Muscle contains more water such as blood, which can conduct electricity, but fat can't. Because the channel conductor of current in the body is muscle, the weight of muscle can be known from the difficulty of current passing, so it can be judged that people with less muscle have a higher proportion of fat.
For example, when an electrical signal with a certain frequency passes through the human body, the "impedance value" of the fat part is higher than that of muscles and other tissues of the human body. When an electrical signal with a safe specific frequency passes through the human body, the electrical signal will change in different degrees due to the different "impedance values" of the human body.
Extended data:
The most common body fat scale uses bioelectrical impedance method to calculate body fat content. The principle of bioelectrical impedance method is that adipose tissue in human body has less water content and poor conductivity, while muscle and viscera have more water content and are easy to conduct electricity.
Therefore, the resistance values of different components in the human body can be measured by very weak current that is harmless to the human body, so as to calculate the content of fat or other body components.
Because the body is "charged", the subjects are required to touch the metal electrode plate of the instrument barefoot. Some users have responded that if the same body fat scale is used and the gender of the tester is changed from male to female, the body fat rate will change.
There is a certain error in the body fat rate because of the limited position where the human body contacts the electrode of the body fat scale. Secondly, eating, drinking and taking a bath will all lead to the deviation of body fat rate measurement, and even the change of standing posture may affect the change of body fat rate scale value.
Baidu encyclopedia-body fat scale
People's Network-Is the Body Fat Scale Accurate? Experts say their data are for reference only, don't take it seriously.