The most important principles are as follows: eat a balance of food types and a wide variety of individual foods; get most of your calories from natural, unprocessed foods; eat the same number of calories you burn (once you've reached your ideal weight -- it's normal to lose weight in the first weeks of training); eat for consistent energy levels throughout the day; and drink plenty of water.
Endurance athletes do require a more carbohydrate-rich diet, however. As a triathlete, you should get about 60 percent of your calories from carbs, 25 percent from healthy fats and 15 percent from proteins.
And there's one area of nutrition that is supremely important to the endurance athlete: nutrition during and after workouts or races. What you eat and drink during and after workouts has a tremendous impact on how you feel and perform during workouts, how quickly your body recovers following workouts and how quickly you gain fitness.
In particular, proper recovery nutrition is all the more important after a race when muscle fuel depletion and tissue damage are severe.
There are five key nutrients that your body needs during and immediately after workouts or an event: water, electrolyte minerals, carbohydrate, protein and antioxidant vitamins. Let's take a closer look at them.
Water and electrolytes
During exercise, body fluid comprising water and electrolytes (sodium, chloride, magnesium and potassium) is expelled from the body through sweating. The more body fluid you lose, the more your body heats up, causing you to feel and perform worse. Sweat loss can also lead to muscle cramping and other problems.
Consuming a sports drink containing water and electrolytes during exercise is an effective way to limit fluid losses and maintain a higher level of performance during workouts. Try to drink four to eight ounces every 10 to 12 minutes during all workouts lasting 45 minutes or longer. But be aware that even at this rate it's not possible to restore water and electrolytes as quickly as they are lost during moderate- to high-intensity exercise, especially when it's hot. So even athletes who are conscientious about hydration always complete their workouts in a state of fluid deficit. This phenomenon is known as "involuntary dehydration."
In order to ensure adequate restoration of water and electrolytes, in the first two hours after exercise you should consume 1.5 ounces of water and/or a sports drink for each ounce of weight loss incurred during the exercise session. If you choose to drink only water, be sure to supplement it with electrolyte-rich foods like fruits or vegetables.
The primary fuel source for moderate- to high-intensity exercise is glycogen, a sugar that is stored in the muscles and comes from dietary carbohydrate. The longer exercise continues, the more depleted the body's supply of this energy source becomes. Have you ever felt like you just completely ran out of gas in a workout? That's glycogen depletion. It's possible to slow the rate of glycogen depletion through the intake of a sports drink containing carbohydrate during exercise and thereby greatly extend endurance.
After exercise, the sooner you begin to replenish muscle glycogen by consuming carbohydrate, the better. This is because, following exercise, the muscle cells are much more receptive to insulin, the hormone responsible for transporting glucose through the bloodstream to the liver and muscles where it can be stored as glycogen. The body can synthesize glycogen two to three times as fast during the first hour or so after exercise than it can at other times.
How much carbohydrate is needed? As a general guideline, athletes should try to consume about one gram of carbohydrate for every two pounds of body weight during the first hour after exercise.
Most or all of this carbohydrate should be high-glycemic, because high-glycemic carbohydrates stimulate greater insulin release and are therefore delivered to the muscles and liver more quickly than their low-glycemic counterparts. Examples of high-glycemic carbohydrate food sources are bagels, baked potatoes, bread, Cornflakes and raisins.
Although not a preferred fuel source, protein is used to produce some energy during strenuous workouts when carbohydrate fuel runs low. Also, the normal process of protein building is virtually shut off during workouts.
Because protein is an important structural element of muscles, protein breakdown during exercise leaves the muscles in a weakened state afterward. Most sports drinks do not contain protein.
In order to properly recover from and adapt to this particular training stress, athletes must act quickly to rebuild muscle protein. Timing is as important for protein rebuilding as it is for glycogen replenishment, and for the same reason. Insulin is responsible for delivering both glucose and protein to muscle cells -- and the muscle cells are extraordinarily sensitive to insulin during the first two hours after exercise.
How much protein do you need? About one gram of protein for every four grams of carbohydrate is optimal.
A major cause of post-exercise muscle soreness and weakness is oxidative stress, or free radical damage. Oxygen is a highly reactive molecule -- a free radical. During intense exercise, an athlete's rate of oxygen consumption increases dramatically. Many of the individual oxygen molecules consumed during exercise try to become more stable by pilfering an electron from living tissue, often a muscle cell membrane, and thereby damage the muscle cell.
Fortunately, antioxidants such as vitamin E are able to protect body tissues by neutralizing free radicals. Antioxidants are plentiful in many fruits and vegetables, and a growing number of sports drinks and recovery drinks contain them as well.
Matt Fitzgerald coaches runners and triathletes and is the author of Triathlete Magazine's Complete Triathlon Book, Runner's World Guide to Cross-Training, and The Cutting-Edge Runner: How to Use the Latest Science and Technology to Run Longer, Stronger, and Faster.