The principle of human body fat scale is that muscle contains more water such as blood and can conduct electricity, while fat is not. 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 as to judge the proportion of fat in body weight.
Extended data:
At present, there are many methods to measure human body composition, especially human body fat, mainly including underwater weighing method, skinfold anthropometry, bioelectrical impedance analysis (BIA) and so on. In addition, there are dual-energy X-ray absorption (DEXA), computed tomography (CT) and magnetic resonance imaging (MRI), which have developed rapidly in recent years.
However, these methods need expensive equipment and professional training, and patients are vulnerable to radiation, so they are not suitable for home use. BIA method is convenient to use, accurate in measurement results and relatively low in price, which is favored by consumers.
According to the theory of BIA (Bio-electrical Impact Analysis), BIA is a technology to design and estimate body composition according to different conduction characteristics of different body tissues. When a current with a frequency greater than 50kHz is applied to the body tissue, the current can pass through the extracellular fluid. But part of the current will be absorbed by the cell membrane (resistance, R); Part of the current slows down because the cell membrane is temporarily charged, which is the reaction. Impedance (z) is the sum of resistance and resistance, and usually resistance accounts for more than 90%.
According to the above principle, the electronic fat scale measures the biological impedance by using the electrode pads on the scale surface to contact with the legs of users, and then based on the input user data and the measured human body resistance, we can use the formulas obtained from a large number of experiments to accurately measure human body components, such as the percentage of human body fat, the percentage of human body water, the percentage of human body muscle and the weight of bones.
References:
Baidu encyclopedia-human body fat scale