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Questions frequently asked by InBody users.
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What is the theoretical background of InBody measurement?

InBody uses Bioelectrical Impedance Analysis (BIA) method for Body composition Analysis.
Impedance is the resistance of an electric circuit or component to alternating current, and in the human body, Resistance determines the Impedance value. Body fat and skin have relatively higher impedance due to weak electrical conductivity compared to muscle and blood. Therefore, two people can have the same weight but a person with higher percentage of body fat will have relatively higher impedance. In particular, InBody measures the impedance in each segments of the body by using the segmental BIA method. (i.e. left arm, left leg, trunk, right arm and right leg)

Is the InBody test really accurate?

Depending on the consistency of the measurement environment and condition, the correlation may be greater or less than R = 0.98 (R² = 0.96).
Reproducibility of InBody is well documented as 0.99 in the papers published in international journals. InBody’s reproducibility is also evaluated in terms of impedance, by testing the consistency of the results when human body electrical circuit models are measured continuously. So all devices are checked whether the difference in percent body fat falls within 1% when repeatedly measured under the same conditions.

It's been said that BIA devices are not very accurate. Can studies conducted using InBody get approved at reviews?

InBody has been developing its own DSM-BIA (Direct Segmental Multi-frequency BIA), achieving an exceptionally high level of reliability by performing body composition analysis only using impedance measurements for each segment of the body which is split into the limbs and the trunk. A number of research papers have been published on the precision of InBody when used on dialysis patients, edema patients, malnourished patients, etc. as well as healthy individuals.


Can a patient with pacemaker measure InBody?

There has also been an overseas report that InBody tests were taken on a group of patients wearing pacemakers in the presence of doctors and clinical engineers. However, in case of the potential issues might occured to patients wearing pacemaker, we put a warning message not to have InBody test. However, if you already had a InBody test, you don’t need to worry about it.

Can a patient with blood glucose monitor measure InBody?

There is no problem with safety as blood glucose monitor is not a life-support medical device like pacemaker. Also, the sensor of blood glucose monitor is attached on the outside of the body and InBody’s alternating current does not flow through the needle.
Regarding the reliability, the needle of the sensor is very small that it does not affect InBody result. The only possibility to affect the sensor is that when InBody test and sensor scanning happens at the same time. However, the possibility should be very low so these can be used together in usual.

Can a patient with cardiovascular stent measure InBody?

Since the stent is not an electronic material such as a pacemaker, there is no problem with safety regardless of the size and insertion position. In addition, although the stent is a metallic material which current flows, its size is very small that it does not affect the impedance measurement. The body composition measurement result can be recognized as reliable.

Can a patient with implant measure InBody?

Implant is not an electric device like a pacemaker, so there is no problem with safety regardless of the size and insertion location.
However it is better to check what it consists of. In case it is non-conductive materials, InBody result is not affected because the current cannot flow through the implant.
Meanwhile, metallic implants are more conductive that it may overestimate the body water and muscle mass. This doesn’t mean that InBody cannot be used. Unless the implant is removed, you can use InBody data to track tendency of the changes in body composition.

Can you measure a patient during IV injection?

Intravenous (IV) needle itself is safe regardless of the size or insertion location because it is not an electric material like a pacemaker. IV treatment, however, affects fluid status of the body that body water is unstable. InBody test is like a snapshot, and it reflects the fluid status at the time being measured. This means that consecutive measurement before and after IV treatment can show different results.

Can a pregnant women take the measurement?

InBody is a product which passed the International Safety Standard IEC 60601-1, and meets the safety standards as a medical device. It has been used in various studies such as postpartum obesity, gestational diabetes, and gestational hypertension syndrome for pregnant women in domestic and foreign research fields. In particular, Dr. Lukaski, a prominent American scholar, said in a paper published in 2007, that BIA technology is safe, fast, and convenient, and it is applicable to pregnant women in a non-invasive way.
In addition, the measurement can be taken at any time, regardless of the initial, middle, and late stages of pregnancy. However, in the early stage of pregnancy, the possibility of miscarriage is higher compared to the middle or late stages, so more precaution is required. As a safety measure the final decision of the measurement should be decided by the mother.

Is InBody test result reliable for amputated patients?

In BWA2.0, you can check whether you have amputation or not. With this function, patients with unilateral amputation can measure InBody.
If it is checked that there is an amputation, InBody is taking this into consideration and calculate results. Result for amputee part will be displayed as 0 which means the value of the amputation site itself cannot be seen. However Total body fat mass, muscle mass, segmental muscle and ECW Ratio except for the amputated part can be used.

