Fuel To Thrive | A Beginner’s Guide to Endurance Nutrition
If you're taking on any endurance challenge, one thing is certain - your body needs fuel, and lots of it. Whether out on the trails, sat in the saddle, walking an ultra or adding swimming in an Ironman, getting your fuelling right is the difference between thriving and surviving.
Running out of energy mid-event is the nightmare scenario no one wants to face. So, how do you keep your engine running smoothly over hours (or even days) of effort? The answer: carbohydrates.
Let’s break down everything you need to know about fuelling for an ultra-endurance race, from what to eat, when to eat it, and how to train your gut to handle it all.
Why Carbs Are King
Carbs are your body’s go-to fuel source during endurance exercise. While fats and proteins have their place, they just can’t provide energy as quickly as carbohydrates. The catch? Your body can only store a limited amount of glycogen (the stored form of carbs), which means regular fuelling is key to keeping your energy levels steady. While even the leanest of athletes have enough fat stores available to run for days, unfortunately, our carb stores aren't quite as plentiful.
How Much Carbs?
For ultra-endurance events, research suggests consuming 60-90 grams of carbohydrates per hour. Carb intake above 90 grams per hour is possible following a gut training program for experienced runners. Still, it is achievable for ultra cycling events where digestion is slightly easier than during high-impact running. A general rule of thumb is that the more carbohydrates you can consume, the better you perform... providing you can avoid any gastrointestinal issues.
The best source of carbohydrates!
It may seem obvious, but the best source of carbohydrates is the ones that work for you. Everyone is different, and what may work for one person may not work for you.
Try many different sources of carbs during your training, from an energy gel, all the way to a jam sandwich - find what suits you. Test all these sources to the max - across intense intervals, long rides, steep ascents and challenging descents, even in the heat. A fuelling diary is a great way to track what's working and help you select your carb sources for race day.
If you don't know where to start, we’ve put together a taster bundle to explore what may work for you.
● Energy gels (quickly absorbed but can be tough on the gut if not practiced)
● Sports drinks (carbs provide us with energy but also improve fluid absorption, helping us stay hydrated, but also providing a boost with every sip)
● Chews or gummies (sweets? yes please! Tasty, quick boost, but maybe difficult to chew if you're breathing hard)
● Bars (digested more slowly, offering a more sustained energy release)
“Loved the subtle flavour, not overly sweet like some gels, easy on the stomach and gave me a boost when I needed it. Gave me some confidence for completing my first half marathon”
● Real food (such as bananas, pastries, jam sandwiches, cookies, and doughnuts are great for longer events with rest stops)
Timing Your Carb Intake
Don't wait until you're hungry or feeling sluggish—by then, it's too late! Instead:
● Start fuelling within the first 30 minutes of your race.
● Distribute your carb intake across the hour
● Take in small amounts every 15-20 minutes rather than all at once.
What Else Do I Need To Know?
Flavour warning: Selecting a carb source like a gel can be a minefield. You can choose from an endless list of flavours, ranging from your favourite dessert, all the way to the exotic cocktail you had by the pool on your last holiday.
So, where to start? Trying a range of brands is really important, as they often have different textures and consistencies. Although a sweet, strong-flavoured gel may be delicious as a one-off, you will thank yourself for selecting a neutral-flavoured, more refreshing gel later on in the race. Mixing 101 different flavours isn't recommended unless you want to be burping up a cocktail of gels for the rest of the race.
Caffeine Awareness: Some carb sources contain caffeine to give you an added boost. Caffeine enhances performance in many ways, mainly by making things feel a bit easier (this is why coffee is so effective on a Monday morning at work!). On the flip side, caffeine can cause digestive issues, including the urge to quickly find the nearest loo! We recommend:
● Test caffeine during training to understand your body's response.
● Get used to taking carbs before adding caffeine into the mix. Caffeine is the bonus 5%, not the foundation of your fuelling.
● People who often use caffeine in their day-to-day lives find it easier to consume caffeine during exercise.
