Ways to measure your bodyfat

PersonalFit Team

We are going to explain what could be used as a more or less reliable method to track your body fat.
As a personal trainer in Tokyo I often face trainees or people being very sure of their body composition, most of the time because a scale told them, but let us dig in and see if they are right to be so sure.

Here is a list of methods to check your body composition.


Smart scales, also known as BIA devices (Bio-electrical Impedance Analysis devices), estimate body composition by measuring electrical impedance through the body. They assume that muscles, which contain more water and electrolytes, have higher conductivity than fat.
However, the accuracy of these scales is limited due to fluctuations in body water content, which can vary throughout the day and affect the impedance measurements.
Factors such as hydration levels, exercise, meal timings, and temperature can impact the results. 
Another point to keep in mind is that smart scales calibrated for Japanese individuals may provide different results for expats or individuals from Western populations due to physiological differences, and vice versa.
We would advise to interpret the measurements from smart scales only as approximate estimates of body fat percentage.

Our recommendations:

Tanita RD-907 and Tanita BC-705N

fitness caliper
 (skinfold caliper)
This is an affordable method that estimate the body fat by measuring the thickness of the skin-fold at strategic places.
To use it, you will need an app or online body fat calculator and choose a method such as the Jackson/Pollock for example.
You can also do the calculations yourself (time consuming).

To note, if you switch Caliper or calculator, the results you get may change.

Our recommendations:

Most affordable

Easiest to use

Professional Caliper ( pricey )

For both smart scales and fitness calipers, the results will remain an estimation. Our advice regardless of the method used, would be to consistently do it first thing in the morning before eating, to remove as much variable as possible. The measurements you find may not represent the exact truth, but they will still inform you of an increase or decrease of you body fat% over time.

Dual energy X-Ray absorptiometry:
Also known as DEXA scan, This technique boils down to a radiography to determine your body composition. A single X-Ray source is used to estimate your bone density to lean mass to fat mass ratio. There are some leading technologies on the market but it is obviously not there for a home use.

Underwater weighting: ( also known as hydrostatic weighing )
Underwater weighing is a simple and logical technique that offers high accuracy. 
In this method, the person's body is weighed both inside and outside a water pool. As fat is less dense than water, the difference in weight between these two measurements allows for a calculation to determine the person's lean mass. This calculation takes into account the buoyancy effect of fat in water. 
Unfortunately this method is not very portable and will have to be done at specific locations.
Potassium ion:
Potassium ion isotope can be found within the cells of active tissues. Determining the total amount of potassium ion is an indirect yet accurate way of determining the amount of lean tissues in a body. That’s obviously only possible in laboratories at the time this article is written. Also quite expensive, compared to methods like underwater weighting, this is much more of a proof of concept.
Nuclear magnetic resonance (NMR):
Does not sound like something you can do in your favorite gym’s locker room, right? Certainly not, that’s hospital level technique taking advantage of the fact that tissues and more exactly nuclei are resonating at a particular frequency depending on their nature. To back the data collection, serious computing power should be used. A perfectly accurate method but not yet to be installed between the lockers and the vending machine.
More portable, this technique could be used by some physicians. Working the exact same way than the echography, the machine is used this time to measure the thickness of the fat layer.
Near infrared interactance (NIR):
This technique is fairly new and studies suggest that this technology should be improved to really be considered as accurate. A probe is placed over the bicep. This probe emits an infrared beam passing through subcutaneous tissues before getting reflected by the bone. Some gym maybe have this pretty inexpensive device but its lacks of refinement pushes us to not advise it as a measurement tool yet.

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