, and, with the measurement of body mass, is able to calculate body density for the analysis of body composition. However, total body density will be incorrectly estimated if the gas volume within the lungs at the time of the body volume measurement, termed thoracic gas volume (VTG), is measured inaccurately. The Bod Pod can account for VTG by using a prediction equation based on age and height (VTGpred), or by direct plethysmographic measurement (VTGmeas). It is well established that obesity (OB) alters operational lung volumes at rest, which has the potential to increase the error associated with VTGpred and the corresponding estimation of body composition. The purpose of this study was to examine the effect of VTGpred and VTGmeas on estimates of body fat percentage (�) using the Bod Pod (�VTGpred, and �VTGmeas, respectively) as compared to � from dual X-ray absorptiometry (DXA) and a subcomponent estimation from DXA, trunk fat percentage, in normal weight (NW) and (OB) adults.