How to fuel the Ironman

Race, fuel, race, fuel… timing is key when racing Ironman. And you’ll also need to combat dehydration and hyponatremia, especially if you’re racing in the heat. James Witts explains when to eat and when to drink during the long-distance triathlon


First, breakfast. Though following a similar carbohydrate template to the other distances, you might want to consume some protein to stimulate the post-race muscle process. Take two-time Ironman world champion Daniela Ryf, whose breakfast includes a smoothie containing oranges, berries, vanilla yoghurt, oats and lupine protein. Ryf also consumes bread topped with tahini and jam.


What and when to eat before an Ironman

Again, sip until the start line and squeeze out a pre-swim gel hit. During the race, again aim to consume 90g of carbohydrate per hour and begin feeding as soon as you exit the swim. The extra length of time on two wheels offers greater opportunity to consume real food. “Rice cakes are a good option as they contain 75% carbs,” says Bungay. “Also try peanut butter and jam sandwiches in bite-sized chunks or even mashed banana and honey sarnies.” These ‘real’ options are also important to prevent flavour fatigue.

Ironman nutrition: what to carry on the bike

Set a reminder on your watch to feed every 15-20mins. Not only does this sustain energy stores but also helps to tick off the bike. Many elite athletes work through a template of ride, fuel, ride, fuel… Smaller goals to reach the bigger one.

“As for the marathon at the end, for many it’s about survival,” says Furber. “Aim for the 90g an hour but be flexible. It’s such a long race that you need to be. In other words, if someone’s handing out Jelly Babies, maybe grab them! Coke’s also a good choice later in the run.”

Dehydration is the enemy so 500ml of fluid per hour is the norm. You can tolerate 2-3% dehydration but more and studies show your performance will suffer. That said, don’t overdo it as the potential for hyponatremia is greater the longer you race, especially in the heat. Hyponatremia’s when you consume too much fluid and dilute the salt content in your blood.

Hyponatremia: causes and symptoms of low sodium levels

What are the different types of sports drinks and when should you use them?

Electrolyte sports drinks: can you overdose?

Hydration: 5 mistakes triathletes make and how to avoid them

A personalised sweat test from Precision Hydration is useful here. Just remember that your maximal fluid absorption rate is 800-1,000ml an hour. Consuming any more than this isn’t required. This focus on sodium means choosing the occasional salty snack on the bike such as pretzels.

Sweat testing for athletes: is it worth it?

For recovery, the more depleted your glycogen stores, the longer it’ll take for them to refuel, and can take up to 7hrs after an Ironman. So aim for 15-25g protein after you finish. A recent study has also shown 40g of protein before bed will deliver a sustained supply of amino acids during your sleep.


What type of protein is best for triathlon recovery?

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Found this useful? The try:

What to eat during the week before your triathlon

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How to fuel the Olympic-distance triathlon

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