As ultra-endurance races continue to rise in popularity, it is critical that athletes understand how to nourish their bodies with proper amounts of calories from carbohydrate, protein, and fat. The importance of carbohydrate for fueling endurance exercise and protein for recovery is well established; however, the role of fat is debated. Specific amounts of carbohydrate per kilogram of body weight are recommended for before, during, and after ultra-endurance exercise. Total grams of protein per day and after exercise are established. After carbohydrate and protein needs are determined the balance of calories typically come from fat. Using fat for energy during endurance exercise is not a new concept, but continues to be studied as way of fueling while sparing muscle glycogen.