The measuring age is up to 100 years old. Is it inaccurate in population over 100 years old?

The age limit for InBody test is set until 99 years old, but it does not mean that only people who’s age is up to 99 years old can measure InBody test. It is just a limit that can be entered in the device for personal information, and age is required only for recording personal information in measurement results. Since InBody does not use empirical variables such as age or gender, it does not affect the measurement results at all.

When is the best time to measure in dialysis patient?

Patient needs to stabilize the water distribution in supine position by lying down for at least 30-40 minutes. It is difficult to wait, but during dialysis, patients lying down for 3-4 hours and it is more efficient to measure in post-dialysis status. After the dialysis, patients’ water volume is close to the normal condition compared to before dialysis.
Therefore, it is advised to take InBody test after dialysis. All other devices such as ultrasound, X-ray are recommended when the patient is close to the normal status. Some device recommend to measure 30 minutes before doing dialysis because of plasma refilling. However, each researcher has different time for plasma refilling and we found the impact of measurement posture is greater than that of plasma refilling.

Is the current flowing in the test harmless to the human body?

InBody test does not harm the human body because it uses minute electric current. The safety of InBody test has been proven and is being used by many medical institutions because the InBody has already obtained the national and European Medical Certificate.

How to disinfect InBody?

Most of the hospital disinfectants use Benzalkonium chloride, polyhexamethylene Biguanide hydrochloride, alcohol as a main component, but InBody’s electrodes, cable and device itself is chemically compatible only to alcohol components such as ethanol and Isopropanol. Therefore, cleaning agents composed of quaternary ammonium components such as benzalkonium chloride or benzylalkonium chloride is not recommended. If frequently exposed, it may cause corrosion and discoloration of the device.
In addition, electronic devices like InBody can be seriously damaged if liquids, cleaning agents and other materials flow into the device. Therefore, it is strongly prohibited from immersing electrodes or cables in disinfectants or spraying liquids directly onto the device. In daily life, gently wipe the electrode and cable or the device with alcohol pads to prevent liquid from flowing into the product.

Testing Protocol

[Before] Do I have to remove my socks or stockings?

If the test is carried out while wearing socks or stockings, the current will not flow smoothly, then the test may not be performed correctly.
The skin must be in direct contact with the electrode for testing.

[Before] What if I do physical exercises before the test?

During physical exercise, a large amount of water is concentrated to the exercised area of the body to quickly supply nutrients and remove waste products. Soreness in the exercised area of the body after physical exercise indicates a high concentration of water in the area, and changes in the distribution of total body water results in errors in measurements made by BIA technology.
In general when temperature and blood flow increase, muscle resistivity decreases. In the process of emitting heat out of the body to lower body temperature that has risen during exercise, blood vessels expand and skin temperature and blood flow increase, which in turn lowers impedance. Therefore, exercise right before InBody test may affect body water and muscles in each part. When using BIA technology, impedance must be measured before exercise to minimize the range of error.

[Before] What if I take a shower or bath before the test?

Taking a shower or bath increases the rate of blood flow. It is a physiological effect to help maintain body temperature, and this affects the measurement of percent body fat. Entering into hot water during a bath temporarily increases body temperature. To emit heat from the body, blood vessels expand to increase blood flow rate, which causes a thermal effect which promotes blood circulation, increases skin temperature and reddens skin color. The higher the water temperature, the faster the blood circulation and metabolism will become.
When stepping into a cooler place after a bath, the body tries to minimize heat loss by contracting the blood vessels and lowering blood flow in the skin. This lowers skin temperature and eventually restores equilibrium to the body temperature. All types of baths including a full bath, half baths and foot baths, induces physiological changes in blood pressure, pulse rate, body temperature, perspiration and skin temperature.
Therefore, even a light shower must be avoided before the InBody measurement. The InBody measurement must be carried out before taking a shower or bath to obtain an accurate body composition measurement.

[Before] How eating or drinking before the test affects InBody result?

Ingesting food increases body weight, and is therefore known to increase percent body fat following the principle of bioelectrical impedance analysis. However, in truth ingesting food decreases impedance and can lower percent body fat. After ingesting food, changes in fluid and electrolytes occur during digestion.
As there is a big increase in blood supply to the digestive system to promote movement of digestive organs, enzyme secretion and absorption of nutrients, blood flow increases greatly and then returns to normal in 2 hours.
This indicates that changes in body impedance is related to ingestion and digestion of food. Therefore, the InBody measurement must be carried out on an empty stomach to obtain an accurate body composition measurement.