Carb maths: When you’re in the zone, focused on a technical climb, with only 12 miles to go, the last thing you want to be doing is trying to work out how many grams of carbs you’ve had. Do yourself a flavour (sorry, I couldn’t help myself), make your life easy when choosing your carbs. Using carb sources which have a round number of carbs (eg 30 grams), makes a world of difference when it comes to tracking your hourly carb target.
Pre-Race Fueling: Laying the Foundation
What you eat before race day is almost as important as what you consume during the race. Here’s how to prepare your body for optimal performance:
The Night Before:
● Prioritise easy-to-digest carbs like pasta, rice, or potatoes.
● Add a moderate amount of protein and some healthy fats
● Avoid meals which are really high in fat
● Keep fiber low to reduce any chance of GI distress.
Morning of the Race:
● Aim for a high-carb, low-fiber meal 3-4 hours before the start (e.g., oatmeal with honey, toast with jam, or a bagel with banana).
● Hydrate well, using electrolytes - we recommend PH1500 for electrolyte loading
● This should be tried and tested before every long run in your training - race morning is not the time to experiment!
One Hour Before:
● A small, fast-digesting carb source, such as an energy gel, chews or a banana.
● Sip on a sports drink to keep hydration levels up - PF30 Carb and Electrolyte drinks mix offers an energy boost and optimised hydration all in one.
Gut Training: Your Secret Weapon for Success
Your gut is just like any other muscle - it needs training. Taking in large amounts of carbs during a race can cause stomach distress if your digestive system isn’t used to it. That’s where gut training comes in.
Here’s how to prepare your stomach for race day:
Start gut training from week 1 of your training program.
Practice fueling at least once per week during long runs to simulate race-day conditions.
Practice fuelling at high and low intensities - we want to be comfortable taking on carbs when we are working hard and easy. When we are working hard and blood flow is being prioritised by our muscles, this is when are gut is being challenged most
Gradually increase the amount of carbs you consume each week—start at 30-40 grams per hour and build towards your race day target.
Train your gut to tolerate more than you’ll need on race day, so you have a buffer if things don’t go as planned.
Make adjustments before race day - experiment with different carb sources to find what works best for you.
“I’ve used these (TrailMed’s Fuelling Taster Bundle) for training, races, and recovery, and they’ve really proved to be a vital part of my performance.”
Considerations for Your Race Strategy
While 60-90g of carbs per hour is a solid guideline, there's a few more things to consider to help you get your fuelling right on race day:
1. Exercise Intensity
● Higher intensity = greater carb demand.
● Climbs and elevation will force an increase in intensity. Slowing down or walking is worth considering to preserve your glycogen
2. Event Duration
● Shorter ultra races (e.g., 50K) may allow for a slightly lower hourly carbohydrate target.
● Longer races (e.g., 100-mile ultramarathon, full Ironman) require aggressive fuelling from the start.
3. Environmental Factors
● Heat: Increases the rate at which we use our muscle glycogen stores. Racing in the heat warrants an increase of 10% compared to temperate environments
● Altitude (over 1500m): Forces us to use carbohydrates more readily. Increasing your hourly carbohydrate target by 10-20% may make all the difference. Altitude can also slow our digestion, so easy-to-digest carb sources may be the best option.
4. Race Logistics
● Plan fueling around aid station locations—carry extra fuel if aid stations are far apart.
● If your event has longer rest stops, consider consuming solid food to keep hunger at bay.
Time to ace your fuelling strategy!
Hopefully, you now feel more confident to fuel your next ultra. We understand that it can take 100s of miles to get your fuelling right, so we are keen to make things a little bit easier.
We've designed our Personalised Fuelling Plan to help you get your fuelling right when it really matters on race day.
Final Thoughts: Practice, Adjust, Execute
Fuelling for an ultra-endurance race is both a science and an art. While guidelines provide a great starting point, trial and error during training will help fine-tune your strategy. The more you practice, the better your body (and gut) will adapt, setting you up for success on race day.
So, start fuelling early, train your gut, and get ready to go the distance - without hitting the dreaded wall.
Happy fuelling!
