About body composition measurement

About body composition measurement

BIA （bioimpedance analysis scale）helps to distinguish how body fat, muscles, and body water are distributed in your body tissues, it is widely used to determine your body composition.

When there is too much fat in relation to lean body mass, it is known as “altered body composition.” While many people focus only on weight, altered body composition is known to increase one’s risk for a variety of diseases, including cardiovascular disease, type 2 diabetes, and hypertension.

Therefore, BIA can be a critical assessment of your health.

What is bioelectrical impedance analysis?

Bioelectrical impedance analysis (BIA) or simply body impedance analysis, or bio-impedance, is the measurement of the resistance of biological tissues to the flow of a low-voltage current.

The human body is composed of different types of tissues, which have different levels of electrical conductivity. With a voltage around 70 microamperes (μA), the current will go mainly through the most conductive tissues, such as water or muscles.

By measuring the voltage drop between source and receiver electrodes, BIA determines the resistance level of these tissues to the passage of the current.

How does bioelectrical impedance analysis indicate bia body composition?

Bioelectrical impedance analysis is now widely used in the medical field to distinguish the amount of body water, body fat and skeletal muscle in a body.

The analysis first obtains total body water (TBW). This is the amount of fluid that can be found inside and outside your body cells. For an adult, total body water represents 45 to 60% of total body weight.

The other components—with more insulating properties such as body fat or skin—will be more “resistant,” meaning that they conduct electricity less effectively.

Using ratios of bioelectrical impedance measured at a separate frequency, complex equations then estimate the amount of fat-free mass within the body. The amount of body fat is finally deducted from the total weight.

Beyond body composition

Note: Bioelectrical impedance is also a method used in cardiology to assess pulse wave velocity, another biomarker that determines the stiffness of the arteries to infer cardiovascular health.

How accurate is bioelectrical impedance analysis?

The signal used in bioelectrical impedance analysis is totally safe and painless for both adults and children, but note that bioelectrical impedance is not recommended for people with pacemakers.

On one hand, many scientific publications attest to the reliability, precision and accuracy of the BIA method in providing valid estimates of total body water in individuals.

On the other hand, there is still a need for standardization and consensus on certain factors that may alter the test results. Some of these factors are described in a study published in The American Journal of Clinical Nutrition entitled “Clinical characteristics influencing bioelectrical impedance analysis measurements.”

You may want to know , how can it be a best body fat analyzer or body composition analyser or body analysis machine

Factors that may affect BIA analysis include:

Environment

Changes in the skin temperature due to the environment where the measurement is taken are thought to impact skin surface impedance, as detailed in a science paper published in the Journal of Applied Physiology: “Controlled ambient and skin temperatures should be included in the standardization of BIA measurements.”

Hydration

Because muscles are largely composed of water, dehydration decreases the amount of fluids and electrolytes that might lower the conduction of these tissues. As a result, fat-free mass is more likely to be underestimated. Hydration levels vary widely throughout the day, which explains why consistency is an important factor in accurate BIA estimation.

Age

A 2017 study published in the Journal of Bodywork and Movement Therapies, “Body composition estimation in children and adolescents by bioelectrical impedance analysis: A systematic review,” demonstrated a perfect correlation between BIA-based body composition estimation in children with reference methods. However, fat-free mass is still often underestimated in children.

Massive obesity

Because the equations that interpret the fat-free mass based on total body water results rely on reference population segments, the body composition estimate might be inaccurate for people considered to be overfat. A study entitled “Evaluation of visceral fat in massive obesity” indicated that an “underestimation of fat mass in obese subjects, and the error becomes greater with increasing BMI.”

Metal implants

People wearing metal implants may experience an underestimated body fat reading. However, this reading will remain constant over time, so they can successfully track their changes in body composition.