[Before] Go to the bathroom before the InBody measurement

Ingesting food (meals and other food), clothing and faeces/urine within our body affect our body weight. Clothing and faeces/urine within the body do not affect impedance, and are considered as fat mass as electricity does not flow through them according to the BIA principle. Therefore, if the InBody measurement are carried out without removing these elements, they will be different from measurements carried out after removing them.
Generally it is known that percent body fat decreases after removing them according to the BIA principle. when measured immediately after going to the toilet, percent body fat decreased as the reduced amount of body weight was used as the amount of fat mass, while the measurements made 10 minutes or longer after going to toilet fluctuated and did not show a consistent pattern of changes. As body weight is an important variable according to the BIA principle, it is best to carry out the InBody mea-surement after going to toilet if necessary.

[Before] InBody measurement during menstruation

Menstrual cycles can cause temporary changes in body weight and body composition due to hormonal influences. Generally, women’s body weight increases during the luteal phase due to the accumulation of total body water. Accumulation of total body water during the luteal Phase or menstrual phase results in an increase of fat free mass and a decrease in percent body fat. However, an increase in appetite and changes in diet pattern due to the tendency to crave sweet or salty food during the luteal phase may cause an accumulation of fat mass, which in turn increases percent body fat.
Percent body fat fluctuates during the luteal and menstrual phases and the measurements varies from month to month even for the same person. In some cases, less changes in percent body fat occurred during the luteal and menstrual phases, which demonstrated the fact that the effect of menstrual cycles on body composition differs depending on individuals. The biggest changes in body com-position occur during the luteal and menstrual phases, and therefore it is the best that females avoid the InBody measurement during these phases.

[During] Do I have to use electrolyte tissue? Can't I use a normal wet towel?

The electrolyte tissue provided with the BWA2.0 is specially designed for optimal measurement, unlike general wipes. It is devised to enhance conductivity between skin and electrode. It is recommended to use electrolyte tissue for accurate measurements.

[During] Keep arms apart from your body during the InBody measurement

InBody divides the body into 5 cylinders: the right arm, left arm, trunk, right leg and left leg, to measure impedance. When there is no gap in the underarm area, the arms are in fact making contact with the upper body, thereby widening the current’s path and consequently, decreasing the impedance. In other words, the trunk’s measurement will include some of the upper arms.
Similarly, if a measurement is carried out while wearing a pair of shorts and the thighs are not kept apart, lower body impedance will decrease. Such differences in impedance measurements lead to errors in body composition measurements.

[During] Keep arms straight during the InBody measurement

The length and cross sectional area of objects influence resistance. Longer length with small cross sectional area has higher resistance than the other. In other words, amount of resistance to the current that runs through a straight cylinder is different from that of bent cylinder. If the InBody measurement is carried out with the arms or legs bent, impedance of each body part decreases as the length of conductor has shortened. This will lead to a decrease in percent body fat measurements.
Therefore, the InBody measurement must be carried out with the arms and legs stretched straight in order to obtain an accurate measurement.

[During] Perform InBody measurement at room temperature to prevent changes in body temperature

When we are exposed to hot or cold temperatures, our body responds by changing body temperature, skin temperature and blood flow. Body composition analyzers including the InBody use BIA technology to measure impedance and the measurement influenced by skin temperature and the temperature of the room.
Generally temperature and impedance respond in opposite ways, and a decrease in body temperature brings an increase in impedance, which results in a lower amount of fat free mass. Temperature of external environments (environments in which measurements were carried out) affects body temperature, skin temperature and blood flow, which in turn influences impedance, therefore, the InBody measurement must be carried out at room temperature of 25~30℃ to obtain an accurate result.

[After] How often should I have a BWA test?

Testing every other week or once a month can effectively track BWA test results for exercise prescriptions, hormonal prescriptions, obesity, and rehabilitation.
It’s good to check up often, but it is also important to keep track of your body’s changes over time through steady tests.
Body composition changes can be seen on the BWA result screen and the BWA Result Sheet.

[After] What does it mean "Check Impedance" on the result?

