This ultramarathon nutrition guide explains how to plan your fueling before, during, and after a long trail race. You’ll learn how to think about carbs, fluids, sodium, timing, and race-day execution without turning your plan into something complicated.
In a short race, a small fueling mistake might cost you a few minutes. In an ultra, a nutrition mistake can change the entire day. If you stop eating early, drink too much, forget sodium, or try new foods on race day, your legs might not be the real limiter. Your stomach might be.
This ultramarathon nutrition guide will help you understand what to eat before and during an ultramarathon, how many carbs per hour to target, how to think about hydration and sodium, and how to train your gut before race day.
The goal is simple: arrive at the start line with a plan you have already practiced.
Quick answer: what should you eat during an ultramarathon?
During an ultramarathon, most runners should eat small amounts early and often. The best foods are simple, familiar, and easy to digest while moving.
Common ultra fuel options include:
- Gels
- Chews
- Sports drink or carbohydrate drink mix
- Bananas
- Potatoes with salt
- Rice balls
- Bars
- Pretzels
- Broth
- Soup
- Fruit
- Simple sandwiches or wraps
- Other aid-station foods you have tested in training
There is no universal best food. The best ultra fuel is the one your stomach accepts at race effort, in race conditions, for the number of hours you expect to be out there.
If you are training for your first 50k, start simple. If you are training for a 100-mile race, you need more variety and more backup options because your taste and stomach may change during the race.
The four jobs of an ultramarathon nutrition plan
Your race nutrition plan has four main jobs:
- Provide enough energy to keep moving.
- Provide enough carbohydrate to support the intensity of the effort.
- Manage fluid and sodium so you can keep absorbing what you eat and drink.
- Reduce the risk of stomach problems by using foods you have practiced.
Most runners think about the first job only: calories. But calories are not enough by themselves. If the fuel is hard to digest, badly timed, too concentrated, or mismatched to the weather, it can still fail.
That is why your plan should include:
- What you will eat
- How much you will eat per hour
- When you will start eating
- What you will drink
- How you will handle sodium
- What you will do if your stomach turns
- What aid-station foods you will use
- What backup foods you will carry
How many carbs per hour for an ultramarathon?
A practical starting range for many long endurance efforts is about 30 to 60 grams of carbohydrate per hour. Some experienced athletes train their gut to handle more, especially in long races where carbohydrate availability can become a limiter.
But the right target depends on:
- Race duration
- Intensity
- Body size
- Heat
- Altitude
- Terrain
- Aid-station spacing
- Gut tolerance
- Whether you are using gels, drink mix, solid foods, or a mix
For a first 50k, you might start around the lower to middle end of the range and learn what your stomach tolerates. For a 100k or 100-mile race, you may need a more detailed plan with multiple fuel types and backup options.
Do not make race day the first time you try your target intake. Train your gut the same way you train your legs.
Calories per hour vs carbs per hour
Calories and carbohydrates are related, but they are not the same planning tool.
Calories tell you how much energy you are taking in. Carbohydrates tell you how much quick, usable fuel you are providing for running intensity. During an ultra, both matter.
For example:
- A gel might provide around 20 to 25 grams of carbohydrate.
- A serving of drink mix might provide 20 to 40 grams, depending on concentration.
- Potatoes provide carbohydrate but may require more chewing and digestion.
- Nut butter is calorie dense but high in fat, which can be slower to digest while running.
- Broth may help with fluid and sodium but usually does not provide much carbohydrate.
A good ultra plan usually combines fuel types. Sweet fuel is efficient, but many runners need savory options later in the race. Solid food can help psychologically, but too much fat, fiber, or protein can slow digestion.
What to eat before an ultramarathon
Your pre-race nutrition should be boring. Race week is not the time to experiment.
In the final 24 to 48 hours, many runners do best with familiar, carbohydrate-forward meals that are easy to digest. This does not mean overeating. It means avoiding unnecessary risk: heavy meals, very spicy foods, unfamiliar supplements, or large amounts of fiber if your stomach is sensitive.
