Obesity is a major concern not only of the Czech Republic, but of all developed countries of the world. It is therefore a global pandemic, against which it is necessary to introduce effective measures. According to epidemiological studies, the countries of Central and Eastern Europe are among the states with the highest prevalence of obesity. In most European countries, the prevalence of obesity in women is higher than in men, by about 3-6%. But a big issue is childhood obesity, which predisposes individuals to obesity also in adulthood. This results in an increased risk of premature morbidity and mortality due to complications of obesity. In obese children the risk of musculoskeletal diseases and cardiovascular and respiratory systems is increased. Obesity often leads to disorders of sexual development, skin complications and changes in the psyche. According to the World Health Organization, there are about 43 million overweight or obese children in the world. The treatment of childhood obesity is not simple. It is necessary to establish a long-term strategic plan, based on the lifestyle change focused on nutrition and eating habits, physical activity and strengthening the self-confidence of the child. This diploma thesis was carried out by the quantitative research through the secondary data analysis. The research group consisted of children registered at the general practitioner for children and adolescents, Šárka Mičanová, M.D. The main goal of my thesis was to survey the prevalence of obesity and overweight in children at this selected pediatric office. Four hypotheses were stated for the research. Hypothesis No.1, children with a high BMI at the age of 5 years show the signs of obesity also at the age of 15-17-years, has not been confirmed. Hypothesis No.2, in childhood, obesity originating in alimentation prevails over obesity of endocrinological origin, has been confirmed. The hypothesis that obesity prevalence has increased in recent years has not been confirmed. The last hypothesis presuming that levels of biochemical markers in children with overweight and obesity do not differ from those of children with a normal weight has not been confirmed.