As a triathlete, your caloric intake and expenditure are apt to be among the highest of any sports competitors. However, there's no such thing as a one-size fits all nutrition plan for the triathlete. Your calorie needs will depend on your body size, which distance triathlon you are training for, and training conditions and intensity.
Race Type and Calorie Needs
Ironman triathletes may consume as many as 6,000 calories daily. If you are training for a sprint-distance, Olympic or half-iron triathlon instead of the ultimate in distance -- the Ironman -- your calorie needs will be lower as you train. The sprint distance usually includes a .5 mile swim, 12-mile bike leg and 3.1-mile run, while the Ironman distance is standard with 2.4 miles swimming, 112 miles biking and 26.2 miles running. Looking at the run alone, on which you burn an average 100 calories per mile, that's a difference of 2,310 calories burned on race day during that leg of the event, or 310 calories versus 2,620 calories. A typical sprint-distance training program can be completed in about an hour a day, five days a week, whereas a beginning Ironman training plan requires 15 to 18 hours a week. The half-iron involves 1.2 miles swimming, 58 miles biking and 13.1 miles running. An Olympic tri features a .93-mile swim, 24.8-mile bike ride and 6.2-mile run.
You need carbohydrates because they are the primary fuel for your body when you participate in endurance events like triathlons, according to the American Dietetic Association. Consuming enough helps you prevent injury and early fatigue. If you are training for a sprint-distance triathlon, you likely need 2.3 g to 3.2 g carbohydrates per pound body weight each day. For a 150-lb. person, that's 345 g to 480 g carbohydrates per day, or 1,380 to 1,920 calories from carbohydrates. If you have a heavier training load such as an Olympic distance, and train at high intensity, you need 3.2 g to 4.5 g carbohydrates per pound each day, or 480 g to 675 g carbs. That translates to 1,920 to 2,700 calories for a 150-lb. athlete. During extreme training and for races lasting longer than four to five hours, you need 4.5 g to 5.5 g carbs per pound, or 675 g to 825 g carbs daily. That's 2,700 to 3,300 calories from carbohydrate daily if you weigh 150 lbs.
Your protein needs also depend on your training regimen. During light to moderate training, you need .55 g to .8 g protein per pound each day. That's 82.5 g to 120 g daily protein if you weigh 150 lbs., which amounts to 330 to 480 calories a day from protein. The American Dietetic Association recommends .7 g to .9 g protein daily when you have a heavy training load. That amounts to 105 g and 420 calories to 135 g and 540 calories if you weigh 150 lbs. Consuming enough protein is essential for muscle maintenance and muscle recovery after workouts, according to "Practical Applications in Sport Nutrition" by Heather Hedrick Fink, et al.
Fat and Other Considerations
As a general rule, about 5 percent of your daily calories should come from fat, according to "Triathlon Training," by Michael Finch. The other 70 percent of your calories during training come from carbs and 25 percent from protein, Finch advises. Eating five small meals a day works better than three big ones. When you eat is just as important as how many calories you take in because you need to fuel up for workouts properly, according to "Ironman: First Triathlon," by Lance Watson, et al. Eat 60 g to 100 g carbs one to three hours prior to a workout. That's 240 to 400 calories. Make this snack high in carbs and low in fat and protein. If your workout lasts more than 90 minutes, take in 200 to 300 calories each hour during your workout, mainly from carbs. Post-workout snacks aid in muscle recovery and help you refuel your glycogen, or muscle energy, stores. Eat within 30 minutes of finishing your workout. Aim for .5 g carbs and .125 g protein per pound lean body weight, approximately 200 to 300 total calories total for most people, advises T.J. Murphy in "Triathlete Magazine's Guide to Finishing Your First Triathlon."