Why traditional BIA is flawed and how we’ve revolutionised body composition analysis

Bioelectrical Impedance Analysis has come a long way since it debuted in the early 60’s. Over the years, we have seen the progression and increase in accuracy and reproducibility as the technology has evolved.


Original BIA, although innovative for it’s time, was extremely flawed.

BIA initially used a single frequency which measured only the extracellular water (the water outside your cells), and it only measured one side of the body.

It was fundamentally flawed in the sense that an assumption was made that one side of the body is exactly the same as the other. We know that is not the case at all. If we look at people that are one side dominant (eg tennis players or a pitcher), you will find that one side of the body can be slightly more developed than the other. So the conclusion was that most of the assessments were based on a guess.


After it was concluded that traditional BIA wasn’t really an effective way of measuring the extracellular water or the intracellular water, they started putting what is called empirical estimations into the equation. What that meant was they used an assumption method based on your inputted data, which generally refers to age, gender and sometimes ethnicity.

As BIA developed, instead of looking at the body as one cylinder they broke it up into 5 cylinders – these cylinders were made up of each individual limb and your trunk. By measuring each cylinder, they are able to independently and effectively measure these areas in order to get a much more precise method.

There are some BIA devices out there that measure on a 5 cylinder method; however, they still use antiquated technology requiring the empirical estimations, that being assumptions based on age and gender, to determine your results, rather than actually measuring you.


Dr Cha invented InBody in the 90’s and conquered these limitations. He went one step further by overcoming the constraints of using empirical estimations in the measurement of someone.

This required vast technology and through this, he was able to eradicate the need for empirical estimations and ensure the InBody device’s measure someone precisely as they are.


InBody BIA uses what we call the impedance, or the resistance, of you.

Small alternating currents are sent through the body which measures the different resistance of the makeup of the body. For example, body fat compared to body water (such as blood) has a much weaker conductivity, which equals relatively high impedance.

If you did a scan 4 times in a row, even though the body is changing slightly, your impedance won’t change much in the small amount of time spent scanning.

If you were to test this by scanning 4 times in a row on an InBody device and changing your age and gender with each scan, you would recognise the impedance wouldn’t change and therefore your measurement wouldn’t change, regardless of the inputted data (age and gender).


The reason InBody requires this information is to display guidelines on the result sheet so you can compare your measurements against suggested ‘normal ranges’ for your age and gender. This has nothing to do with your measurement.

If you tested a generic device by changing the age and gender when scanning, you would have received 4 radically different results, yet your impedance, the resistance of you, has not changed during that time.


This is a really important concept to grasp – these generic devices are using BIA, but they mostly utilise a software program that uses formulas based on age and gender to produce their results. By changing the age and gender, the inconsistent results show that the device is using that information and not actually measuring the user.

As an example, if you added 10 years to your age, then it would provide results based on how it expects your body composition to be if you were 10 years older.

Backed by Science

InBody has hundreds of peer-reviewed scientific studies behind it and as such, it is used by many of the top researchers because it doesn’t use age and gender in the measurement of you.

You won’t find these generic devices within the Medical industry. Nor will you find them in Universities being utilised for research purposes, because you can’t provide facts based on an assumption.

You need to do research by actually measuring something.

And that’s where InBody’s patented technology is unique.

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