What to Eat During an Ultramarathon: Fuelling Strategies for Every Distance
Fuel is everything in an ultramarathon. Whether you’re racing 50K or 100 miles, what you eat can make or break your day. And unlike shorter races, you can’t just rely on a few gels and some Gatorade—you need a real nutrition plan that supports hours (or days) of effort, keeps your stomach happy, and helps you stay strong to the finish.
In this guide, we’ll break down how much and what to eat during an ultramarathon, how to avoid stomach issues, and tips for fuelling smart across different distances.
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Why Nutrition Matters in Ultras
Ultramarathons are endurance puzzles—and nutrition is one of the biggest pieces. You’ll be burning thousands of calories, depleting glycogen, sweating out electrolytes, and flirting with dehydration or GI distress if you’re not careful.
Good nutrition helps you:
- Maintain steady energy and mental clarity
- Avoid bonking or sudden crashes
- Prevent cramps, nausea, or stomach shutdown
- Recover faster after the race
And even if you’re blessed with an iron stomach like I usually am, you’re still not immune to fuelling challenges. During long races, I’m always surprised by how unappealing my go-to foods suddenly become—and how hard it is to get enough carbs down.
Plus, as a particularly salty sweater, I’ve also learned (the hard way) that falling behind on electrolytes doesn’t just lead to cramping or fatigue. For me, it shows up as blurred vision—an extremely frustrating side effect of dehydration and sodium imbalance. And, once it kicks in, it tends to stick around for the rest of the race. Trust me: navigating technical trails in the dark with limited eyesight adds an entirely new level of difficulty!
Nutrition doesn’t just support performance—it affects every part of your ultra experience, including how much you enjoy the day. As outlined in the International Society of Sports Nutrition’s position stand, proper fuelling plays a key role in performance, recovery, and overall health for ultra-distance athletes—so it deserves to be a major focus in your race planning.
What to Eat During an Ultramarathon
How Much to Eat
There’s no one-size-fits-all, but here are the general guidelines most experts recommend for ultramarathon fuelling:
| Nutrient | Per Hour Target |
|---|---|
| Carbohydrates | 60–90g per hour (depending on effort & duration) |
| Fluids | 400–800 ml per hour (adjust based on sweat rate & weather) |
| Sodium (Electrolytes) | 300–1000+mg per hour (highly individual—see note below) |
For shorter ultras like a 50K (or any event under 8 hours), aim for at least 60 grams of carbs per hour. In longer races (50 miles, 100K, or 100+ miles) you’ll want to train your gut to handle higher intakes—ideally 60 to 90+ grams per hour. The longer you’re out there, the more important it becomes to stay consistent with fuelling and to practice this intake in training.
It’s also important to start your race with full glycogen stores. In the days leading up to your ultra, gradually increasing your carbohydrate intake—also known as carbo-loading—can help you avoid starting in a depleted state. I learned this lesson the hard way during one of my first races, when due to illness, I barely ate during race week and then overdid it the day before—definitely not the ideal strategy.
Fat & Protein: These aren’t essential in shorter races but can play a role in longer events (12+ hours). Fat provides a slower-burning fuel source, especially on lower-intensity sections, while protein can help reduce muscle breakdown over time. Although these are best consumed as part of other foods—like bars, nut butter, wraps, or broth—in longer ultras, when glycogen stores begin to drop, the body relies more on fat as a secondary fuel source—particularly at lower intensities.
Note on Sodium: Electrolyte needs vary significantly between individuals. If you’re a heavy or salty sweater (like me), it’s worth getting a sweat test to determine your sodium loss rate. This allows you to better match your intake during training and racing—something I’m still working on, after a few blurry-vision episodes caused by underestimating my own needs.
Best Foods for Ultramarathons
The best foods for ultramarathons are highly individual—the ones that work are the ones you’ve trained with and can digest while running. That said, even if you’ve practiced with a particular fuel, you may find it doesn’t sit as well on race day. Your appetite and tolerance can shift under race-day stress, heat, or fatigue.
To give yourself the best shot at success, practice your fuelling strategy during long training runs and race simulations—ideally using the same timing, pace, and terrain as your target event.
That said, here’s a mix of go-to options that tend to work well for most ultra runners. They’re high in carbs, easy to digest, and versatile across distances:
Quick-Digest Carbs (Great for any ultra)
These fast-acting carb sources are easy to carry and tend to work well across most ultra distances:
- Energy gels (Maurten, SIS, Honey Stinger, GU, etc.)
- Chews or gummies (like CLIF Bloks or candy such as gummy bears)
- Sports drinks (Tailwind, Skratch, Precision Fuel & Hydration)
- Cola or ginger ale (typically available at aid stations)
- Maple syrup or honey (e.g., Brix or Sun River energy gels—or bring some in a soft flask)
Real Food (Especially for longer efforts)
In races lasting 8+ hours, most runners will crave “real” food in addition to gels and drinks. These are common go-tos:
- Bananas, oranges, watermelon
- Boiled potatoes with salt
- Mashed potato or sweet potato
- PB&J sandwiches
- Cookies (Oreos are a classic aid station favourite)
- Candy (gummy bears, M&Ms, etc.)
- Pretzels, chips, crackers
- Trail mix, granola bars or flapjacks
- Pickles (and even pickle juice)
These types of foods are often available at aid stations. But if there’s something specific you rely on, bring it with you! Pack some on you, and stash extra portions in your drop bags just in case.
Pro tip: For liquids or purees like mashed potato, use small soft flasks or reusable baby food pouches to make them easier to carry and eat on the move.
Longer Ultra Fuel
In longer events (especially 100 milers or 200s), hot food becomes a key part of staying fuelled and grounded. Aid stations may offer:
- Soup or broth
- Noodle cups (like instant ramen)
- Sandwiches or wraps
- Quesadillas or grilled cheese
- Pizza rolls
- Rice balls
- Pierogies
- Pasta
- French fries
- Liquid calories (smoothies, protein or recovery shakes)
And in multi-day events like 200 milers, some aid stations even take hot food orders—think bacon and eggs, pancakes, or a burger. At that point, you’re fuelling a small expedition!
Common Fuelling Mistakes
Even experienced ultra runners make fuelling mistakes from time to time—and they can derail your race fast. Here are some of the most common errors to watch out for (and how to avoid them):
Going too long without calories
In an ultra, your energy demands are constant—and waiting until you feel hungry is usually too late. Even if you don’t feel like eating, you still need to take in calories regularly. Aim to consume something every 15–30 minutes, whether it’s a sip of drink mix, a bite of a bar, or a gel. Set a timer if you tend to forget.
I always find it harder to eat during races than training—even my favourite foods can suddenly become unappealing. But I’ve learned that it’s important to treat fuelling like a discipline: eat early, eat often, and be consistent.
Trying something new on race day
One of the golden rules of endurance sports is nothing new on race day. Unfamiliar foods and drinks are a top cause of GI distress. Stick to what you’ve trained with, and if you’re relying on aid stations, do your research ahead of time to know what will be available—and test similar items in advance.
Relying only on sweet food
A common mistake, especially for newer ultra runners is to rely too much on sweets. Sweet gels and chews may work well early on, but after 6+ hours you’ll likely start to get serious flavour fatigue and they may no longer go down well. Mixing in savoury options like pretzels, chips, broth, or potatoes can help reset your taste buds and keep you eating throughout the race.
Overfuelling or eating too much, too soon
It’s tempting to chow down at the first few aid stations or to front-load calories, especially if you’re feeling good. But overfuelling—especially early—can backfire. Too much food in a short time can lead to bloating, nausea, or an upset stomach. Spread your intake out and stick to small, consistent portions.
Ignoring electrolytes
Carbs and fluids get a lot of attention—but don’t overlook electrolytes. If you’re a salty sweater (like me), underestimating your sodium needs can result in cramps, dizziness, or in my case, blurred vision – not to mention it can be really dangerous for your health. Whether you use salt tabs, chews, or drink mix, electrolytes are critical—especially in hot or humid conditions.
