A wide range of biological impedance measurement techniques are used to measure the frequency of excitation signals. The simplest instruments are based on fixed-frequency measurements (single-frequency bioelectrical impedance analysis or SF-BIA), some instruments use multi-frequency systems (multi-frequency bioelectrical impedance analysis or MF-BIA), while the most complex instruments perform actual spectral measurements (bioimpedance spectrum or BIS) within a certain frequency range. There are also many techniques to evaluate the results, the most important of which are bioelectrical impedance vector analysis and real-time analysis.
In practice, people often confuse obesity with being overweight. In fact, obesity and overweight are two different concepts. From the analysis of body composition, overweight can be shown in two situations: one is rich in lean tissue and not much body fat, such as athletes; the other is excessive body fat, which is true obesity. Others have less lean tissue and relatively high body fat, although their weight is within the ideal range. To be exact, these people are also obese; however, these people are often ignored. Only by body mass index to judge obesity, only taking into account the height factor affecting weight, still can not objectively reflect the content of body fat. So body impedance analysis machine can help solve this kind of problem.
For example, it is not appropriate for Asians to judge obesity by body mass index. The detection rate of obesity by bioelectrical impedance method was significantly lower than that by ideal body weight method and BMI method. It can be seen that although there is a significant correlation between body weight, BMI and body fat content, there are still some deficiencies as independent criteria for judging obesity. Therefore, no matter which kind of judgment method, only when combined with the comprehensive evaluation of body fat content can it be more reasonable and scientific.