Title:. Influence of physical activity on body fat reduction Objectives: The main aim of this thesis is to verify the effect of physical activity on body fat reduction compared with a diet. Methods: Literature search, creation of intervention programs and their implementation, data analysis and graphical presentation of results. Results: Changes in body composition among different groups was not statistically significant. Effect of physical activity on body fat reduction is not confirmed - this hypothesis has been rejected Key words: The exercise program, diet, body composition, gait, energy expenditure and intake, physical activity, motivation, reduction of subcutaneous fat, data collection and analysis, exercise and diet