How Triathlon Nutrition Plans Work

By: Julia Layton
Whether in training or in a race, a triathlete needs to eat more than the average person.
Photo courtesy of the Department of Defense

There's no way around it, 140.6 miles is a long way. Even in a car. On human power alone, it's a long-distance triathlon, and it requires long-term preparation and a highly specialized training program. Part of that program involves nutrition.

Triathlons are races that combine swimming, cycling and running in a single event, each for a different distance. Triathlons come in a variety of distances, but the most common are:


  • Sprint: 16 miles/25.75 kilometers
  • Intermediate or Olympic: 32 miles/51.5 kilometers
  • Half-Iron or simply "70.3": 70.3 miles/113 kilometers
  • Iron or Long Course: 140.6 miles/226.2 kilometers

The famous Ironman World Championship in Kona, Hawaii is an ultra-distance triathlon. The race has a 17-hour time limit, but the top athletes typically take between eight and nine hours to finish (see How the Ironman Works).

Just as different types of cars have different fuel needs, triathletes, and endurance athletes in general, have different nutritional requirements from the rest of the population.

The good-eating basics are the same: a variety of foods from the different food groups (carbohydrates, proteins, dairy, fruits/vegetables), not too much saturated fat, a good supply of all the necessary vitamins and minerals, enough fluids to keep the body going in optimal condition, and an appropriate number of calories going in to cover the amount expended throughout the day.

That's the first place where a triathlete's nutrition plan is going to veer off the common course. Whether in training or in a race, a triathlete needs to eat a lot more than the averagely active person.

A lot more.


Food Intake for Triathletes

A triathlete may need to nearly double caloric intake.
Photo courtesy of the Department of Defense

An endurance athlete's caloric needs are high, evidenced by Michael Phelps reported pasta-and-pizza diet [source: ESPN]. An average 160-pound human being needs between 2,000 and 3,000 calories per day. An average 160-pound triathlete needs between 3,000 and 4,000 calories per day [source: TNO].

For triathletes, eating too little doesn't just mean losing weight; it means a poor finish. If they don't eat enough, it affects performance. A car can't drive without fuel. An inadequate number of calories (and fluids) can result in fatigue and perhaps injury, or maybe just a terrible training session or race.


Performance in both training and racing relies a great deal on taking in the right nutrients. In general, a triathlete needs to pay specific attention to intake of:

  • Calcium: supports muscle and bone health
  • Carbohydrates: the fastest energy supply for muscles with 4 calories per gram
  • Fat: a more concentrated energy source with 9 calories per gram
  • Protein: essential for building and repairing muscle with 4 calories per gram
  • Iron: needed in red-blood-cell and muscle-cell production, as well as the conversion of food to energy (metabolism)
  • Vitamin B complex: needed for metabolism and to produce red blood cells (which transport oxygen)
  • Vitamin C: supports connective-tissue and bone health while also acting as an antioxidant (prevents free-radical cell damage -- triathletes take in more oxygen when exercising, leading to increased production of free radicals)
  • Vitamin E: also an antioxidant
  • Water: transports nutrients and keeps the body from overheating
  • Zinc: supports energy production in muscle cells

Of these items, the ones most specifically tied to endurance athletics are carbohydrates, proteins, fats and water. Triathletes use more of these nutrients and have to make sure they balance activity levels with intake. For an average triathlon training day, Bob Seebohar of the Colorado Center for Altitude Training and Performance recommends:

  • Carbohydrates: 1-10 grams per kilogram of body weight
  • Protein: 1.2 -- 1.6 grams per kilogram of body weight
  • Fat: 1 gram per kilogram of body weight
  • Water: at least 10-12 cups per day

[source: Seebohar]

This balance is key to any successful triathlon nutrition plan. But 3,000 to 4,000 calories per day doesn't mean 3,000 to 4,000 calories of anything. Here's where the real plan begins…


Nutritional Balance for Triathletes

A calorie-heavy diet doesn't mean ice cream morning, noon and night.
Photo courtesy of the Department of Defense

A balanced diet for triathletes looks a little different from that of the general population. The discrepancy is partly in amounts, which we've already talked about. Triathletes need to eat more -- more carbohydrates, more protein and more good fats (not saturated or trans) in order to balance a greater energy output.

But it also may differ in the proportional balance of nutrients, and that can vary by the day. A longer training session means increased energy requirements, and that means increased intake of carbohydrates, the body's quickest source of energy. This is where "carb loading" comes in. It starts several days before the race and involves a major shift in calorie sources.