The night before an ultra, common options include:
- Rice with a simple protein
- Pasta with a familiar sauce
- Potatoes and eggs
- Oats or cereal if that works for you
- Bread, soup, or simple foods you already tolerate
Race morning breakfast should also be familiar. Many runners eat two to four hours before the start, depending on start time and stomach tolerance.
Common pre-race breakfast options include:
- Oatmeal with banana
- Toast with honey or jam
- Rice or rice cakes
- Bagel
- Banana and sports drink
- Simple cereal
- Coffee only if you already use it before long runs
If your race starts very early, plan this in advance. Waking up and forcing down a huge breakfast at 3:30 a.m. is not a strategy. Practice early long-run breakfasts before race day.
When to start eating during an ultra
Start earlier than you think.
Many runners wait until they feel hungry. That is usually too late. By the time you feel a strong need for fuel in an ultra, you may already be behind.
A simple rule: start fueling in the first 30 to 45 minutes, then keep the rhythm steady.
That might mean:
- A gel every 30 to 40 minutes
- Sips of carbohydrate drink every 10 to 15 minutes
- A small bite of solid food at each aid station
- A planned mix of drink, gels, and real food by hour
The exact strategy depends on your race, but the habit matters: eat before the problem starts.
Hydration: how much should you drink?
There is no single fluid target that works for every runner.
Fluid needs depend on:
- Sweat rate
- Temperature
- Humidity
- Altitude
- Pace
- Body size
- Clothing
- Pack weight
- Aid-station spacing
The goal is not to drink as much as possible. Overdrinking can be dangerous, especially during long races. The goal is to drink enough to support performance and absorption without forcing fluid beyond what your body can handle.
Use long runs to learn your range. Notice how much you drink per hour in cool weather, then compare that with hot days. If you are racing in summer or on an exposed course, connect this with your heat training and race plan.
Sodium and electrolytes
Sodium matters because long races combine sweat loss, fluid intake, and hours of repeated fueling. But sodium needs vary a lot between runners.
Some runners lose a lot of salt in sweat. Others do not. Some tolerate electrolyte drink well. Others prefer capsules, salty foods, broth, or a mix.
Possible sodium sources include:
- Electrolyte drink
- Sodium capsules
- Broth
- Salted potatoes
- Pretzels
- Pickles or salty aid-station foods
Practice this in training. Do not wait until race day to discover that a specific capsule upsets your stomach or that your favorite drink mix tastes awful after six hours.
Aid-station strategy
Aid stations are useful, but they can also break your rhythm.
Before race day, check:
- How far apart the aid stations are
- Whether the race lists exact foods and drinks
- Whether there are water-only stops
- Whether crew access is allowed
- Whether drop bags are allowed
- Whether the race is likely to run out of certain foods late in the event
Then decide what you will carry and what you will rely on.
For a 50k, you might be able to carry most of your fuel. For a 100-mile race, you need a system: vest, crew, drop bags, aid-station foods, and backup options.
Do not assume every aid station will have what you want. Build your plan around what you control.
How to avoid stomach problems
Stomach problems are common in ultramarathons, but many are preventable.
Common causes include:
- Eating too much at once
- Waiting too long to start fueling
- Drinking overly concentrated mixes
- Trying new foods on race day
- Too much fat, fiber, or protein while running hard
- Heat stress
- Dehydration
- Overdrinking
- Starting too fast
To reduce the risk:
- Practice fueling during long runs.
- Start eating early.
- Use small, regular doses.
- Keep your effort controlled early.
- Test sweet and savory options.
- Practice in similar weather when possible.
- Keep backup foods in your vest or drop bag.
Your gut is trainable. If you never fuel your long runs, your stomach will not magically cooperate on race day.
Use Vert’s Nutrition Planner to create the first version of that plan, then adjust based on training.
Fueling by race distance
50k nutrition
A 50k is long enough that nutrition matters, but short enough that you can keep the plan simple.
Start with:
- A familiar breakfast
- Fuel within the first 30 to 45 minutes
- A repeatable carb target
- Fluids based on weather
- Simple backup food
If this is your first ultra, connect your nutrition practice with your 50k training plan. Every long run is a chance to test the plan.
