How the body tester operates determines the reliability of the body fat tester
As more and more people join the fitness army, the term “body fat percentage” has become popular. Body fat percentage refers to the proportion of body fat weight in the total body weight, also known as body fat percentage, which reflects the amount of body fat in the body. In the market, various body fat scales and body fat meters are selling well, and even related apps have been developed, all claiming that they can accurately measure the fat content of the human body. But are these instruments for detecting body fat accurate?
The measurement method is different, the difference is obvious
The author has noticed that most of the body fat meters on the market use the principle of human body impedance to measure the fat ratio. The technical term for this method is called “BIA”. The principle is that adipose tissue does not conduct electricity due to low water content and muscles and other cells Tissues have good electrical conductivity due to their high water content, so the ratio of fat to other tissues is estimated based on the electrical impedance of the human body.
At present, the more accurate body fat measurement method recognized worldwide is the “DEXA” (Dual X-ray Absorption Measurement Method) method. Different from the “BIA” measurement method, this method divides the body into a three-interval model to measure the content of body adipose tissue, non-fat tissue and bone.
A study conducted by the Shanghai Institute of Physical Education showed that male testers between the ages of 20 to 29 and 50 to 59 years old use the “DEXA” method to measure body fat, which is better than a certain brand of body fat meter (BIA measurement). Method) The value is small; male testers between the ages of 30 and 49, the value measured by the “DEXA method” is larger than the value of a certain brand of body fat meter (BIA measurement method). For female testers aged 20 to 59, measured by the “DEXA” method, the value is greater than that of a certain brand of body fat meter (BIA measurement method).
It is not difficult to see that for testers of different ages and different genders, there is a big difference between the results measured by the “BIA” body fat meter and the results measured by the DEXA method.
Different manufacturers have different body fat meter measurement results
“The data measured by the body fat meter and body fat scale are only a rough guide.” According to Yang Yong, an associate professor of the School of Electrical Engineering of Huazhong University of Science and Technology, some of the common body fat meters on the market hold two electrodes with both hands, and some use both feet. On both electrodes, the current forms a loop in the human body. However, the human body is a very complex object, and the conductivity of each part changes with the continuous change of water content and mineral content.
Jiang Chongmin, a researcher at the National Fitness Monitoring Center, told the author that in scientific research, it is recommended to use the “DEXA method” to measure body fat percentage. This method is relatively accurate, but the cost is also very high, the price of a set of instruments is as high as one million yuan. Most of the common body fat scales and body fat meters on the market use the bioelectrical impedance method (BIA) to measure. The accuracy of the values of the instruments produced by different manufacturers due to the different number of electrodes, different samples and reference systems for establishing evaluation standards There are also certain differences.
Which method is simple and reliable for measuring body fat? Jiang Chongmin introduced that citizens can use the BMI formula to conduct self-tests. BMI formula method: body fat rate = (1.20 × BMI) + (0.23 × age)-(10.8 × gender)-5.4. When the gender is male, the gender value is 1, and when it is female, the gender value is 0. Knowing your weight and height, you can estimate the fat percentage. [Body mass index BMI = weight (kg) ÷ height 2 (m)]