Fat 

Two categories
Fats can be divided in two categories: saturated and unsaturated fats. Saturated fats are mostly found in animal derived foods: butter, meat, cheese, egg, etcetera.

Unsaturated fats are primarily present in vegetable oils like sunflower oil and olive oil. It is recommended to use mainly unsaturated fats in your daily nutrition.

Second energy supplier
Fat is the second energy supplier for an athlete’s muscles. At low intensity exercise, a muscle will use relatively more fatty acids and less glucose, which will save muscle glycogen. At high intensity exercise, a muscle will relatively use more glucose and less fat. As opposed to carbohydrates, fat reserves are virtually unlimited.