What, How Much, and When Should You Nutrition During a Triathlon?

Triathlon nutrition is going to look different for everyone. There are no magic formulas that can be applied to all triathletes because, let’s face it, we all function a little differently.

Susan experiences GI issues from ‘Gel X’ while Michael has no problem with it. Frank needs to consume 350 calories per hour on the bike, but Amy only needs 250. And yet they’re biking at the same speed. Why is that?

Nutrition in triathlon must be approached like a science experiment. First we begin with a hypothesis based on truths of nature. Then we test this hypothesis in real time, learn why unexpected results were encountered, and move forward.

The “What”

First and foremost, you need to know what nutrition you’ll be consuming in triathlon training and racing. This will primarily come in the form of carbohydrates.

Oftentimes the carbohydrate required is presented in a number of familiar sources: glucose, maltrodextrin, fructose, etc. (In other words, gels and drink mixes). This is because long durations of exercise deplete our glycogen stores. Glucose, maltrodextrin, and other sugary carbohydrates are the easiest resources to absorb and replenish the glycogen as it’s being lost.

Becky Simon, RD, writing for IRONMAN, notes that it’s best to choose a combination of these sources and in different forms—for example, alternating between glucose and fructose and solids and liquids. This is to increase oxidation, which means improved delivery of fuel to your muscles and less sitting in your gut. A major reason for gastrointestinal (GI) issues.

Also be aware of how much you can carry with you and what type of nutrition will be available on the triathlon race course. You may need to adapt to the limited options.

Lastly, don’t forget to add sodium electrolytes and a small amount of protein to the mix, especially in long course racing and training. Replenishing the salt you lose from sweating helps to prevent unnecessary cramping. Protein aids in muscle building and repair for a faster recovery and in reaping the full benefits of your efforts.

Sample a few different products during various types of workouts in both cycling and running. Find out what’s most palatable and manageable for your stomach first. You’ll also want to discover which products your body most easily absorbs. However, be aware that sometimes benefits or detrimental effects will depend on how much you consume and when.

The “How Much”

Unfortunately, consuming a presumptuous amount of those necessary carbohydrates while racing isn’t a great solution to the glycogen depletion problem. Too much at one time can cause awful GI issues as well as stomach cramping while too little results in an under-fueled body ready to bonk.

This is where the triathlon nutrition hypothesis and experimentation comes into play. You must hypothesize that you’ll need to consume X amount of calories of carbohydrates for each hour of activity. This will be determined by a number of factors:

  • Body weight
  • Intensity and duration
  • Heat and humidity
  • Altitude
  • Mode of activity (cycling vs. running)
  • Metabolic efficiency

All of these variables will determine the “how much” of your hourly nutritional calorie intake. Heavier athletes generally need more calories per hour. Also, higher intensity or durations lasting two to three hours or more generally means a greater demand for calories. Heat and humidity and higher altitudes typically cause the body to require more carbohydrates as well.

In terms of mode of activity, triathletes typically can handle more calories while cycling than they can when running. And those who are of a more elite level or have obtained a clean diet may have a metabolic efficiency that allows them to burn fat for fuel once the carbohydrate glycogen stores are depleted. For these athletes, less overall calories are necessary.

For example, triathletes who have committed to Generation UCAN as a fuel source are attempting to do just this. Burn fat for fuel, eat less calories, and avoid GI issues and blood sugar spikes caused by traditional triathlon nutrition carbohydrates.

However, in general, triathletes want to be consuming somewhere in the range of 150 to 300 calories per hour. But as we’ve learned, the above variables can greatly affect how many calories is the magic number for you.

Initially decide on an amount through research and careful consideration of how the variables apply to you. Then experiment through training. More than likely, you’ll need to tweak your overall calorie consumption until you find the right amount of intake that works for you under varying conditions – environmentally, by activity, and by intensity and duration.

The “When”

You’ll want to intersperse your required calorie intake as much as possible each hour. Also remember that you can take in more nutrition while cycling. As a result, you may want to eat more frequently on the bike than while running.

As reported by Simon, professional triathlete Beth Walsh says, “I like to ‘front load’ my nutrition on the bike with solid calories.” She and others like her might eat every 20 minutes on the bike. With running, on the other hand, you may want to limit yourself to primarily liquids with only an occasional solid snack.

And as Simon also points out, don’t wait to nutrition. Consistency is the key. Even though you might not feel hungry, your body has already begun the process of burning through your carbohydrate stores. You need to be fueling early and often.

TRIDOT TAKEAWAY: Triathlon nutrition should be approached scientifically. Make an educated guess as to what, how much, and when you should be consuming your nutrition and then experiment through training.

TALK WITH TRIDOT: Have you dialed in your perfect triathlon nutrition plan yet? What products or foods do you use? And how much and how often do you consume them?

JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.


Simon, Becky. “Throw Me a Bar: A Guide to On-Course Nutrition.” IRONMAN. World Triathlon Corporation, 27 May 2013. Web. 30 May 2016.

Dolan, Shawn. “How Many Calories Should I Consume Per Hour?” First Endurance. First Endurance, 30 June 2010. Web. 30 May 2016.

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