Based on data of the cross-sectional bioimpedance study of 819,808 male and female visitors of health centers (representing about 0,6% of the Russian population) by the BIA meters ABC-01 «Medas», an estimates of overweight and obesity prevalence in Russia, and the diagnostic efficiency of the WHO criteria for obesity depending on sex and age, were obtained. An average 15% frequency of incorrect measurements was observed which emphasizes the importance of the development and implementation of the training program on BIA measuring technique and data interpretation.