Fuel the Story: Jen Done on completing back-to-back Ironman triathlons within 48 hours
This is Fuel the Story — a series of real conversations with runners and triathletes about how their nutrition has evolved.
Not one of them nailed it from day one. Every one of them is still learning, still evolving their approach and still getting things wrong sometimes. Because nutrition isn’t something you just look at once and forget about — it changes as your training, goals, life and experience change. We’ll talk about what’s worked, what hasn’t and what they’ve learned along the way, because your nutrition doesn't need to be perfect to make a difference to your performance — it just needs to keep improving.
Jen Done is a triathlete, triathlon coach and host of the Toughest Finish Line podcast. In August 2026 she did something most people would consider impossible: two full Ironman triathlons on consecutive days — Ironman Kalmar on Saturday, Ironman Copenhagen on Sunday — travelling between them overnight by van. She raised money for the Ironman Foundation along the way.
I wanted to talk to Jen for Fuel the Story because her experience demonstrates something I talk about constantly: having a plan is not the same as being able to execute it. And the ability to adapt when things go wrong — not panic, not abandon the whole thing, just adapt — is as important as the plan itself.
What is a back-to-back Ironman?
A single Ironman triathlon is a 2.4-mile open water swim, followed by 112 miles on the bike, then a full marathon. Jen completed two of these, on consecutive days travelling between them overnight by van.
Within 48 hours Jen covered more than 280 miles under her own steam, and her second race was only four per cent slower than her first.
How Jen got into triathlon
Jen found triathlon when she was suffering from postnatal depression. She had never ridden a road bike and had barely swum when her husband encouraged her back to running after the birth of their daughter.
"I couldn't even get out the front door. The anxiety was just stopping me. I managed a 30-second run and built it up from there. It wasn't the cure, but I felt so much better each time. I could just clear my head."
From that 30-second run, she progressed to a 70.3 (or half Ironman), then a full Ironman. She was then lucky enough to go to the Ironman World Championships as part of a group of women sharing their stories supported by the Ironman Foundation.
How her nutrition has evolved
Jen did her first full Ironman in 2022 and I'm sure her description of her nutrition at the time will be familiar to lots of you.
"I had no idea. I'd used gels when I'd done marathons, but eating on a bike when you're trying to balance and you're feeling unsteady — that was very new. At the time it was whatever was easiest that I could get open and get down."
Traditionally, Jen has used real food on the bike as a break from the sweet, gloopy gels. However, for the back-to-back attempt she decided to move away from real foods on the bike — ditching brioche rolls and malt loaf and moving to a carbohydrate drink mix for the first time in a race to help with the logistical challenges of the two races.
This isn't something she did on a whim. She practiced it in training and set her targets at 80-90g of carbohydrates per hour for the race. And her plan was right in line with current guidance on carbohydrate intake for an Ironman, which you can read more about here.
Race week and carbohydrate loading
Although Jen doesn't track her numbers when she is carb-loading, she consistently adds carbohydrates to her meals particularly in the last few days before the race to make sure that she has enough energy in the tank.
One of the downsides to carb-loading is feeling a bit heavier in the few days before the race. This is because for each gram of glycogen (or carbohydrate) that the body stores, it also stores about 3g of water. But for Jen this is a small price to pay.
"For a race like Ironman — let alone a back-to-back — it's essential. You're already at a disadvantage on the start line if you haven't got that right."
Day one: Ironman Kalmar
Jen had a nutrition plan. Then the airline lost her luggage, which contained almost all of her nutrition and it was a stressful start to the challenge.
"I had about 20 minutes before my registration closed. I was just shoving things in. I didn't have time to work it all out."
Despite the chaos, she stuck broadly to her plan — 80–90g of carbohydrate per hour from a mix of gels, carbohydrate drink and Haribo. But towards the end of the marathon she started to feel nauseous.
The nausea wasn't something new for Jen - and is something lots of endurance athletes struggle with. There are lots of reasons for nausea - your body diverts blood away from your gut to support your working muscles, the nutrition plan you have worked on so hard in training might not work if you're working harder on race day, the weather conditions can have an impact and simply relying on lots of sugar.
Between the races: the part where the plan started to fall apart
After crossing the Kalmar finish line, Jen had four hours in a van to Copenhagen and four and a half hours of sleep before race two. This window — the recovery between the two races — is one of the most nutritionally critical part of the whole challenge. And it's where things fell apart.
"My husband had bought me my favourite chocolate bar. I took one bite and I couldn't eat it. I had pasta ready to go. It was one mouthful at a time. I managed to get a protein bar and a protein shake down, which I was pleased with. But I didn't eat as much as I'd planned."
Eventually she prioritised sleep over food. Given the circumstances, that was probably the right call. But it meant she started race two in a significant energy deficit on top of the one she'd already accumulated from the day before.
Day two: Ironman Copenhagen
Unfortunately, Jen was still feeling sick when she woke up on day two and managed less than half a bagel, no peanut butter, before the swim start. Things didn't improve out on the course. Her carbohydrate intake dropped from the planned 80–90g per hour to no more than 30g.
"I knew it was a worry. I didn't know if I was going to have enough energy to get around."
Three things got her to the finish line:
Carbohydrate drink mix on the bike. Slowly, inconsistently, but something rather than nothing. Liquid carbohydrate empties from the stomach faster than solid food at race intensity so keeping it going, even in small amounts, was the right instinct.
Coke on the run. Like lots of endurance athletes, Jen doesn't drink Coke as a rule, but it's something that really works on race day. Although lots of people think it's the sugar that gives them a boost, it's more likely to be the caffeine doing the work. I've written more on caffeine and endurance performance here.
A mint humbug from her mum. "It was the best thing. It helped the nausea. It didn't make it go away but it helped an awful lot." There is evidence that peppermint and menthol can help reduce nausea — worth knowing if you struggle with nausea in long events. Ginger has stronger evidence, so is a good alternative.
What she's still working on
Jen is candid that she will be reviewing her nutrition again.
"There were elements that worked and absolutely elements that didn't. I need to go back to the drawing board."
Her biggest takeaway from the whole experience is the need for flexibility — something she now talks about with the athletes she coaches. Always have a plan. But be prepared to adapt and don't panic. Laura Watts talked about this too in the first episode of Fuel the Story: she has a plan A, B and C, and then eats whatever she can get down.
And Jen's advice to her younger self — the one who barely fuelled her first marathon?
"Make sure you do fuel. If it's hot, you need to change your plan. Just pay attention to your body and plan for it where you can."
What's next for Jen
Jen is taking some time before committing to what comes next — which, after back-to-back Ironmans, seems entirely reasonable!
You can follow her on Instagram at @iron_woman_triathlon and listen to her podcast, The Toughest Finish Line, wherever you get your podcasts.
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If Jen's story has you thinking about your own long-course race nutrition, this is exactly the sort of thing we work through together in a 1:1 consultation — building a strategy around your training, your race, and what actually works for you. |
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