In today’s article you’re going to find out what bioimpedance is, what we’re measuring with this tool, and how reliable it is.
What is a bioimpedance study?
Health professionals have long been aware of two fundamental facts that affect the health of the population:
- The first is that, despite the great social inertia it carries with it, weight alone is not a good marker of health, except in extreme cases.
- The second fact derives from the first: it’s body composition, the relative amount of fat mass and fat-free mass, which really conditions the health, functionality and aesthetics of the patient or client in question.
This is why more and more people are looking for useful and reliable tools they can use to measure their body composition, with the classic BMI taking a back seat.
What does bioimpedance measure?
A bioimpedance scale measures the resistance that a small, painless and imperceptible electrical current has to overcome as it passes through your different body tissues.
That resistance is what the term “impedance” refers to.
This allows you to differentiate between two major subtypes of tissue: fat mass and fat-free mass.
Fat mass, because of its lower water content, is denser than muscle and therefore electrical current encounters more resistance when passing through it.
This category (GLM) encompasses different fabrics, such as:
- Muscle (the most interesting one);
- Bone; o
- Connective tissue (fasciae, cartilage, tendons).
The current used can be mono-frequency (at about 50 kHz) or multi-frequency, the latter being more precise (and expensive) because it allows greater differentiation between body tissues.
Once this small electric current is emitted, the device integrates this impedance or resistance with the individual’s personal information: age, height and gender.
What fat does the electrical bioimpedance scale measure?
The bioimpedance scale does not distinguish between different subtypes of fat.
This is somewhat problematic, because it’s visceral fat that confers the greatest cardiovascular risk to the person.
Of course, it also makes no distinction between other more specific fat subtypes, such as brown fat, the relative percentage of which is very low.
Who is it indicated for?
Anyone can estimate their body composition with a bioimpedance scale.
In this case, the evidence is not clear, so it’s generally recommended not to use these devices or to do so under professional supervision.
In any case, if you’re trying to go beyond weight (and you should), and want a more reliable indicator of your health, buying a scale of this type, from among the many on the market, may be a good option.
Think that even if your accuracy is not excellent, using the same one every time will reveal your tendency to gain, lose or maintain body fat.
Is bioimpedance reliable?
The vast majority of tools that measure body composition and that are available to the average public simply allow you to make an estimate of your body composition.
More precise methods such as DEXA analysis or MRI are only available to research projects or large clinics and centers.
It’s also possible to use plicometry or skinfold measurement, but once again you will be dependent on a properly trained professional.
And why isn’t it accurate?
Our body is not a uniform or symmetrical element, and there are also some factors that can condition the result of your bioimpedance scales:
- Your age, height and gender.
- Recent physical activity.
- Body position.
- Previous hydration level.
- Where you tend to store fat (example: visceral vs. subcutaneous).
- Pregnancy or timing of menstrual cycle.
Tips before the body composition study
Using an electrical bioimpedance scale to measure your body composition, as we have seen, has its drawbacks.
If you have decided to measure your body composition with one of these devices, these tips may help you:
- Always use the same device, as there is a lot of variability between brands.
- Always use the bioimpedance at the same time and in the same conditions (e.g. after going to the toilet, in the same position, fasting, etc.).
- Do not get obsessed with small variations. Instead, take the weekly average as a reference. This will eliminate these oscillations and give you a more realistic trend.
- If you think you may have excess visceral fat, also use other measurement indexes, such as the waist-to-hip ratio, as electrical bioimpedance can give you an unrealistically “low risk” perception.
- Remember that body fat % is only one indicator, and may not be the most important one in the overall computation of your health.
Other markers, such as grip strength, your energy levels, or your performance in the gym, are equally or more important.
- Body Mass Index (BMI) and Waist Hip Index (WHI), two different methodologies to measure our body composition. We tell you all about them at this link.
- Tips for reaching your ideal weight? Just click here.