Not adapting mid-race
Even with a perfect plan, things can change on race day. What worked in training might not sit well after 8 hours of running. The key is being flexible—bring backup fuel options, adjust your intake based on how you feel, and don’t be afraid to switch things up if needed.
How to Build a Nutrition Plan
A solid fuelling plan is just as important as your training plan. It keeps you moving, prevents energy dips, and helps avoid stomach issues that could force you to slow down—or stop entirely. But building a plan that works is highly individual and requires some trial and error.
Here’s how to structure your nutrition strategy:
1. Know Your Hourly Targets
Start by calculating your approximate needs:
- Carbs: 60–90g per hour
- Fluids: 400–800 ml per hour (adjust for sweat rate and weather)
- Sodium: 300–1000+ mg per hour (individual—consider a sweat test)
Use these numbers as your baseline, and adjust based on the race duration, terrain, and expected intensity. For example, I aim for a minimum of 60g carbs/hour but have been working to push this higher during training.
2. Choose Your Fuel Types
Select a mix of options that work for you—ideally combining:
- Quick carbs (gels, chews, drink mix, etc.)
- Real food (bars, fruit, pretzels, etc.)
- Electrolytes (salt tabs or chews, drink mix, salty foods)
Practice with them during long training runs to train your gut, dial in timing, and figure out what sits best.
I’ve found that liquid calories (like Tailwind or Skratch) go down easier when I don’t feel like eating—while small snacks and aid station treats add much-needed variety.
3. Practice With Purpose
Use long runs and back-to-back sessions to simulate race conditions. Follow your fuelling schedule, carry your race-day gear, and take in calories every 15–30 minutes.
Don’t just test foods—test timing, textures, portability, and flavour fatigue. I’ve had snacks I loved in training that suddenly became impossible to swallow mid-race.
4. Plan for Aid Stations
Know what’s available on course—but don’t rely on it blindly. Aid stations can run out of popular items, or your stomach might not agree with what’s there. Bring what you need to get between checkpoints and stash extras in your drop bags.
5. Pack a Backup
Always have a few emergency options. If your main fuel source starts making you gag, you’ll be glad you packed a gel you haven’t used yet or some candy to shake things up.
Fuelling by Distance
50K (4–8 hours):
- Gels, chews, drink mix, and simple snacks often suffice
- Start fuelling early—within the first 30 minutes
- Aim for at least 60g carbs/hour
- Focus on hydration and electrolytes, especially in heat
50 Miles / 100K (8–18 hours):
- Combine quick carbs with real food (bars, fruit, potatoes, etc.)
- Plan to eat during slower, runnable sections
- Prioritize electrolytes—your hydration strategy will make or break you
- Gut training becomes even more important at this duration
100 Miles+ (24–36+ hours):
- Eat early and often—real food becomes essential
- Include protein and fat overnight to reduce muscle breakdown
- Plan “anchor meals” at key aid stations (noodles, broth, wraps, etc.)
- Expect your food preferences to change—be ready to pivot
Final Tips for Race Day
- Start fuelling early — don’t wait until you’re hungry
- Eat small amounts often — aim for something every 15–30 minutes
- Adapt to conditions — heat = more fluids and electrolytes, cold = more calories
- Listen to your stomach — but don’t panic if things feel off temporarily
- Practice everything in training — fuel, pace, terrain, gear, and mindset
Ultramarathon fuelling is part science, part art. The right food can keep you steady, focused, and moving strong—while the wrong one can derail your day fast. Even with a great plan, things might go sideways. That’s okay. Be ready to adapt, listen to your body, and troubleshoot on the go.
Start small, test often, and figure out what works for your gut, your goals, and your race. Your stomach might not always love ultrarunning—but with the right prep, it doesn’t have to stand in your way.
What’s your go-to fuel for race day? Let me know in the comments—I’m always looking for new snacks to try on the trails!
