◎Beijing Science Center
Many people are keen to reduce body fat rate by controlling diet, strengthening exercise, etc., and there are many body fat scale products on the market that claim to measure body fat rate, promoting that they can help people monitor body fat changes and develop better fitness programs. So, are the calculations of these body fat scales really accurate? What is the inevitable relationship between body fat percentage and our physical health?
The most common method for testing body fat is the bioelectrical impedance method
Body fat percentage, as the name suggests, refers to the percentage of the body's fat tissue mass in body weight. There are several methods for calculating body fat rate, including underwater weighing method, ADP method, ultrasonic detection method, bioelectrical impedance method, etc.
The underwater weighing method calculates the body fat rate based on the difference in tissue density between fat and muscle.
The ADP method, fully known as air displacement volume scanning method, measures the volume occupied by the human body in the instrument by putting a person into a special measuring instrument, and then calculates the proportion of fat.
Ultrasonic detection method, that is, the use of ultrasonic waves to detect the fat content in the body, similar to the use of infrared, X-ray and other methods of detection.
The above methods are generally only available in specialized medical institutions and medical research institutes because the operation is more complex and the instrument is not easy to obtain. For ordinary people, if you want to test body fat, the most common method is to use the bioelectrical impedance method, which is also the measurement principle of body fat scales on the market today.
Regardless of the body fat scale, only an estimate of body fat percentage can be calculated
The body fat scale on the market is an electronic scale that can not only measure weight, but also estimate the user's body fat content. Its measurement principle is Bioelectrical Impedance Analysis (BIA).
The body's fat conductivity is very poor and has high resistivity, while muscle, on the contrary, contains more water in muscle, has good conductivity and low resistivity.
When microcurrent passes through tissues such as fat, muscle, bone, and organs in the body, it is subjected to different resistance forces. Therefore, bioelectrical impedance analysis technology is to measure the rate and time of microcurrent passing through the human body to determine the resistivity difference of various parts of the human body, and then calculate the proportion of body fat and muscle.
This technology is used in many body fat scale products due to its convenient measurement and low cost, but it should be noted that the correct operating procedure must be followed when using body fat scale to measure body fat.
The correct measurement method is to take off shoes and socks, stand on the body fat scale that has been turned on with the soles of your bare feet, and then the low-voltage current of the body fat scale will pass through the human body, thereby calculating the body fat rate value of the human body.
In addition, the body fat scales on the market are not only foot standing type, but also handle type. Handle-type multiple handles with metal electrodes attached to the body fat scale. Compared with the foot-standing body fat scale, the handle type body fat scale can measure the bioelectrical impedance of the upper body and lower body in segments, so that the calculated body fat rate will be more accurate.
However, no matter what body fat scale is, it can only calculate the estimate of body fat rate, and cannot be 100% accurate.
Why an estimate? First of all, the body fat scale does not directly measure the fat content in the human body, but estimates the body fat rate through resistance data; Second, the instruments and measurement times we use do not inherently meet the conditions required for accurate data.
In 2003, a professional conducted a BIA measurement experiment to measure body fat rate, and the whole process took 40 minutes each time, and our daily standing time on the body fat scale was only tens of seconds.
In addition, in the experimental BIA measurement, the four-electrode method is generally used, that is, the use of 4 table electrodes placed on the human limbs to measure the bioelectrical impedance of the whole body, while the household body fat scale, the electrodes are all concentrated on the soles of the feet, and the measurement range is relatively limited.
More attention should be paid to the increase or decrease of body fat percentage than the specific value of body fat percentage
So, what is the difference between body fat measurement and weight measurement?
Body fat measurement reflects the percentage of adipose tissue in the human body, which can better reflect the proportion of human body fat.
The area of human fat distribution is very wide, including subcutaneous fat, visceral fat, etc., and excessive body fat rate can cause many health problems and physical diseases, such as fatty liver, heart disease, diabetes, obesity. The fat ratio can reflect certain health problems.
Weight measurement refers to the measurement of the weight of the entire human body, including the total mass of various tissues such as muscles, bones, fat, organs, etc. Weight measurement is usually carried out using a scale that provides a preliminary estimate of the body's weight gain or loss through changes in weight values. However, weight measurement can not distinguish the details of body fat, muscle tissue, etc., and people who are heavy may be more muscular or have higher body fat.
Therefore, body fat and body weight are different indicators to observe human health, and the measurement methods and meanings of the two are different, which need to be analyzed according to specific circumstances.
It should be noted that body fat measurement is more significant in obesity than weight measurement alone, and the significance for weight loss is better than weight measurement alone.
In general, the measurement of body fat percentage can help us have a preliminary understanding of our body fat levels, but we do not need to pay too much attention to the detailed figures.
Compared with the specific value of body fat rate, we should pay more attention to its increase and decrease, so as to understand the impact of our recent diet and lifestyle on the body, and make appropriate adjustments in time.
(Article from WeChat public account Digital Beijing Science Center)