Ketogenic diet (KD) is a diet with a high fat content (50 – 65%), moderate protein content (30 – 35%) and a very low carbohydrate content (5 – 10%). The mechanism of action of KD is very similar to the act of starvation, but with the possibility of maintaining an adequate intake of essential macronutrients and micronutrients. The positive effects of this diet were initially described in the treatment of epilepsy in children, and the beneficial effect of KD on weight loss has been well described. Adipose tissue is a seemingly inexhaustible but slow source of energy that the body relies on in the absence of carbohydrates. Adenosine triphosphate (ATP) is called "energy money", and it is satisfied in the body by aerobic and anaerobic processes, depending on the duration and intensity of an activity. Aerobic capacity is the ability to perform work for a long period of time, and is measured by maximum oxygen uptake (VO2max). Anaerobic capacity represents the maximum amount of ATP released in short-term high-intensity activities. A review of the available literature suggests that KD is favorable in professional endurance sports of medium intesnity, but impairs high intensity performance, while in professional strength and explosivness sports it does not yield significant results. The results of the effect on psychological status remain anecdotal. Significant adipose tissue loss was observed, but the mechanism remains unclear. The available literature is scarce and conducted on small samples of participants, which makes it impossible to draw clear conclusions.