How Men and Women Fuel for IRONMAN
Differences AND similarities
People like to say that nutrition is the fourth discipline of triathlon.
What they mean is that it doesn’t matter how well you train your body for swim, bike, and run, if you neglect nutrition, you may find yourself visiting a port potty on the way to the finish line.
But nutrition can be soooo complicated.
There are some best practices, of course, but nutrition strategy is largely unique to each individual athlete.
For example, Matt and I are different in our approach to how we fuel triathlon- for 140.6 miles in particular. Part of it has to do with personal preferences, but also our different physiological needs.
Today, with some help from the sport scientists at Precision Fuel & Hydration (who have kindly lent me their database of athlete case studies), we’re going to look at how men and women fuel for an Ironman triathlon.
Read on to learn:
How men fuel for Ironman- the stats
How women fuel for Ironman- the stats
Biggest differences between male and female fueling strategies
A bit about Precision Fuel & Hydration
Precision Fuel & Hydration is the Official Hydration Partner for IRONMAN races in Europe, Australia, New Zealand, and South Africa in 2025.
*If you’re a US-based athlete, why does this mean anything to you? Well, PF&H is used by athletes all over the US, and they have sweat-testing centers in the states. Also, it’s the on-course nutrition at the 70.3 World Championship this weekend in New Zealand and the 2025 IRONMAN World Championship in France and 70.3 World Championship in Spain, so they’re good folks to know.
Yes, they sell nutrition products, but that’s not how the company got its start. After their founder struggled with cramping and other hydration-related issues, he used trial and error to develop his own plan, along with some help from patented sweat-testing technology.
Then, they developed a range of electrolyte supplements and started working with athletes in the NFL, NBA, MLB, and of course triathlon.
Their focus, first and foremost, is on sport science and athlete education, regardless of what nutrition brand you use.
They have a Knowledge Hub with helpful videos, but the coolest thing are their Case Studies. That’s what we’re looking at today. It’s a database with over 671 nutrition case studies from a wide range of sports, including running, cycling, and triathlon.
You can filter a search by gender, pro or age-group status, sweat concentration, weather, and distance to see how different athletes fuel their races.
You can see race plans for pro triathletes like Jason West, Tamara Jewett, Ellie Salthouse, and Leon Chevalier.
Caution: If you’re a triathlon data geek, you can spend hours here…
So without further adieu, let’s dive into the numbers!
*Keep in mind that when we look at averages, some detail can be lost. Also, we don’t have thousands of case studies to look at, but instead a select group with more pros being represented than age-groupers.
How Men Fuel for Ironman
Within the PF&H database, there are 67 Ironman-specific case studies that include 40 pros and 27 age-groupers.
Here’s the stats:
Finisher’s time: 6:42:31 (no swim) to 14:46:46
Average finisher’s time: 9:01:12
Average race temperature- 72°F degrees
Now, let’s look at some of the specific data.
87% of men had a final dose of carbs within 30 minutes prior to the race start. This is often done by taking an energy gel on the way to the swim start.
It’s a pretty common practice and something that both Matt and I do as well. In fact, 100% of athletes used energy gels as part of their nutrition strategy.
54% of men used caffeine in the final 30 minutes before the race start. Although Matt does have an energy drink about 2 hours before the race, he doesn’t take any additional caffeine before the swim start.
61% of men pre-loaded with a strong electrolyte drink. Matt does take a 10 oz. bottle with him to transition and sips on in throughout race morning. However, it’s a typical carb/electrolyte mix with 30g carbs and 200mg sodium, so not exactly a “strong electrolyte drink.”
78% of men hit the recommended 60-90+ grams of carbs per hour. The actual range was 53-130 g/h, and the average was 88 g/h.
Men tend to front-load their nutrition, meaning they take in more on the bike than they do on the run. This is because it’s often easier to consume carbs while riding a bike than while running. Also, as the day progresses, the risk of dehydration and potential stomach upset increases, so fueling early and often is a pretty standard policy.
Matt falls in this range at 70 g/h on the bike and about 60 g/h on the run.
Here’s what the average breakdown looks like:
All men- 108 g/h on bike, 75 g/h on run
Pros- 114 g/h on bike, 75 g/h on run
Age-groupers- 98 g/h on bike, 76 g/h on run
100% of men used energy gels during the race, but only 22% used chews. Spoiler alert: This is different for women…
64% of men hit their recommended targets for fluid and sodium. While fluid intake depends widely on weather conditions, the range was from 9 oz/h to 60 oz/h with an average of 25 oz/h in hot races. Matt’s right in this range at about 22-26 oz. per hour.
Men consumed an average of 964 milligrams of sodium per liter of fluid. Matt takes in between 600-800 milligrams of sodium per liter of fluid.
How Women Fuel for Ironman
Now, it’s time for the ladies!
Within the PF&H database, there are 55 Ironman-specific case studies consisting of 40 pros and 15 age-groupers.
Here’s some stats:
Finisher’s time: 7:59:57-13:00:57
Average finisher’s time: 9:23:42
Average race temperature: 74°F degrees
Now, for some specifics.
93% of women had a final dose of carbs less than 30 minutes before the swim. This is me! I have a gel about 15 minutes before the race starts.
51% of women used caffeine less than 30 minutes before the race. This is not me! I’m pretty sensitive to caffeine, because I don’t drink it in my everyday life, so I rarely consume caffeine on race day.
