Comparison of dual-energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance analysis for the assessment of body composition in morbidly obese women

Background/Objectives: We evaluated the agreement of air displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) with dual-energy X-ray absorptiometry (DXA) for the assessment of percent fat mass (%FM) in morbidly obese women. Subjects/Methods: Fifty-seven women aged 19-55 years and with a body mass index (BMI) ranging from 37.3 to 55.2 kg/m ² were studied. Values of %FM were obtained directly from ADP and DXA, whereas for BIA we estimated fat-free mass (FFM) from an equation for morbidly obese subjects and calculated %FM as (weight-FFM)/weight. Results: The mean (s.d.) difference between ADP and DXA for the assessment of %FM was -2.4% (3.3%) with limits of agreement (LOA) from -8.8% to 4.1%. The mean (s.d.) difference between BIA and DXA for the assessment of %FM was 1.7% (3.3%) with LOA from -4.9% to 8.2%. Conclusion: ADP-DXA and BIA-DXA are not interchangeable methods for the assessment of body composition in morbidly obese women.