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Bioelectrical impedance analysis
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Bioelectrical impedance analysis
Bioelectrical impedance analysis (BIA) is a method for estimating body composition, in particular body fat and muscle mass, where a weak electric current flows through the body, and the voltage is measured in order to calculate impedance (resistance and reactance) of the body. Most body water is stored in muscle. Therefore, if a person is more muscular, there is a high chance that the person will also have more body water, which leads to lower impedance. Since the advent of the first commercially available devices in the mid-1980s the method has become popular, owing to its ease of use and portability of the equipment. It is familiar in the consumer market as a simple instrument for estimating body fat. BIA actually determines the electrical impedance, or opposition to the flow of an electric current through body tissues, which can then be used to estimate total body water (TBW), which can be used to estimate fat-free body mass and, by difference with body weight, body fat.
Many of the early research studies showed that BIA was quite variable, and it was not regarded by many as providing an accurate measure of body composition. Nevertheless, it is the 4-compartment model (4C) (DXA and MRI are acceptable alternatives) – and not BIA – that is regarded as the reference method in body composition analysis.
Although the instruments are straightforward to use, careful attention to the method of use (as described by the manufacturer) should be given. [citation needed]
Simple devices to estimate body fat, often using BIA, are available to consumers as body fat meters. These instruments are generally regarded as being less accurate than those used clinically or in nutritional and medical practice. They tend to under-read body fat percentage by approximately 5 kg (±7 kg LoA[clarification needed]) on average, despite showing a linear correlation with MRI-based measurements of 0.75 and 0.81 for females and males respectively.
Dehydration is a recognized factor affecting BIA measurements, as it causes an increase in the body's electrical resistance, so has been measured to cause a 5 kg underestimation of fat-free mass i.e. an overestimation of body fat.
Body-fat measurements are lower when measurements are taken shortly after consumption of a meal, causing a variation between highest and lowest readings of body fat percentage taken throughout the day of up to 4.2% of body fat.
Moderate exercise before BIA measurements lead to an overestimation of fat-free mass and an underestimation of body fat percentage due to reduced impedance. For example, moderate intensity exercise for 90–120 minutes before BIA measurements causes nearly a 12 kg overestimation of fat-free mass, i.e. body fat is significantly underestimated. Therefore, it is recommended not to perform BIA for several hours after moderate or high-intensity exercise.
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 accurate for recording of single measurements of individuals.
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Bioelectrical impedance analysis AI simulator
(@Bioelectrical impedance analysis_simulator)
Bioelectrical impedance analysis
Bioelectrical impedance analysis (BIA) is a method for estimating body composition, in particular body fat and muscle mass, where a weak electric current flows through the body, and the voltage is measured in order to calculate impedance (resistance and reactance) of the body. Most body water is stored in muscle. Therefore, if a person is more muscular, there is a high chance that the person will also have more body water, which leads to lower impedance. Since the advent of the first commercially available devices in the mid-1980s the method has become popular, owing to its ease of use and portability of the equipment. It is familiar in the consumer market as a simple instrument for estimating body fat. BIA actually determines the electrical impedance, or opposition to the flow of an electric current through body tissues, which can then be used to estimate total body water (TBW), which can be used to estimate fat-free body mass and, by difference with body weight, body fat.
Many of the early research studies showed that BIA was quite variable, and it was not regarded by many as providing an accurate measure of body composition. Nevertheless, it is the 4-compartment model (4C) (DXA and MRI are acceptable alternatives) – and not BIA – that is regarded as the reference method in body composition analysis.
Although the instruments are straightforward to use, careful attention to the method of use (as described by the manufacturer) should be given. [citation needed]
Simple devices to estimate body fat, often using BIA, are available to consumers as body fat meters. These instruments are generally regarded as being less accurate than those used clinically or in nutritional and medical practice. They tend to under-read body fat percentage by approximately 5 kg (±7 kg LoA[clarification needed]) on average, despite showing a linear correlation with MRI-based measurements of 0.75 and 0.81 for females and males respectively.
Dehydration is a recognized factor affecting BIA measurements, as it causes an increase in the body's electrical resistance, so has been measured to cause a 5 kg underestimation of fat-free mass i.e. an overestimation of body fat.
Body-fat measurements are lower when measurements are taken shortly after consumption of a meal, causing a variation between highest and lowest readings of body fat percentage taken throughout the day of up to 4.2% of body fat.
Moderate exercise before BIA measurements lead to an overestimation of fat-free mass and an underestimation of body fat percentage due to reduced impedance. For example, moderate intensity exercise for 90–120 minutes before BIA measurements causes nearly a 12 kg overestimation of fat-free mass, i.e. body fat is significantly underestimated. Therefore, it is recommended not to perform BIA for several hours after moderate or high-intensity exercise.
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 accurate for recording of single measurements of individuals.