Only 55% of women hit the carb amount recommended (60-90+ g/h). The data also suggests that many female age-groupers aren’t meeting fueling needs, as compared to pro women and men.
The carb intake range for women was 37-109 g/h and the average was 77 g/h.
Women also tend to front-load nutrition on the bike. Another interesting point is that pros had higher numbers than age-groupers on the run.
All women- Bike- 88 g/hg, Run- 74 g/h
Pros- Bike- Bike- 90 g/h, Run- 78 g/h
Age-groupers- Bike- 84 g/h, Run- 61 g/h
100% of women used energy gels during the race. While I use a few energy gels on the bike (and carry some on the run) I may or may not use them depending on how I’m feeling, since I carry my own carb mix for the marathon.
98% of women pre-loaded with a strong electrolyte drink on race morning. I’m like Matt in that I drink 15 oz. with 30 g of carbs and 200 mg sodium in transition.
62% of women hit their recommended targets for fluid and sodium intake. We know that fluid intake varies based on race conditions, but the average was 737 ml of fluid per hour in hot races.
As you might expect, when races were categorized into mild, hot, and very hot, the average fluid intake increased with hotter temperatures.
Mild- 638 ml/h, Hot- 666 ml/h, Very hot- 816 ml/h
Women consumed an average of 856 milligrams of sodium per liter. I’m within this range at about 600-800 milligrams of sodium per liter.
Although there aren’t as many case studies for women as there are for men, the PF&H sport scientists are working to expand their female case studies to include more stats from the recent Ironman World Championship in Nice!
Differences between male and female Ironman fueling strategy
After looking at the data, we can see that there are a few differences in how men and women fuel for Ironman.
The biggest different is carb intake on the bike. Men averaged 108 g/h, while women averaged 88 g/h.
Another difference is the carb decrease from bike to run. Both pro and age group men take in almost the same amount on the run- 75 and 76 g/h, respectively. But pro women take in 17 more grams of carbs per hour on the run than their age-group counterparts.
While 78% of men hit the recommended carb target (60-90+ g/h), only 55% of women fell in the prescribed range, raising concerns about potential under-fueling among female athletes.
Another big difference is that almost all of the women (98%) pre-loaded with a strong electrolyte drink, as opposed to 61% of men.
While all athletes used a variety of different carb sources, there was one main difference.
Men- 46% drink mix, 100% gels, 22% chews, 12% bars
Female- 58% drink mix, 100% gels, 46% chews, 9% bars
*Women were more likely to use chews than men.
Despite these differences, there are actually more similarities in the way that men and women fuel for an Ironman.
Average carbs per hour isn’t that far off, with men at 88 g/h and women at 77 g/h.
Also, carbs taken in on the run was almost identical- 75 g/h for all men and 74 g/h for all women (although age-group women were on the lower end).
Sodium concentration wasn’t too far off, with men at 964 milligrams of sodium per liter and women at 856 milligrams of sodium per liter.
87% of men and 93% of women both took final carbs in the 30 min. before the race. 54% of men and 51% of women both used caffeine in those final 30 min.
64% of men and 62% of women hit their recommended fluid and sodium targets. 100% of athletes used gels, and both genders front-loaded nutrition.
With all this talk about nutrition, there’s something we haven’t discussed that’s an integral difference between men and women… menstrual cycle.
It’s a multi-faceted topic, and one that deserves its own post, so I’ll direct you to this great one- Do women have different hydration needs than men?
But here’s my favorite quote.
“While suggestions have been made that physiological differences between men and women will mean our approaches to hydration should differ, my interpretation of the evidence is that viewing hydration on an individual scale and accounting for a person’s size, sweat rate and sweat composition, their sport and their environment, is of far more importance than their sex.”
- Abby Coleman, Sport Scientist
When talking about fueling for triathlon, especially long-course races like Ironman, one size doesn’t fit all.
There are some best practices, sure, but ultimately your nutrition strategy has to work for YOU. That’s why I always recommend getting guidance from a nutritionist, coach, or sport scientist to set yourself up for success.
You can fake it until you make it in short course, and maybe even a 70.3. But an Ironman is a whole different best entirely…
In the meantime, if you aren’t subscribed to the PF&H newsletter, I would highly recommend it. It’s informative with a quirky sense of humor.
One of the PF&H sport scientists will be a guest on an upcoming Zoom talk for the Triple Threat Life Club in early 2025, so if you’re not a member of the Club, join today!
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New & Notes
Join us in wishing good luck to our friends and subscribers racing this weekend! Good luck to Noah, Sebastian, and Emily racing their first half-ironman at 70.3 Florida, as well as Lisa, Lucas, Ciara, Alia, and Bella at the 70.3 World Championships!
I had so much fun talking with Justin Waller on the Money Mile podcast.
Justin is a 6 x Ironman and finance expert who founded Waller Financial Coaching to ensure active people are as prepared for the future as they are for race day.
He even has a free e-book: Financial Independence for Triathletes.
On the podcast, we talk about:
- How I got started in triathlon
- The best investment I’ve made in my athletic career.
- How we use Triple Threat Life to share practical knowledge, expert insights, and mindset skills with athletes.
Click here to listen to episode 66 on the Money Mile podcast.
My third Race Guide is live for Triathlete Magazine! This one focuses on the Best Sprint and Olympic Distance Triathlons in the US for 2025.
Thanks to each and every one of you for subscribing to the newsletter and for taking the time to read my words. My goal, first and foremost, is to help people, and the best way I can do that is through my writing.
See you next week!