Fat is a special and complex tissue in the human body. It includes subcutaneous fat, visceral fat, and others, and is widely present in various parts of the body. Currently, there are several popular methods for measuring fat percentage: DEXA, BIA, etc. Different measurement methods have their own unique algorithms and produce different results. So far, methods for weighing in water and DEXA (Dual Energy X-ray Absorption method) are called the "gold standard." However, repeat test results with these gold standards also present discrepancies. Therefore, with body component analyses, no instrument can give absolute and correct answers. Household body fat scale manufacturers mostly use the BIA measurement method, but results are also different due to different algorithms. The best thing that users can do is not be concerned about the difference of values between different devices, but rather focus on relative changes of the value measured by the same device over long periods of time.
Sticking with the same assessment system will likely yield a better overall picture of a person's health status. Again, we must stress that relative changes of value are more meaningful than the absolute value of a single measurement.