Bioelectrical impedance analysis is an indirect method to evaluate body composition and an effective method to measure and judge the weight loss effect. It is more scientific than just judging the weight loss effect by human body weight. The basic idea is that when a weak AC signal is introduced into the human body, the current will flow along the body fluid with low resistance and good conductivity. The amount of moisture determines the conductivity of the current path, which can be expressed by the measured impedance value. A large number of experimental data show that there is a statistical relationship between human electrical impedance characteristics and human body composition, which is the principle of human body composition measurement based on bioelectrical impedance technology. Combined with the principle of body composition analysis of BIA method, a method for detecting body fat content and distribution based on BIA method is proposed, and this method is applied to evaluate the weight loss effect of obese people. Verification of the evaluation method of human body weight loss effect based on bio-impedance: By measuring and analyzing the fat content and fat distribution of the subjects before and after weight loss, it is proved that this method is more effective than the method of judging the weight loss effect only by human body weight or body mass index.