In the recent years, an alarming tendency has been observed concerning the growing prevalence of obese and overweight people in populations. This is a worldwide problem, but is observed less often in the societies of African and South Asian countries. The World Health Organization drew attention to the social context of obesity by supporting epidemiological studies and emphasised the problem by, for instance, establishing the World Anti-Obesity Day. Obesity and overweight are risk factors of significant threats for human health, including: metabolic syndrome, type 2 diabetes, atherosclerosis and cardiovascular complications as well as urolithiasis. The coexistence of obesity, metabolic syndrome and urolithiasis significantly increases the risk of cardiovascular events, including myocardial infarction and stroke. Obese patients frequently manifest vitamin D deficiency, which also contributes to metabolic disturbances. Obesity is associated with a greater risk of neoplasia, particularly oestrogen-dependent one. The most common is simple obesity, caused by improper nutritional habits, both in terms of quantity and quality, as well as the lack of physical activity. The causes of secondary obesity are more complex, e.g. in the course of endocrinopathy, central nervous system disorders, genetically determined syndromes and iatrogenic syndromes (following therapies with glucocorticosteroids, oestrogen, antidepressants and certain neuroleptics).