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Body Composition Explained: What is (BIA) Bioimpedance Analysis \u0026 how it helps measure your health.BIA body composition analyzer -
The criterion method for determining body composition is the four-compartment model 1] fat mass, 2] total body water, 3] bone mineral mass, and 4] residual mass , and should be used when assessing the validity of BIA measurements.
BIA has been compared to the four-compartment model in several studies using various populations. Sun et al. It is important to note that this analysis utilised DEXA as the reference method, which may also lead to further error, as eluded to earlier in this review read my article on the use of DEXA scanning for body composition assessment HERE.
The validity of BIA for one-off measures of body composition Despite studies showing promising effects of BIA on body composition , this has not been found in a large body of research. BIA has been shown to underestimate fat mass and overestimate fat-free mass by 1.
This finding is supported by other research on bodybuilders, showing that BIA underestimated fat mass, and overestimated fat-free mass when compared to the four-compartment model [10].
Research conducted by Jebb et al. The authors subsequently developed a novel prediction equation to estimate fat mass from the same Tanita bioimpedance analyser, with the four-compartment method as a reference. However, later research found that this equation also failed to outperform the Tanita manufacturer equation, and resulted in wide limits of agreement [12].
Potentially of greater concern to practitioners considering the use of BIA to determine body composition in the applied setting, are the individual error rates of BIA, rather than data on group means. The study mentioned previously on obese subjects [9] reported that in 12 of the 50 participants, BIA underestimated fat mass by 5 kg or more.
This is supported by the findings of Van Marken Lichtenbelt et al. This suggests that BIA may provide data that is not sufficiently accurate for the determination of individual body composition.
The validity of using BIA to measure changes over time A further consideration for the use of BIA is the validity of its use in measuring changes in fat mass and fat-free mass over time, as this may indicate the efficacy of a nutritional or training intervention looking to manipulate body composition.
To revisit the study by Ritz et al. Fat mass was underestimated by 1. Individual error rates were greater than at baseline, with BIA underestimating fat mass by 7. A further study on obese populations [13] showed individual disagreement in body fat measurement between BIA and the four-compartment model was high.
Individual measures of body fat ranged from There are a limited amount of comparisons between BIA and the reference four-compartment model in athletic populations. There is disagreement amongst the limited research available, with only one study suggesting that BIA is suitable for assessing body composition in athletes [15], whereas other research suggests that body fat estimates are much higher in athletes when using the BIA method [16].
The discrepancies between the studies may be due to various issues including differences in methodology, equations, and athletic population.
There are currently no BIA equations for athletes that have been derived from the criterion four-compartment method fat mass, total body water, bone mineral mass, residual mass. This makes the application of BIA in this population difficult, as athletes are likely to possess substantially different quantities of fat and fat-free mass when compared to the general population or diseased populations that current equations are based on.
The reliability of BIA The reliability of BIA the reproducibility of the observed value when the measurement is repeated is also important to determine single-measurement precision, as well as the ability to track changes over time.
A plethora of research has indicated the importance — and potentially the inability — of standardising BIA measures to sufficiently account for various confounders. The mean coefficient of variation for within-day, intra-individual measurements, has ranged from 0.
Standard measurement conditions may vary depending on the machine type e. hand-to-hand, leg-to-leg, supine vs. standing, etc. Other factors which may impact the BIA measurement and should therefore also be standardised are [16]:. The standardisation of hydration status is clearly of importance for BIA, as the method is reliant on estimations of total body water to ascertain fat-free mass.
For female athletes, difference in hydration status during menses may significantly alter impedance [17] and should be a consideration when assessing female athletes with BIA. Saunders et al. hyperhydrated or hypohydrated , indicating that even small changes in fluid balance that occur with endurance training may be interpreted as a change in body fat content.
In addition, eating and strenuous exercise hours prior to assessment have also previously been shown to decrease impedance; ultimately affecting the accuracy of the measurement [19].
The need to standardise eating, exercise, and both acute and chronic hydration changes are clearly important to provide valid body composition estimations. As mentioned previously, there are several issues with BIA measurement that may limit its use in an applied setting.
Methodological limitations of BIA may affect the ability of the method to accurately determine body composition. The primary issues with BIA are:. Sensor Placement One such limitation is the placement of the sensors, and their ability to give readings of total body composition.
As electrical current follows the path of least resistance, some scales may send current through the lower body only, missing the upper body entirely. Similarly, hand-held instruments may only assess the body composition of the upper extremities.
As females typically have a higher proportion of adipose tissue in the gluteal-femoral region [20], it is possible that this would not be represented using hand-held BIA devices. Hand-to-foot BIA devices, however, may allow for greater accuracy, as the current is sent from the upper body to the lower body, and is less likely to be influenced by the distribution of body fat.
Hydration and Glycogen Levels Regardless, all devices are still subject to the same limitations that other BIA devices are. Deurenberg et al. They speculated that changes in glycogen stores, and the loss of water bound to glycogen molecules, may affect BIA estimates of fat-free mass.
