A good nutrition plan includes proper amounts of each macronutrient (protein, carbohydrates, fat). Athletes need to fuel their training and to give their bodies these nutrients to perform, repair and recover properly. On top of this an athlete needs also to think about their overall general health, which includes a strong immune system.
One area that I find is still largely misunderstood even though well studied is the area of protein for endurance athletes. Most of my clients come to me with nutrition regimes that include too much protein and fat and not enough carbohydrates (their main fuel source). There is this fear that we need MORE protein, but in reality, excess doesn't benefit the endurance athlete.
Research indicates that endurance athletes should consume a diet of approximately 55-60 percent carbohydrates, 20-25 percent fats and 15-20 percent protein. This clearly has some flexibility and we need to also consider grams of carbohydrates per kg of bodyweight as well as percentages when making a detailed plan. Also some endurance athletes, such as Kenyan marathon runners, have reported consuming up to 70 percent carbohydrate diets.
However, with the billion dollar diet industry pushing lower carbohydrate and zone-esque like diets, some athletes still seem to have jumped onto the higher protein, lower carbohydrate bandwagon. Whether it is in an attempt to lose weight or simply because media has led them to believe this is what they need to lose weight, it is a mistake. Although we do need protein, it is not the endurance athlete's fuel of choice. These diets are a recipe for disaster for the endurance athlete.
The bottom line for endurance athletes is that carbohydrates and fats are the necessary fuels for energy. In the sports nutrition community carbohydrates are often said to have a "protein sparing effect." What this refers to is that we should eat approximately 55-60 percent carbohydrates in order to spare the protein for its routine uses in the body. Protein is required to make antibodies for the immune system; it builds tissues (hair, nails, skin, and muscle) and amino acids make enzymes and hormones. Protein is also required to make hemoglobin which is needed to transport oxygen to the exercising muscles.
If we do not eat enough carbohydrates, we will have to break down protein within body tissues as a source of fuel. This is very inefficient. When the body has to resort to protein for fuel it will rob the body of protein needed for its many important uses noted above. Protein has a slow gastric emptying rate (stays in the stomach longer) and therefore is not the food of choice while on the bike either (although protein in small quantities in sports drinks is still up for debate).