A diet that does not have sufficient calories, fluids or macro-nutrients can cause an athlete's performance to suffer due to a lack of energy. It is vital for an athlete to consume the appropriate amounts of calories, protein, carbohydrates and fat to ensure that he or she has optimal energy. Proper nutrition also helps the body repair itself after a hard workout.
As much as 55 percent of an athlete's daily calorie intake should come from carbohydrates. Carbohydrates help provide fuel to the brain and provide energy during a game or performance. Between 12 to 15 percent of the daily calories need to come from protein to help the muscles recover. Less than 30 percent of the daily calories should come from fat.