Research

Validity of air-displacement plethysmography in the assessment of body composition changes in a 16-month weight loss program

Cláudia S Minderico¹ , Analiza M Silva¹ , Pedro J Teixeira¹ , Luis B Sardinha¹ , Holly R Hull² and David A Fields^3,4

¹Exercise and Health Laboratory, Faculty of Human Movement, Health and Exercise Science, Technical University of Lisbon, Portugal

²University of Oklahoma, Norman, OK, USA

³Department of Pediatrics, Children's Medical Research Institute's Metabolic Research Center, University of Oklahoma Health Science Center, OK, USA

⁴Assistant Professor, University of Oklahoma Health Science Center, School of Medicine Department of Pediatrics, OUCP Diabetes & Endocrinology, 940 NE 13^th Street, CH 2B2426, OKC, OK 73104, USA

author email corresponding author email

Nutrition & Metabolism 2006, 3:32doi:10.1186/1743-7075-3-32

Published:	22 August 2006

Abstract

Objective

To compare the accuracy of air displacement plethysmography (ADP) and dual energy x-ray absorptionmetry (DXA) in tracking changes in body composition after a 16 month weight loss intervention in overweight and obese females.

Methods

93 healthy female subjects (38.9 ± 5.7 yr, 159.8 ± 5.6 cm, 76.7 ± 9.9 kg, 30.0 ± 3.4 kg/m²) completed a 16 month weight loss intervention. Eligible subjects attended 15 treatment sessions occurring over the course of 4 months with educational content including topics relating to physical activity and exercise, diet and eating behavior, and behavior modification. In the remaining 12 months, subjects underwent a lifestyle program designed to increase physical activity and improve eating habits. Before and after the intervention, subjects had their percent body fat (%fat), fat mass (FM), and fat-free mass (FFM)) assessed by DXA and ADP.

Results

Significant differences (p ≤ 0.001) were found between DXA and ADP at baseline %fat (46.0 % fat vs. 42.0 % fat), FM (35.3 kg vs. 32.5 kg) and FFM (40.8 kg vs. 44.2 kg) as well as at post intervention for %fat (42.1% fat vs. 38.3 % fat), FM (30.9 kg vs. 28.4 kg) and FFM (41.7 kg vs. 44.7 kg). At each time point, ADP %fat and total FM was significantly lower (p ≤ 0.001) than DXA while FFM was significantly higher (p ≤ 0.001). However, both techniques tracked %fat changes similarly considering that there were no differences between the two means. Furthermore, a Bland-Altman analysis was performed and no significant bias was observed, thus demonstrating the ability of ADP to measure body fat across a wide range of fatness.

Conclusion

At baseline and post weight loss, a significant difference was found between ADP and DXA. However, the results indicate both methods are highly related and track changes in %fat similarly after a weight loss program in overweight and obese females. Additionally, the mean changes in %fat were similar between the two techniques, suggesting that ADP can be translated to its use in clinical practice and research studies as DXA currently is used.