Along with carbohydrates and proteins (protein), fats belong to the group of indispensable nutrients. They serve as the building material of body cells. Fats are also suppliers of vital free fatty acids (FSS) and carriers of fat-soluble vitamins (A, D, E). A distinction is made between unsaturated and saturated fatty acids. Of greatest biological importance are the essential polyunsaturated fatty acids (e.g. linoleic acid), which the organism cannot produce itself. For the athletically active, they are performance-enhancing with their vitamin E content.
Along with carbohydrates, the breakdown products of fats, the free fatty acids, are an essential energy supplier for the muscles at rest and during exertion. For athletes, they are a non-exhaustible source of energy. However, the ability to mobilize fat energy, the fat metabolism, must be specifically trained through appropriate training (basic endurance training).