The purpose of carb loading is to load up the muscles with glycogen, energy derived from carbohydrates, so they're overstuffed when race day arrives. Normally, muscles have enough stored glycogen to maintain about 90 minutes of intense exercise; successful carb loading will increase that by 200 percent to 300 percent [source: MTP]. The added energy helps sustain the more intense and much longer energy output of the triathlon, helping to delay the inevitable muscle fatigue that comes with that kind of expenditure.

To build up glycogen stores without increasing calorie intake (which would cause undesirable weight gain), the nutrition plan shifts into carb-heavy mode. Carbohydrates increase by about 10 grams per kilogram of body weight, while protein and fat grams decrease [source: MTP].

At the same time, training activities decrease in the days leading up to event. As the muscles are resting and putting out less energy, nutritional energy inputs are increasing. The result is a highly energized body on race day.

Still, no matter how much energy is waiting, it won't be enough for the entire triathlon. Triathletes have to eat (and drink) during the race. Nutritional timing during the race, as well as in training and recovery, is critical.


Nutritional Timing for Triathletes

A healthy training diet gives you the strength you need to compete at your best.
Photo courtesy of the Department of Defense

Perhaps the greatest difference between triathletes' nutritional needs and those of regular folks is the timing involved. Eating for a triathlon is just as much about when you're eating as about what you're eating.

A triathlete's nutrition plan doesn't just kick in on race day. It's a daily commitment that begins with training and carries through until well after the race.



During training, nutrition is about balance and quantity: Eating a variety of foods from each food group, and eating enough of them to counter the amount of energy going out. This means adjusting intake on a daily basis depending on training schedule. A six-hour training day requires a greater number of calories than a two-hour training day.

Fluid is absolutely crucial at every stage, and a good way to know there are enough fluids going in is to weigh in before and after a training session. A triathlete should be drinking 24 ounces of water for each pound loss during training [source: MTP].

Race Lead-up

In the days leading up to an event, there's a shift. Three-to-four days before a race, carb loading begins. Fluids also increase. It's important, though, not to overdo the fluids, which can result in electrolyte imbalance. A good way to know fluids are appropriate is to look at the color of urine: It should be very light yellow. Too dark means not enough water, no yellow at all means too much.

The Race

On the morning of the race, typically about three hours before the event, a triathlete eats a large meal consisting of carbohydrates -- at least 200 grams of them -- and at least 16 ounces of non-caffeinated fluids [source: MTP]. A triathlete should be drinking from the time of that meal all the way up to the race.

During a triathlon, energy reserves will have to be topped off, as there is no way to consume enough energy for the entire event beforehand. High-carbohydrate snacks, including supplement bars and gels, will be useful through the race, about 30 grams of carbs per for each hour racing [source: MTP]. It's best to limit them during the jogging portion, though (which is the final leg), since the intense movement of running can cause stomach upset.


Recovery is as important as training and racing -- a triathlon is a huge strain on the body. Muscles need food to recover from the stress. Fluids are essential. Drink 24 ounces for each pound lost during the race, as estimated during training.

Within one and a half or two hours (or even 30 to 45 minutes, according to some endurance coaches) after racing and training, triathletes should consume carbohydrates, including carb-loaded sports drinks. Muscles are still converting glycogen to energy, and they need fuel to do so. The goal is 1 gram of carbohydrate per kilogram body weight immediately after the race, and about 25 grams per hour for the next 24 hours [source: MTP].

While the specifics of timing, balance and intake are important, the overall goal of any nutrition plan, including one for triathletes, is the same: satisfaction of appetite, consistent body weight, high energy levels and a general feeling of health and wellbeing. To this end, daily food logs can be extremely helpful. Every body is different, and it can take trial-and-error to find the best individual triathlon nutrition plan.

It's a lot of time and effort, but the performance spike that comes from fueling up just right can be worth every minute of it.


Lots More Information

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  • Alley, Victoria. "Basic Meal Plan for Triathletes and Endurance Competitors." Examiner. June 5, 2009.
  • Triathlon Training Diet: Endurance Sports Nutrition. Marathon Training Program.
  • Seebohar, Bob. "How Much Should A Triathlete Eat? Tri-newbies Online.
  • Wilson, Janet. "Triathlon Nutrition." Triathlon Training Resource Center.