Nutrition for a half distance triathlon

For a half distance triathlon (70.3) or other 4 to 7 hour event, nutrition can be an incredibly important factor. In shorter distance triathlons you can get away with making some nutrition mistakes, but during a half distance triathlon, it is more likely that you will be punished for nutrition errors. In fact, when you talk to athletes who did not have a good half distance race, they will often mention nutrition as the main reason why things did not go as planned.

In this article, I will briefly discuss the basics, a few general rules of nutrition and some of the most common mistakes. Because the aim is to provide clear basic guidelines, I have simplified a few things. Later when a more advanced plan is developed we can bring in some of the nuances. We can also bring in more of the individual differences between athletes.

Ironman 70.3 nutrition half distance triathlon

Three Main Nutrition Issues

The nutritional issues during a half distance triathlon are:

  1. Running out of fuel, hitting the wall, bonking, or just not being able to keep up the intensity during the last part of the race.

  2. Becoming progressively dehydrated to an extent where this will limit performance.

  3. Gastrointestinal problems such as stomach cramps, bloating, etc. that can have a negative impact on your performance.


Your main fuel for an event like this is carbohydrate, especially if you are completing the race closer to the 4 hour mark than the 7 hour mark. Your body stores contain roughly 500 grams of carbohydrate (this is 2000 kcal), not enough to make it to the finish line. In theory it should be enough to get most athletes through the first 3 hours of a 4 to 7 hour race but topping up from the start is essential. Because it takes time for carbohydrate to be absorbed, you need to start early with fuelling to make sure you avoid carbohydrate depletion. Once you run out of carbohydrate stores it is difficult to recover.

Your body stores contain roughly 500 grams of carbohydrate (this is 2000 kcal), not enough to make it to the finish line.

As a general rule, aim for 60 grams of carbohydrate per hour (1,2). This carbohydrate can be in the form of a bar, a gel, chews, or a drink. If you use solid foods, make sure fat, protein and fiber content are low (no more than a few grams). What you use is entirely up to you and your personal preferences. Faster athletes tend to use more liquids and less solids because it can be difficult to chew at high intensities.

To give some idea of what 60 grams per hour equates to, it means that for every hour of the race you would need one of the following combinations: