Endurance athletes have special needs. Run 5 miles a day and you burn an additional 500 calories. If you don't supply enough fuel, you'll run out of gas. Protein, while important for skeletal and biochemical functions, is not a primary source of energy. The American diet is traditionally ample in its supply of protein, so as athletes we probably need not concern ourselves too much about it.
Fats are an important energy source.
The problem is that fats are about twice as dense in calories as carbohydrates. Fat can be defined as a sneaky little substance which happens to make most of what we eat taste a little better. Carbohydrates are the major source of energy. They consist of two types - simple and complex. The simple group is basically sugars.