The diet plays a key role in athlete's training and recovery. Depending on the intensity and duration of the activity, 3 bioenergetic systems can be engaged at varying ratios: anaerobic alactic, anaerobic lactic and the aerobic system. Muscles use carbohydrates stored in form of glycogen as their primary energy source. Adequate dietary carbohydrate intake is important for glycogen re-synthesis. The glycemic index and the load are values which we assign to foods based on the speed at which they elevate the blood glucose level. Muscles use proteins from food as a source of amino acids, building blocks which they utilise for the synthesis of their own proteins, for the purpose of regeneration and growth. When choosing foods, amino acid composition is of key importance. In the context of sports nutrition, fats are important for maintaining hormonal balance, healthy bones and the immune system, but also as a form of energy storage. Attention should also be paid to proper hydration due to the negative effect of dehydration and hyperhydration on sports performance. Vitamins and minerals are essential components of virtually all body processes. Lack of any vitamin or mineral will negatively affect the sports performance as well as general health. Calcium, iron and vitamin D are among the most common micronutrient deficiencies. In today's highly competitive world of sports, more and more athletes turn to sports supplements such as protein isolates, creatine and caffeine in order to improve their performance and gain advantage over their opponents.