When you see “Check impedance”, this means the test was not done properly.
Ideally, when frequency increases from 1kHz to 3MHz, impedance should be decreased. Higher the frequency, lower the resistance.
When patient has dry skin or if the electrodes are not attached properly, impedance reversion can happen. Therefore, if you see this sign, please re-do the test.

Result Outputs

How does InBody calculate Basal Metabolic Rate?

InBody uses Cunningham Formula, which is (370+21.6*FFM). The higher Fat Free Mass, the higher the Basal Metabolic Rate.

How does InBody calculate Mineral?

Minerals are mostly in the form of ions in bones, teeth and blood. InBody mineral refers to the total amount of minerals dissolved in bones (Osseous Mineral) and minerals dissolved in body water (Non-Osseous Mineral) .The concept of minerals in InBody are same as the BMC (Bone Mineral Content) measured by DEXA (Dual Energy X-ray Absorptiometry), a standard device for measuring bone density which refers to the inorganic mass in dry bone.
Osseous Mineral provided by InBody is an estimate based on DEXA’s BMC (Bone mineral content). DEXA is a device that provides body composition (Fat, FFM, and, BMC) for each segment using the difference in density of the body composition by irradiating X-rays to the human body. Factors used for estimating Osseous minerals include impedance, FFM (muscle mass), body fat, BMI, and the regression equation for this is not disclosed.
Non-Osseous Mineral can be obtained by using the inclusion relationship of body composition. Non-Osseous Minerals can be obtained by subtracting the total body water and protein from the Fat Free Mass (FFM) to obtain the total inorganic mass and subtract the Osseous Mineral estimated through the regression equation with DEXA.
1) Total Mineral = FFM – (TBW + Protein)
2) Estimation of Osseous mineral through regression equation with DEXA
3) Non-osseous mineral = Total Mineral – Osseous mineral
In an in-house experiment with Dexa and InBody, the primary test (7-66 years old, n = 171) showed a correlation of R = 0.920 and secondary test (1-88 years old, n = 200) showed R = 0.908 in average healthy population.

How Skeletal Muscle Mass calculated?

Since the arms and legs lean mass are composed of skeletal muscle, InBody calculates the Lean mass of the arms and legs first. Then the total skeletal muscle mass is calculated based on several literatures that indicate that the segmental skeletal muscle mass is 75% of the total skeletal muscle mass.
Skeletal Muscle Mass = Sum of Segmental Lean Mass / 0.75
In actual cases, skeletal muscle mass in the Results Sheet is sometimes lower than the value we calculate by the equation above (Segmental Lean Mass / 0.75). It indicates that trunk muscle is relatively less developed than the arms and legs muscle. To avoid such miscalculations, InBody also considers muscle mass distribution in the body and also the ECW Ratio to check over hydration status caused by edema.

How Skeletal Muscle Mass Index (SMI) Calculated, and how can I utilize for sarcopenia?

SMI stands for Skeletal Muscle Mass Index, and it is used to study for Sarcopenia (muscle loss). Nowadays, many researchers use SMI for their Sarcopenia research. SMI calculation varies depending on the researcher but the following three are mainly used.

(1) [Definition of Baumgartner] SMI = Appendicular Skeletal Muscle Mass ÷ Height squared.

In EWGSOP(European Working Group on Sarcopenia in Older People) announced the cut-off value for Sarcopenia (Men 7.0kg/m2, Women 6.0kg/m2) and it is widely used in Europe. Calculation of SMI in InBody is as shown below. The calculated value will also be shown on the Results Sheet.
Segmental Lean Mass(two arms and two legs) ÷ Height2.

How can we interpret ECW Ratio and in regards to the imbalance and circulatory disorder?

ECW Ratio refers to the ratio of extracellular water (ECW) to the total body water (TBW). For healthy people, the intracellular water (ICW) and extracellular water(ECW) have a constant ratio of 62:38, so the ECW/TBW shows a value of around 0.380, which does not change even if large amount water is drunk. ECW/TBW is widely used worldwide as an indicator for edema or severity of diseases. normal range is 0.360 ~ 0.390, anything above 0.390 indicates weak edema, and more than 0.400 is diagnosed as edema.
ECW Ratio, No matter what range the person has, we consider a difference of 0.007 as a significant difference. However, the difference up to 0.004, we usually ask people whether they recognize this difference.

How can we interpret the Segmental Lean Analysis?

