Background. Timely diagnosis of excess body weight and obesity, by studying the body mass index and body structure parameters, including the characteristics of changes in its fluid sectors, is critical due to the significant spread of obesity and complications it may cause. Objective was to study the distribution of the body fluid sectors and the relationship with the indicators of the body composition among people with excess body weight and obesity on the example of the adult population in Kharkiv. Materials and methods. A total of 485 of Kharkiv residents were studied, all over 18 years of age. Using the method of bioimpedance analysis and according to the body mass index and gender, there was evaluated the total amount of water (L) and total, extracellular, intracellular, interstitial fluids (L). Results. It has been established that in patients with overweight of different degrees, there is an increase in the absolute amount of total water, as well as total, extracellular, interstitial and intracellular fluids. However, the relative content of these parameters decreases. The revealed changes are being intensified with the progression of the degree of obesity. Understanding of these mechanisms is important for the development of personalized approaches to assist the population with overweight. Conclusions. For use in the clinical practice, mathematical formulas are being offered for determining the parameters of body fluid sectors in the urban population of Ukraine, without the use of instrumental methods.