Gustav Iden — Fueling for IRONMAN

Article Long read Sport: Laufen Published: 6 Okt. 2026

Read time: 6 Minuten read

Interview by Ross Lovell
Photographs by Love Ljungström

Ten years ago, Gustav had the freedom to race as an unknown quantity — to take risks without feeling like he had anything to lose. Now that young upstart is one of the marked men — one of the IRONMAN favorites.

But even with a Kona title and a second place in Nice, Gustav’s personal validation exists on the far side of the next win. “I don't feel like I've become who I truly feel I should become, in my own head. I'm still waiting for that definitive win. And I feel like it will come, maybe this year, maybe next year, but I feel like it's on the way.” Perhaps that’s the mindset it takes to stay at the top.

After a couple of challenging seasons, it feels like momentum is on Gustav’s side. A bike course record at the 70.3 world championships is a warning shot to the competition that he is carrying speed and form into Kona. “I wouldn't say it’s a comeback, because that's a strange word.” He never went away.

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Fueling starts with real food.

“There are many different ways to fuel, but what we like to do is go high carb. We’ve tried other things, but it’s kind of stupid to try something different again and again when you just know that high carb is basically the way to go.”

But before turning to the specific composition of sports nutrition to fuel your sessions, Gustav clarifies that healthy training starts with healthy eating at all other times. “The most important thing is just your daily nutrition. You can’t fuel away a bad breakfast. If you’re not eating your normal meals, it’s hard to adjust just by drinking sports nutrition. So it’s a decent-sized dinner with a lot of carbs, a good breakfast and lunch. That is by far the most important.”

The fundamentals of fueling are not simply about supporting the body to complete the demands of a specific session, it extends into recovery and beyond. Failing to fuel a hard session sufficiently could the deplete the body and extend the recovery period, making future training harder or less effective. Gustav notes that, for triathletes, this is crucial.

“I fuel on most sessions, but I also train three times a day. If I go into a minus in one session, it’s hard to refuel for the next one.”

Understand what works — and what doesn’t.

Repetition is the mother of learning. To see what sessions and practices lead to the strongest progress and training adaptations, Gustav has established a streamlined training protocol. “One of the things we've changed these last few years has been to keep the weeks a lot more simple. For example, we do smaller variations of the same sessions. From the outside it seems kind of boring, just doing the same, but from the inside you quicker feedback on what's working and what's not.”

While his approach to an IRONMAN has changed very little — consistent training without getting sick — Gustav acknowledges that technology has come much further. “The fueling bit has been revolutionized, and how much we are pushing the grams per hour. I think that's a big game changer.” Ultimately, it’s the fueling that has become race-defining — almost a fourth discipline of the sport. “I think fueling in racing is win or lose. And it’s not win or second place, it’s win or DNF. If you’re not careful with how you fuel, you’re not going to win.”

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Put your fueling into practice.

Training is not just about putting in the miles, it’s when you practice and experiment with all elements of a race. Fueling matters. Always try and practice your fuel strategy before you get to the start line because, in the race, situations can change quickly, from control to discomfort, or even depletion. Gustav knows the important role that race simulation plays when preparing for an IRONMAN.

“Try to do at least one session, or one weekend, that is pretty close to race expectations. Maybe the whole swim distance at race pace on the Saturday, with a bit of a hard bike. Then some bike and close to a half Ironman run on the Sunday, where you try to get in all the carbs per hour you’re planning to take on race day. That is a really good way to set your expectations correctly.”

One crucial piece of advice is to complete your fuel plan for every session. Not only will that help with gut training and carbohydrate tolerance, but it will also ensure that your glycogen stores are topped up and ready for ongoing training. “My normal recommendation is one bottle of Drink Mix 320 per hour — 80 grams of carbs. If you’re riding two and a half, three hours, bring three bottles and drink all three of them. Don’t just plan on drinking them — actually drink them. You’ll have a way better experience on the run.”

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Training with Gel Mix.

Gustav and his training group do most of their long sessions without a follow car. And for high-carb training that can create logistical complexity — everything they need for a four-hour day goes with them. That’s where Gel Mix comes in. Trusted Hydrogel Technology in a format that suits the demands of high-volume training.

“Gel Mix is nice for our IRONMAN prep sessions, especially on the run. We’re usually pretty self-sufficient, so there aren’t many people following us around. That’s just how we like doing it. Bringing Gel Mix is an easy way to get 120 grams of carbs in a pretty accessible way.”

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Gel Mix on race day.

Practicing the logistics of fueling in long training sessions makes racing easier too. If it works in training, it’ll work in a race. Fueling is always personal, and Gustav chooses to use Gel Mix in his aero bottle.

“It can hold almost 240 grams [of carbs] in quite a compact bottle, so pretty crazy numbers there. And it’s easy to get down quickly. I fill my mouth with Gel Mix before the aid station, then swallow it with some water after. It’s a good way to get a lot of carbs in high density.”

Gustav’s race day fueling setup.

“No one goes training day in, day out just to tell a good story. You go day in, day out to really do the best you can. And the best anyone can do is to win. There's no question of who is the winner. You can question who has the best story, or who has the most fun, or question a lot of things, but it's never a question who is the winner.”

That winning mindset requires Gustav to consider all aspects of his setup. Because IRONMAN is not only competitive in terms of the number of competitors who could win — it’s the number of competitors who are fast from start to finish. “Every bottle you start with is weight. One bottle is one kilo, and it starts to add up. Kona is definitely not a flat race.”

Forecast matters, distance between aid stations matters, course profile matters, race intentions matter. It’s an equation that impacts fueling. “Normally I do a four-bottle setup. Two one-liter bottles with three Drink Mix 320s in each. The aero bottle with Gel Mix. And a frame bottle that starts at a super high concentration that I water it down as I go with fresh water from the aid stations.” It’s high-carb fueling that Gustav has practiced over years of training. Don’t copy it — fuel on your terms.

“I take 80 grams in T1. Then approximately 160 grams per hour on the bike, and a little lower on the run — around 100. We’ve been pushing up, up, up, at the same time as the power is going up and the pace is going up.”

Ultimately, there’s no point planning if you don’t execute the strategy in the race. This is what your body expects — physically and mentally.

“The most important thing with the plan is to follow it, and to be able to drink it all. If I hit my 160, I don’t think fueling will be a limitation for my end performance.”

The night before.

Remember, elite athletes often feel the same as you when it comes to the biggest races. Nerves can be a limitation of you let them control your actions. “Race morning I’m normally so nervous it’s hard to get much down. So, for me, fueling before means the evening before. A big dinner, maybe 90 percent rice and a little bit of chicken. Eat to fuel, not to feel good. Then some Drink Mix during the evening, and maybe some Haribo, just to relax.

And once Kona — the thing that influences most of his day-to-day process — is behind him, Gustav allows himself the luxury of relaxing.

“After a normal IRONMAN, I’m straight into the carbs. After Kona, I don’t even think about it. I know the job is done. There’s nothing more to do.”

Interview by Ross Lovell
Photographs by Love Ljungström