Body Fat Measurement by Air Displacement Plethysmography: Theory, Practice, Procedures, and Applications
The importance of measuring body composition has increased because of the need to evaluate changes in nutritional status that can affect body reserves differentially. These changes can be detected only by using valid body composition measurement techniques. Air displacement plethysmography (ADP) has proved to be a valid method for determining body composition in adults and children. ADP measures body volume using a subtraction technique in which body volume equals reduction in the volume of a chamber resulting from the introduction of the individual into the chamber. There are two versions of the plethysmograph, one for adults and children, the BOD POD, and another version for infants, the PEA POD. Both versions correct the raw body volume measurement for the isothermal effect of skin on air and thoracic gas volume. The body volume is then converted to mass and density relationships for body fat and fat-free masses, and body fat percentage is calculated. In both formats, ADP has good reliability in terms of body volume and fat percentage and has been validated against three-compartment (3C) and four-compartment (4C) models. It has also been used to develop body composition prediction equations for methods like bioimpedance analysis (BIA) and anthropometry in a wide range of populations. Among other applications, ADP has been applied successfully to determine the relationship between body size and adiposity, to evaluate intervention programs based on diet or physical activity, and in athletes, to evaluate body composition changes related to training in different sports.
KeywordsBody Composition Anorexia Nervosa Isotope Ratio Mass Spectrometry Body Volume Central Process Unit
- 2C, 3C, 4C
Two-, three-, and four-compartment models
- % fat
Percentage of fat mass
Air displacement plethysmography
Body mass index
Coefficient of variation
Dual X-ray absorptiometry
Hydrostatic weighing, hydrodensitometry
Surface area artifact
Standard error of the estimate
We thank the Centro de Investigacion en Alimentacion y Desarrollo (CIAD, A.C.) (Research Center for Food and Development) in Hermosillo, Mexico, for providing the equipment and facilities for the illustration of the BOD POD human measurement procedure. We specially thank Erika Ibarra and Alma Robles, for their assistance and participation in the photographic procedures, and Aida Espinosa for her assistance with drawings and graphics. We thank Cruz Teros, official photographer of the University of Sonora for taking the pictures of the BOD POD measurement procedure. We also thank Manuel Ramirez and Karen Schlosser from the Instituto de Nutricion de Centro America y Panama (Institute of Nutrition of Central America and Panama, INCAP) in Guatemala City, Guatemala, for providing the photographs of the hydrostatic weight measurement. Thanks also to Life Measurement Inc. (LMI), California, USA, for allowing us to use their images.
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