Bioelectrical impedance analysis in clinical practice: a new perspective on its use beyond body composition equations. Curr Opin Clin Nutr Metab Care. 2005;8:311–317.
Methodological limitations of BIA may affect the ability of the method to accurately determine body composition. The primary issues with BIA are: One such limitation is the placement of the sensors, and their ability to give readings of total body composition.
Summary of bio-impedance technique ▪ Based on the principle that body fat impedes electric current more than body protein ▪ Impedance is a drop in voltage when a small constant current with a fixed frequency passes between electrodes spanning the body
▪ Impedance is a drop in voltage when a small constant current with a fixed frequency passes between electrodes spanning the body ▪ Predictive equations estimate TBW, FFM and body cell mass (BCM) using sex, age, weight, height and race
Potential errors in the application of mixture theory to the analysis of multiple-frequency bioelectrical impedance data for the determination of body fluid volumes are assessed. Potential sources of error include: conductive length; tissue fluid resistivity; body density; weight and technical errors of measurement.
While the theory behind BIA sounds nice, it is problematic. First, an electrical current will follow the path of least resistance through your body. This means that, if you carry a large amount of fat underneath your skin, the BIA won't even hit it; the current will instead pass through internal tissues.
The human body is not uniform either in length, cross-sectional area, or ionic composition and this affects the accuracy of BIA measurements [15]. In addition, body impedance varies among different ethnic groups and influences the accuracy of BIA [21].
It's important to bear in mind that no method of body composition measurement is completely accurate. The margin of error for BIA is roughly four percent, which can be compared to the skinfold caliper method.
The accuracy of BIA measurements is limited by different sources of error such as physical model, cross sectional area, ethnicity, body hydration, age and level of body fat among other variables. Equation for each population is required as they can produce overestimation when manufacturer's equations are used.
Bioelectrical impedance analysis (BIA) is a method for measuring body composition based on the rate at which an electrical current travels through the body. Body fat (adipose tissue) causes greater resistance (impedance) than fat-free mass and slows the rate at which the current travels.
BIA can estimate your body fat within a margin of error of about 3-4%. Bioelectrical impedance analysis calculates percent body fat by measuring resistance to a low level of electrical current.
advantages: this method of body composition analysis is very simple and quick to perform, and if you have the right equipment can be done at home. disadvantages: The equipment is relatively expensive (units on the low end of the scale are available for about $100), with prices ranging up to thousands of dollars.
BIA is considered reasonably accurate for measuring groups, of limited accuracy for tracking body composition in an individual over a period of time, but is not considered sufficiently precise for recording of single measurements of individuals.
The accuracy of BIA measurements is limited by different sources of error such as physical model, cross sectional area, ethnicity, body hydration, age and level of body fat among other variables. Equation for each population is required as they can produce overestimation when manufacturer's equations are used.
Therefore, acute alterations in hydration do indeed lead to changes in body mass resulting in changes in BIA-derived body fat percentage [22,24,27]. A study performed in morbidly obese patients also revealed overestimation of body fat using BIA method due to increased extracellular water [13].
Accuracy: Accuracy varies, with an error rate that ranges from 3.8–5% body fat but may be higher or lower depending on the device used (3, 13 ). Instructional videos: Here are examples of inexpensive BIA devices with hand electrodes, foot electrodes and hand and foot electrodes.
Bioelectrical impedance analysis (BIA) is a noninvasive method based on the electrical current conductance properties of tissues. It has been used to detect perioperative fluid accumulation and appears to be better than daily fluid balances at detecting changes in body weight.48,49 Thoracic BIA has proved useful for early identification of an increase in lung water in patients at risk for pulmonary edema 50,51 and may detect pulmonary fluid not apparent on a chest radiograph. 52 However, the clinical application of BIA in intensive care medicine is still limited, and its place remains to be established.
Thus, early detection and monitoring of body cell mass is critical, because it is the compartment of body tissue that is most representative of functional status. This compartment accounts for intracellular water, red blood cells, and organ and skeletal tissue, and is the site of all metabolic activity [ 39 ].
Bioelectrical impedance analysis (BIA) is a technique that applies an electrical current through the body to estimate muscle mass based on the current’s conduction through water , since muscle has the greatest water composition of all body tissues [188,189].
Bioelectrical impedance analysis (BIA) is a technique that has proven to be safe, generally acceptable to patients, and easy to use [109,110] . BIA is used for determining fluid management and increasingly for evaluating protein-energy status.