Stepping onto a body composition monitor instantly reveals your body fat, muscle mass, and more. But how does it actually measure all of this? Here, we take an in‑depth look at the science behind it.

INDEX
1. Why simply standing on a body composition monitor can measure your body composition
2. Tanita’s technology for achieving even higher measurement accuracy

1. Why Simply Standing on a Body Composition Monitor Can Measure Your Body Composition
Tanita body composition monitors work simply by stepping onto them thanks to a technique called Bioelectrical Impedance Analysis (BIA). By combining your pre‑entered details—such as height, age, and gender—with your measured body weight and electrical impedance (your body’s resistance to a tiny electrical current), the device can estimate your body composition.

Bioelectrical Impedance Analysis (BIA)
BIA estimates body composition by sending a very small, harmless electrical current through the body and measuring how easily it flows—this is the electrical resistance.
This method takes advantage of two key characteristics:
• Fat conducts almost no electricity.
• Muscle and other tissues rich in electrolytes conduct electricity well.
Electrical resistance differs based on the cross‑sectional area of muscle (a good conductor).
• The larger the cross‑section, the lower the resistance.
• The smaller the cross‑section, the higher the resistance.
By combining the measured resistance with your height (to estimate muscle length), the monitor calculates muscle mass. Using this muscle mass, your body weight, your personal profile, and large sets of statistical data, the device then estimates how much fat your body contains.

How Resistance Reflects Body Fat and Muscle
Using this principle, even people with the same height and weight can show clear differences:
• People with more fat (less muscle) → higher electrical resistance
• People with less fat (more muscle) → lower electrical resistance
By analyzing these resistance differences, the device can determine your body composition—just from standing on it.

2. Tanita’s Technology for Even Higher Measurement Accuracy
Although BIA measures how easily electricity flows through the body, the electrical properties inside muscle (specifically the electrolytes) vary from person to person, influenced by factors such as age and exercise habits. Traditional BIA methods could not capture these individual differences.
Tanita solved this by developing two advanced technologies:
• Reactance Technology
• Multi‑Frequency Measurement
These innovations allow the device to reflect electrolyte-related differences more precisely, enabling highly accurate body composition measurement compared to conventional BIA.

Multi‑Frequency Measurement
In biological tissue, the path electricity takes depends on the frequency of the current:
• Low-frequency currents cannot pass through cell membranes, so they only flow outside the cells.
• High-frequency currents can pass through cell membranes and flow both inside and outside the cells.
By using multiple frequencies, the device can gather detailed information about both extracellular and intracellular spaces—resulting in far more accurate readings.
(Insert illustration of multi-frequency measurement)

Reactance Technology
Biological tissues consist of cells filled with intracellular fluid, surrounded by extracellular fluid. Electrically, these components behave differently:
• Intracellular & extracellular fluids → act as resistors (resistance)
• Cell membranes → act as capacitors (reactance)
When represented as an electrical circuit, the components form a model like the diagram shown.
Traditional impedance measurements could only capture a combined value of resistance and reactance. Tanita’s Reactance Technology measures these components separately, which:
• Provides deeper insight into cellular-level conditions
• Captures individual differences more accurately
• Reduces the impact of daily fluctuations in body water
In short, Tanita’s advanced techniques significantly enhance measurement reliability.