Obesity is a condition involving excess body fat, and measuring body fat is an ideal way to assess whether someone is obese or not.
Fat can be divided into subcutaneous fat and visceral fat. Some people, especially women, have a high percentage of subcutaneous fat and low visceral fat, while others have the opposite. It’s worth noting that having low body fat is not necessarily better: the body needs a certain amount of fat to maintain various functions, including hormone levels, metabolic function, and the normal operation of body organs such as the brain, bone marrow, nerves, and membranes. Women with low body fat may also experience amenorrhea, and it takes more than 20% body fat to recover menstruation.
DXA (Dual-energy X-ray Absorptiometry)
The most accurate method for measuring body fat is currently DXA, which uses X-rays to measure body fat. The principle is to use two low-energy X-rays to penetrate the body, and the computer calculates the percentage of fat, muscle mass, and their percentage by the degree of X-ray attenuation.
Although DXA is the gold standard for measuring body fat, it also has the following disadvantages:
It generally cannot distinguish between subcutaneous and visceral fat.
The process involves a small amount of radiation.
It may not be able to accommodate testers with abnormally high BMI.
It is expensive and not widely available.
Bioelectrical Impedance Analysis
Another method is bioelectrical impedance analysis, which uses electrical current to measure body fat. Bioelectrical impedance analysis can measure visceral fat and is a more common and widespread technique than DXA, making it suitable for measuring body fat in the general population. However, it also has disadvantages: there are differences between different measuring devices. The accuracy and repeatability of bioelectrical impedance analysis depend on its equipment, technical software, and the condition of the tester (such as whether the body has enough water), and some measurement techniques are not very accurate, which can lead to errors in the results, such as before and after eating.
Which of these four methods is better? If you want to evaluate a person’s risk of obesity, BMI is a good place to start. DXA and bioelectrical impedance analysis provide detailed information about body composition, including fat and muscle mass and their percentages. They are suitable for extreme muscle mass individuals and can help in clinical research and treatment. To examine the risk of complications associated with obesity (including metabolic and cardiovascular diseases, and dysfunction of adipose tissue), abdominal and visceral fat are still the most relevant indicators, and waist circumference can provide related information. By using multiple methods, you can have a more comprehensive understanding of your obesity risk and prevent it from happening.