What is bioimpedance? Understand what this exam is for

6 minutes to read

Do you know what bioimpedance is and in which situations this assessment is recommended? If correctly prescribed and properly applied, this type of test can provide a set of valuable information to strengthen health care and guide the adoption of a series of healthy habits.

Such a test is done taking into account body composition — not just weight. Therefore, to learn more about what a bioimpedance assessment is and how it is carried out, in addition to better understanding what its applications are in health care, check out the answers to the main questions on the subject!

What is a bioimpedance assessment and what is it for?

In general terms, bioimpedance is an assessment made with specific equipment, which aims to measure body composition — including the amount of muscle mass, water and fat, for example.

In this way, it is possible to have more detailed and relevant information about the body structure, going beyond the information about weight provided by a conventional scale.

In practice, a bioimpedance test benefits from a physical phenomenon to calculate its results, based on a characteristic of every tissue in the body: impedance.

In short, this characteristic concerns the ability of an object — or part of the body — to impose resistance to an electric current. The higher the impedance, the harder it is for electrical current to pass through.

However, not every part of the body has the same impedance. Due to a number of factors (such as accumulating less liquids, for example), bone mass has a greater impedance, as does fat. In the opposite direction, muscles and water offer little resistance to the passage of electric current.

In this impedance difference, the equipment calculates how much each type of mass represents in the body composition.

How should it be done?

As already clear, the bioimpedance test is performed using specific equipment, which should only be used by trained professionals, in an appropriate environment.

However, the evaluation is a simple, painless and non-invasive procedure. The patient passes through it without experiencing any discomfort.

However, to ensure the reliability of the results, it is important to observe some precautions. The person responsible for the application — in general, a doctor, nutritionist or physical educator — will instruct the patient to fast for water and food for the previous 4 hours.

In addition, it is recommended not to practice physical activities in the previous 24 hours and to urinate before the exam, trying to leave the bladder as empty as possible.

Failure to follow these recommendations will alter the outcome of the assessment, which may render the assessment useless. In addition, the patient must remove metallic utensils from the body, such as watches, bracelets and other accessories.

Once these requirements are met, the professional asks the patient to lie down on the stretcher and remain at rest for about 10 minutes. Then, electrodes are placed on the hands and feet — they will be responsible for emitting the electric current that will assess body composition. The exam itself — that is, the period that the electrical current passes through the body — takes just over 2 minutes.

To monitor the evolution of results, the evaluation can be done every 30 days. In general, the only contraindications for the application of a bioimpedance assessment are pregnant women and those with a cardiac pacemaker.

Why can it be important?

The bioimpedance assessment prescribed by physicians or other professionals is indicated, above all, for monitoring the evolution of nutritional regimens aimed at both weight loss and lean mass gain.

Thus, it can be indicated for a patient with obesity, for example. In this way, the physician, nutritionist and patient will have a more detailed overview of body composition, going beyond the conventional method of calculating body mass index (BMI).

This makes it easier to determine the best plan to combine a balanced diet, regular exercise and other healthy habits to achieve the expected results.

In athletes — or people interested in gaining muscle mass, for example —, bioimpedance can also serve as a basis for guiding the physical education professional on which exercise regimen to recommend.

What can be decided from the results?

By detailing the information from the bioimpedance, those responsible for monitoring the patient are able to provide guidance regarding indicators that may predispose to a greater chance of health problems.

It is possible, for example, to identify excess visceral fat, associated with a number of cardiovascular conditions, cancer and even dementia.

Additionally, the evaluation can identify the accumulation of fat in certain parts of the body — such as the belly —, in addition to body changes linked to certain diseases or even the advancement of body composition according to age.

In the end, all of this will serve to provide personalized guidance, always adjusted to the needs of each patient, in favor of a better quality of life.

What care should be observed and what is the importance of the professional?

It is always worth noting that all information obtained from a bioimpedance assessment must be interpreted by a qualified professional. Another recommendation is never to trust the results of evaluations made from homemade scales.

Although some may offer satisfactory results, it is difficult to determine how well those results are calibrated and reflect reality. Therefore, it is not possible to use them as a reference for much.

Therefore, undergoing evaluation by a professional is also important to ensure the use of equipment capable of providing understandable and reliable results.

Above all, when taking into account the impact of obesity on physical and emotional well-being — better understanding what mental health is also involves understanding the integration between body, mind and self-esteem — using bioimpedance data only with the supervision of a health professional makes all the difference to achieve better results, always based on effective methods and supported by evidence.

Speaking of which, check out our exclusive e-book from Clínica Einstein, which addresses the importance of combining food and physical activity to promote quality of life!

Technical review: Alexandre R. Marra, researcher at the Instituto Israelita de Ensino e Pesquisa Albert Einstein (IIEP) and permanent professor at the Graduate Program in Health Sciences at the Faculdade Israelita de Ciências da Saúde Albert Einstein (FICSAE).