In athletic populations, where varying glycogen stores are likely throughout a training week, it is likely that this will lead to some variation in the detection of change in fat-free mass in athletes as glycogen is likely to be affected by both diet, as well as the intensity, duration, and modality of previous training sessions — even with protocol standardisation.
Effect of incorrect measures in the applied setting An important consideration when assessing the individual variation of BIA is the potential consequences that an incorrect reading can have. This can have wide-ranging implications, from assessing the efficacy of previous dietary and training interventions to making decisions on the correct interventions moving forward.
For example, an athlete may be singled out for interventions to reduce their body fat based on their BIA assessment and normative values, yet other methods may suggest that their body composition is optimal.
The primary area for future research in this area is clearly the need for validated BIA equations for athletes in a range of sports and with varying body composition. It is important that these equations are validated using a total-body, water-based, four-compartment method, in an attempt to minimise the measurement error that is found when equations are based on the two-compartment model; such as hydrostatic weighing.
As such, the following areas of research are needed to expand current knowledge on this topic:. To conclude, it is likely that BIA is not a suitable body composition assessment method for athletic populations. The lack of a validated equation for this population, combined with the large individual error reported in overweight and obese populations, suggests that BIA does not provide accurate body composition data for both single-measure and repeated measures.
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Bioelectrical Impedance Analysis BIA Bioelectrical Impedance Analysis BIA can estimate body composition e. Contents of Article Summary What is Bioelectrical Impedance Analysis?
Types of Bioelectrical Impedance Analysis What are the Bioelectrical Impedance Analysis equations? Is Bioelectrical Impedance Analysis valid and reliable?
Are there issues with Bioelectrical Impedance Analysis? Is future research needed with Bioelectrical Impedance Analysis? Conclusion References About the Author. Figure 1. The difference in bioelectrical conductivity between muscle and fat. References Buccholz, C.
Bartok and D. Franssen, E. Rutten, M. Groenen, L. Vanfleteren, E. Wouters and M. Schlager, R. Stollberger, R. Felsberger, H.
Hutten and H. Bergsma-Kadijk, B. Baumeister and P. Sun, C. Chumlea, S. Heymsfield , H. Lukaski, D. Schoeller, K.
Friedl, R. Kuczmarski, K. Flegal, C. Johnson and V. French, G. Martin, B. Younghusband, R. Green, Y. Xie, M. The InBody measure each segment separately and shows the impedance values of all five cylinders of the body at each frequency in the Impedance Section of the InBody Result Sheet.
InBody uses multiple currents at varying frequencies to provide precise body water analysis. When measuring impedance with electrodes, contact resistance occurs.
InBody accounts for contact resistance with strategically placed electrodes to ensure that measurements are accurate and reproducible. InBody measures your impedance independently, so your results are not affected by your age, gender, ethnicity, athleticism, or body shape.
BIA Tech Problem The ability to distinguish between extracellular and total body water is important to identify fluid imbalances related to acute inflammation or edema. Many BIA devices use only one frequency at 50 kHz to measure impedance.
As a result, patients with increased extracellular water may be misidentified as being healthy. InBody uses a combination of low and high frequencies to determine extracellular, intracellular, and total body water.
The use of multiple frequencies allows InBody devices to achieve a high level of precision. Medical practitioners can use InBody for measurements of body composition and fluid status.
Total body water TBW is stored throughout the body and can be separated into 2 compartments:. Early BIA devices used a single 50 kHz frequency to calculate TBW. Therefore, ICW was estimated proportionally based on the ECW. This estimation was used to determine TBW, lean mass, and fat mass.
The estimation of intracellular water was based on the assumption that the ratio of ICW to ECW in healthy adults is about However, individuals with body compositions that differ from conventionally healthy adults, such as elderly, obese or chronic disease patients, often have a higher ratio of ECW.
Thus, in these patient populations, relying on the ICW:ECW ratio could result in significant error. InBody uses multiple frequencies ranging from 1 kHz to 1 MHz to provide precision body water analysis.
Electrical currents interact differently with the cells at different frequencies, which allows the InBody to quantify the different fluid compartments.
Low frequencies are better suited for measuring ECW, while high frequencies can pass through cell membranes to measure ICW and therefore TBW. An accurate measure of TBW and the ability to analyze ICW versus ECW allows for a deeper analysis of individual body composition.
Compartmental water measures can be used to properly quantify and identify changes in fluid balance to reflect nutritional status and fitness progress.
If the starting measurement position changes, the length of the measured cylinder also changes. This directly impacts impedance and introduces error. When the human body comes in contact with an electrode, resistance occurs. To accurately measure the resistance in the human body, it is important to control the measurement location.
These designs can cause measurements to start in the palm, which has a high impedance and can cause inaccuracies, or lead to inconsistent measurement starting points, reducing the reliability of results.
The anatomical design of the hand electrode creates a simple holding position that is easy to reproduce. Utilizing the anatomical characteristics of the human body, when an InBody user grasps the hand grip, current flows from the palm electrode and the electrical energy, or voltage, is initiated at the thumb electrode.