100k nutrition
A 100k usually requires more variety. You may be racing through different temperatures, terrain, and appetite phases.
Plan:
- Carbs per hour
- Fluid per hour range
- Sodium strategy
- Aid-station plan
- Savory backup foods
- Caffeine timing, if used
- What you will do when your stomach feels off
If you are building toward this distance, pair your fueling practice with Vert’s 100k training plan.
100-mile nutrition
A 100-mile nutrition plan needs redundancy. You need a plan, and then you need a plan for when that plan becomes hard to follow.
Think in phases:
- Early race: stay calm and start fueling early
- Mid-race: keep intake steady and avoid big swings
- Night: use familiar foods, caffeine if practiced, and warm options if needed
- Late race: simplify decisions and keep eating small amounts
For this distance, read the 100-mile training guide and build nutrition into every long run and back-to-back weekend.
What about keto or low-carb ultra fueling?
Some ultra runners prefer low-carb or keto-style eating. That can work for some athletes, especially during easy aerobic training, but it does not remove the need for a race nutrition plan.
Even keto-adapted runners need to think about:
- Calories
- Fluids
- Sodium
- Gut tolerance
- Backup foods
- Whether race intensity will require carbohydrate
If you are exploring low-carb fueling, read Vert’s keto diet for runners guide. For most runners, the practical question is not whether keto is good or bad. It is whether the strategy supports the race you are training for.
How to use this ultramarathon nutrition guide before your next long run
The best time to build your nutrition plan is not the night before the race. It is before the long runs that teach you what works.
Before your next key long run, write down:
- Planned run duration
- Expected terrain
- Weather
- Fuel target
- Fluid target
- Sodium plan
- Backup food
- What you will change if your stomach feels off
Then test it.
After the run, write down:
- What you ate
- What you drank
- How your stomach felt
- Energy highs and lows
- Whether you wanted sweet or savory food
- What you would change next time
Use Vert’s Nutrition Planner to create the first version of that plan, then adjust based on training.
Final take
This ultramarathon nutrition guide is not about copying another runner’s exact plan. It is about building a system that works for your race, your stomach, your pace, and your conditions.
Start simple. Eat early. Practice often. Build backup options. Adjust for heat. Do not try new foods on race day.
The best nutrition plan is the one you can actually follow when the race gets hard.
FAQ
What should I eat during an ultramarathon?
Most ultrarunners do best with simple, practiced foods that provide regular calories and carbohydrates, such as gels, chews, drink mix, fruit, potatoes, rice balls, bars, broth, or other aid-station foods they tolerate. The best choice is the food you have tested during long runs, not something new on race day.
How many carbs per hour do you need for an ultramarathon?
A common starting range for long endurance events is about 30 to 60 grams of carbohydrate per hour, with some experienced athletes training their gut to handle more. The right amount depends on race duration, intensity, body size, heat, terrain, and gut tolerance.
How much should I drink during an ultramarathon?
Fluid needs vary by sweat rate, temperature, altitude, effort, and body size. Use long runs to learn your normal drinking range. The goal is to avoid both underdrinking and overdrinking, especially in long races where sodium balance matters.
What should I eat before an ultramarathon?
Before an ultramarathon, choose familiar foods that are easy to digest. Many runners use a carbohydrate-focused meal the night before and a simple breakfast two to four hours before the start, such as oats, toast, rice, banana, or another food they have tested in training.
How do I avoid stomach problems during an ultra?
Practice your race fueling in long runs, start eating early, use foods you tolerate, avoid large single doses of calories, adjust intake in heat, and build backup options for when sweet foods stop sounding good. Gut training is part of ultra training.
How do I use this ultramarathon nutrition guide to build a race plan?
Start with your race distance, expected finish time, aid-station spacing, weather, terrain, and known food tolerance. Then plan calories, carbohydrates, fluids, sodium, and backup foods by hour. Vert’s Nutrition Planner helps runners turn those race details into a practical fueling plan.
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