The graph above represents the muscle mass (kg), and the length of the graph indicates how much muscles you have compared to the ideal weight. The graph below shows how much muscles you have compared to your current weight in a percentage.
Even if the length of the upper bar graph is within the normal or over the normal range and the length of the bottom bar graph is below the normal range, it indicates that there is insufficient muscle for your current weight. Therefore, Segmental Lean Analysis shows not only the amount of muscle in each segment, but also it helps you to determine whether you have sufficient muscles for your actual weight.

The total amount of Muscle Mass provided on the Results Sheet does not match the sum of the Segmental Lean Mass.

Soft Lean Mass is the sum of body water, protein, and minerals which includes skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle mass is the voluntary muscle that is attached to your skeletal structure which can be moved with your own will and it considers as one of the muscle type.
Total muscle mass is different from the total segmental lean mass because the weight of the head is not reflected in the segmental lean analysis as the current doesn’t flow through the head. In other words, total muscle mass is the heaviest concept that includes skeletal muscle + cardiac muscle + smooth muscle + weight of the head. Segmental Lean Mass is the value excluding head weight from the total muscle mass, and total skeletal muscle mass excludes cardiac and smooth muscles of the trunk. Therefore, the increasing order would be skeletal muscle mass<segmental lean mass< total muscle mass.

What happens when the ECW Ratio is below 0.360?

If the ECW Ratio is 0.360 or less, it is easy to think that the body is in dehydration state. However, it is not considered as dehydration unless by an exceptional cases such as acute dehydration. Dehydration symptoms rarely happens in daily life because people usually try to drink water right away if they are thirsty.
When ECW Ratio is less than 0.360 in InBody test, mostly it’s because the person has lot of muscle resulting in larger muscle cells. This makes the amount of ICW relatively higher. On the contrary, when the muscle cells age, the ICW is relatively reduced and causes the ECW Ratio to increase.

How do you calculate the Segmental Fat Mass?

When the lean body mass is calculated based on the BIA, the body fat mass can be obtained by subtracting the lean body mass from the body weight. However, even if you know the lean body mass (muscle mass) for each segments, you cannot calculate the body fat segmentally since the weight of the segment is unknown. Thus, InBody estimates the segmental body fat mass using a regression equation for the segmental body fat mass measured by DEXA. During the calculation, BMI, body fat mass, percent body fat, and segmental muscle mass are considered as well. The regression equation is confidential.

Can we measure dehydration with InBody?

Dehydration indicates a lack of body water and electrolyte, which can be classified into three types: Hypertonic / isotonic / storage, depending on how much more water or electrolyte (mainly sodium) is lost. As described above, unlike edema, there is no medically defined cutoff value of extracellular water ratio (ECW / TBW) for dehydration.
Also water movement of internal and external cells depend on the types mentioned above. So an absolute evaluation is not possible and difficult to evaluate dehydration using the body water analysis. However, as InBody can measure the actual body water status during the measurement it can be utilized to monitor the changes in the body water.

What does the TBW/FFM tell you?

TBW/FFM Index, which indicates to what extent the lean mass is hydrated. From the point of 4 compartment model, lean mass consists of water, protein, and minerals.

What is Body Cell Mass?

Body Cell Mass is the sum of proteins and intracellular water. It is a useful parameter for assessing the nutritional status of a patient. When a particular disease occurs or nutritional status is poor, proteins and intracellular water decreases. Thus, Body Cell Mass can be a useful parameter for assessing nutritional status in the long-term monitoring purpose in analyzing body composition.

In the Muscle-Fat Analysis bar-graph, what does the 100% for Skeletal Muscle Mass indicate?

A comparison between Skeletal Muscle Mass(SMM) and the ideal Skeletal Muscle Mass for a person of the same height and gender.

If there is an excessive value for ICW, could that be due to more muscle mass?

It is true that a lot of muscle mass can lead to a high value for ICW. However, it does not make a health risk.

How can we calculate the ideal weight?

The ideal body weight is determined on the basis of ideal BMI. The range of normal values for weight is determined by ideal weight as well, and it is within the range of 85% to 115% of ideal weight.

What is the difference between VFA and VFL?

Visceral Fat Area(VFA) estimates the area of visceral fat in cm². Visceral Fat Area(VFA) provides a simplified measure of visceral fat area with a range from 1-20.
Each level is equivalent to 10cm2 of VFA. Therefore, a VFA of 11.3cm² would be equivalent to a VFL of 1, and the maximum value for VFL is Level 20.

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