When current and voltage overlap, impedance can be measured. By separating current and voltage into the hand and foot electrodes, the point of overlap can be controlled to isolate the five cylinders of the body limbs and torso and consistently start at the same location on the wrists and ankles for reproducible results.
With this design, the point of measure stays the same even when the user changes the holding position of the hand electrode or the contact points on the hands and feet.
Traditional BIA views the human body as one cylinder. However, the torso of the body needs to be measured separately because its short length and large cross-sectional area mean that even a small measurement mistake can lead to substantial error.
Direct segmental measurement bioelectrical impedance analysis regards the human body as five cylinders: left arm, right arm, torso, left leg, and right leg. InBody independently measures each cylinder to provide accurate measurements for the entire body.
Traditional BIA systems viewed the human body as a single cylinder, using whole-body impedance to determine total body water. One of the biggest problems with the single cylinder method is the lack of a separate torso measurement. The torso has the shortest length and highest cross-sectional area, which results in a very low impedance typically ohms.
Therefore, small errors in torso impedance have significant impact on body composition results. With whole-body impedance measurement, the torso impedance is not observed separately and thus, changes in torso impedance cannot be quantified.
Because of the large amount of lean mass in the torso, small variability in impedance measures can have a drastic effect on how the results are interpreted.
Differences and percentages may vary based on the individual. Some BIA devices avoid the torso measurement entirely. For example, with many BIA scales, only the impedance of your legs and a small part of your torso are measured. Similarly, with handheld BIA devices, only the impedance of your arms and a small portion of your torso are measured.
With this design, the rest of the body must be estimated. In many bioimpedance technologies today , empirical equations are incorporated to compensate for technological flaws, including the lack of torso impedance due to whole-body impedance measurement , single frequency measurements which are unable to differentiate between water compartments , and lack of reproducibility from electrode placement or positioning.
InBody measures body composition without relying on empirical assumptions based on age, gender, ethnicity, or body shape, producing accurate and precise results that are validated to gold standard methods. Put simply, InBody provides individualized feedback for better tracking of progress to help you achieve your goals.
These equations help compensate for the lack of torso impedance measurement and ability to differentiate between body water compartments by plugging in empirical data based on factors, such as age, gender, and ethnicity.
For example, these equations may take into consideration that muscle mass generally decreases with age and that males tend to have more muscle mass than females. This expectation is then reflected in the results. Therefore, the problem with relying heavily on empirical estimations is that your results are predetermined, regardless of your actual body composition.
Testing on the InBody will give a user the same body composition measurements whether that user tests as a male or female because the InBody does not use empirical estimations based on factors of age, gender, ethnicity, athleticism, or body shape in its measurements.
In other words, direct measures of your impedance and water distribution are used to determine your individualized results. Because of its technology, InBody has been found to be one of the most accurate BIA devices on the market.
In fact, it has been found to have a high correlation of 0. InBody devices are used by leading professionals around the world to give their clients results they can trust and track.
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Hit enter to search or ESC to close. Close Search. InBody Technology. Menu What is BIA? The History of BIA Technology The Evolution of BIA through InBody. What is Bioelectrical Impedance Analysis BIA? Resistance When an electrical current is sent through your body, components such as body water, fat, muscle, and bone present varying levels of resistance.
Reactance In addition to the resistance described above, the human body presents another type of resistance, called reactance. The body is composed of trillions of cells, each of which is protected by a cell membrane that separates the inside of the cell intracellular from the outside extracellular environment.
Impedance: The combination of resistance and reactance Impedance is the vector sum of resistance and reactance. The History of BIA Technology. Source: Hoffer, E. Correlation of whole-body impedance with total body water volume. Journal of Applied Physiology, 27 4 , and the Impedance Index.
Image Credit: RJL Systems. Sample empirical estimation equation Source: Schoeller, D. Determination of body fluids by the impedance technique.
IEEE Engineering in Medicine and Biology Magazine, 8 1 , Sample empirical estimation equation Source: Lukaski, H.
Estimation of body fluid volumes using tetrapolar bioelectrical measurements. Aviation Space and Environmental Medicine, 59 12 , Cha creates the InBody Body Composition Analyzer.
Revolutionizing BIA Technology with InBody. Multiple Frequencies. Direct Segmental Measurements. No Empirical Estimations.
Bioelectrical Impedance Analysis Analyzet BIA body composition analyzer estimate body composition bbody. fat BIA body composition analyzer and fat-free mass via a small electrical current. By Charlie Beestone Last updated: September 25th, 16 min read. Bioelectrical Impedance Analysis BIA is able to make an estimation of body composition e. quantities of fat mass and fat-free mass by running a small electrical current through the body.
Nutrition Journal volume 10Article Metabolic rate regulation 35 Cite this BIA body composition analyzer. Metrics details. Compositoin impedance analysis BIA is a simple, inexpensive, quick and non-invasive technique compositjon measuring body composition. The clinical benefit of BIA can be further enhanced by combining it with bioelectrical impedance vector analysis BIVA. This report reflects the authors' practical experience with the use of single-frequency BIA in combination with BIVA, particularly in COPD patients. malnutrition in obese and underweight patients with COPD, water retention is presented.
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