Excessive body weight is an increasingly common problem in highly developed societies. Obesity currently reaches epidemic proportions worldwide and the problem is growing also among children and adolescents. Factors which lead to obesity include malnutrition and sedentary lifestyle, but also the influence of socio‑economic, demographic, environmental, genetic and endocrine factors. Obesity in children and adolescents is a risk factor of cardiovascular, respiratory and gastrointestinal system diseases. It can also be the reason of psychic problems. Obesity is considered a disease which should be treated to prevent its potential harmful effects by reducing patients’ body mass.