Very low-carbohydrate diet or ketogenic diet has long ago been confirmed to be an effective therapeutic approach for epilepsy, then it became widely known as an effective method for treating obesity, and in the last decade, numerous studies revealed the evidence of the therapeutic potential of the ketogenic diet in many other pathological conditions, such as neurological and neurodegenerative diseases, cardiovascular disease, metabolic syndrome and diabetes. This thesis summarizes the selected effects of ketogenic diet on human health and explains anticipated mechanisms of its therapeutic effects. Since mentioned diseases have a chronic and lifelong character, any type of nutritional intervention with proven benefits, that might reduce dependence on pharmacological therapy, improve treatment outcomes, and reduce side effects, should be included into future treatment recommendation. Clinical use should be conducted according to standardized protocols and under professional supervision. For now, the level of evidence on the efficiency of ketogenic diet is promising, but insufficient for it to be included into standard treatment protocols so the current real clinical benefit is small. Therefore, it is important to encourage further research and debate about the role of different nutrition patterns, including ketogenic diet, on the overall health of the individual and the population.