Physical activity is a pivotal component in the treatment of obesity. An increase in energy expenditure through physical activity in combination with a weight reduction diet intensifies negative energy balance, brings a reduction in fat reserves and, simultaneously, prevents loss of an active body mass. The main aim and significance of physical activity in obese individuals is not the weight reduction itself but its positive effects on factors that represent an increased cardiovascular risk. When prescribing a physical activity to an obese individual, selection of a suitable form, intensity, duration and frequency of load should all be considered. Patient cooperation represents an essential factor in the success of a therapy involving physical activity and is concurrently affected by the presence of other obesity complicating diseases. Also important are other negative factors determined by real life: lack of time, lack of support from family and others, bad weather, inaccessibility of suitable equipment or space or aversion to physical activity as such. When these circumstances are overcome, positively motivating reasoning has to be provided. Communication between physicians and non-medical professional community is the only way to influence physical activity of obese patients and minimise adverse effects. Significant increase in physical activity of the entire population is determined by modifications in physical and social environment and revision of healthcare policy.