Whole-body impedance--what does it measure?

• Published in: The American journal of clinical nutrition Vol. 64; no. 3; pp. 388S - 396S
• Main Authors: Foster, KR, Lukaski, HC
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bethesda, MD Elsevier Inc 01-09-1996; American Society for Clinical Nutrition; American Society for Clinical Nutrition, Inc
• Subjects: anthropometric measurements; bioelectrical impedance; Biological and medical sciences; biophysics; Body Composition; body water; Body Water - metabolism; Cellular biology; Electric Impedance; electrical conductivity; electrical properties; electrical resistance; Electrodiagnosis. Electric activity recording; extracellular fluids; Extracellular Space - metabolism; fat free mass; Fundamental and applied biological sciences. Psychology; General aspects. Body compartment; human nutrition; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Metabolisms and neurohumoral controls; Miscellaneous. Technology; Models, Biological; Nutrition; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Congress; Human; Tissue; Electrical properties; Review; Measurement method; Body composition; Electrical impedance
• ISSN: 0002-9165; 1938-3207; 1938-3207
• DOI: 10.1093/ajcn/64.3.388S

Although the bioelectrical impedance technique is widely used in human nutrition and clinical research, an integrated summary of the biophysical and bioelectrical bases of this approach is lacking. We summarize the pertinent electrical phenomena relevant to the application of the impedance technique in vivo and discuss the relations between electrical measurements and biological conductor volumes. Key terms in the derivation of bioelectrical impedance analysis are described and the relation between the electrical properties of tissues and tissue structure is discussed. The relation between the impedance of an object and its geometry, scale, and intrinsic electrical properties is also discussed. Correlations between whole-body impedance measurements and various bioconductor volumes, such as total body water and fat-free mass, are experimentally well established; however, the reason for the success of the impedence technique is much less clear. The bioengineering basis for the technique is critically presented and considerations are proposed that might help to clarify the method and potentially improve its sensitivity.