Ultramarathon Nutrition Guide: What to eat before, during, and after an Ultra

Running ultramarathons places a massive demand on the body, not only during the race itself but also throughout training and recovery. Covering such long distances means you’re constantly burning calories, and your nutrition strategy needs to support both performance and overall health. 

That means fueling properly during runs, while also eating enough in your daily diet to maintain a healthy body weight, energy balance, and strong immune system.

Speaking from personal experience as a competitive ultrarunner, one of the biggest challenges is simply eating enough. Between high training volumes, busy schedules, and the digestive stress of long runs, it can feel nearly impossible to keep up with the calories burned. 

But if you want to train consistently and perform at your best on race day, making nutrition a priority is non-negotiable.

At its core, fueling for ultra-endurance events comes down to a delicate balance between overall calories, carbs, and gut training.

In short, ultramarathon fueling isn’t just about eating—it’s about strategic, practiced fueling that keeps you steady for hours on end without blowing up your gut or your glycogen stores. It’s not easy, but dialing it in is one of the biggest performance unlocks for long-distance runners.

How to Fuel as an Ultra Runner

Each runner has unique nutritional needs, which makes it crucial to figure out what works best for your body.

I always recommend consulting with a sports nutrition professional who has experience with runners—and ideally endurance athletes themselves. They can assess your metabolic rate, determine your macronutrient and caloric requirements, and help you understand whether supplements are necessary.

That said, as a UESCA-certified ultramarathon coach and an ultrarunner myself, I’ve spent years learning both through education and practical experience what fueling strategies work for long-distance training and racing.

On a day-to-day basis, I stick to a well-balanced diet rich in protein, vegetables, and of course, carbohydrates, the cornerstone of endurance performance. I use healthy fats in moderation, but I’ll admit: I enjoy my share of “junk food,” too. 

As ultrarunners, we’ve earned those cookies. The key is moderation and consistency with your overall nutrition plan.

And let’s not forget the fun part: carb-loading before a big race. Not only is it enjoyable, but it’s also essential for topping off glycogen stores to power you through ultra-distance efforts.

Pre-Race: The Carb Loading phase

Before an ultra, I take three days to increase my carbohydrate intake and load sufficiently.

During these days, I generally arrange my meals to be more carb-based. This also includes my mid-morning and mid-afternoon snacks.

Each of us will need a distinct amount of fuel depending on different factors such as weight and metabolism. Here, I will use myself as an example. 

During a typical training week, I consume 11 portions of carbohydrates and fruit throughout the day. However, during the three days leading up to an ultramarathon, that number increases to 21 portions, as carbohydrates like glucose and fructose are the preferred fuel sources for our muscles.

A pretty big difference.

In addition, my meal plan includes a specific number of fats, proteins, and vegetables, but let’s focus on the carbs. 

My 21 portions of carbohydrates are distributed throughout the day as follows. I have included some examples of what constitutes “1 portion of carbs” so you can get an idea of the quantities:

• Breakfast: 3 carbs = 3 slices of toast, 1 sugar = 1 teaspoon of honey / 2 fruits = 1 large banana
• Mid-morning snack: 1 carb = ⅛ cup granola / 1 dairy = 1 individual-sized yogurt /1 fruit = ½ cup strawberries
• Lunch: 4 carbs: = ⅔ cups couscous + 1 cup sweet potato
• Mid-afternoon snack: 1 carb = ¾ cup cereal / 1 dairy = 1 cups skim milk / 2 fruits = 1 banana
• Dinner: 4 carbs: = 2 cups pasta

And can you believe these are only the carbs? Adding the correct portions of proteins, vegetables, and fats completes each meal. 

In addition to your nutrition, your hydration strategy for endurance exercise is key, too.

Be sure to stay well-hydrated during the days leading up to your race.

I add a sports drink full of electrolytes to my carb-loading days to aid hydration and carb intake, and to prevent hyponatremia, which can occur when fluid intake is limited to water and electrolytes become depleted.

The Golden Rule of Race Day

As ultrarunners, we need to apply the golden rule for ultrarunning to absolutely everything we do. 

Do not try anything new on race day. This also includes the days previous when referring to food and hydration.

I am a creature of habit and follow this rule to a T. Why would I change something that works for me?

My pre-race dinner has been the same for the past decade. Even when traveling for a race, I cook and bring Giada de Laurentiis’s lemon pasta along with me wherever I go.

My friends may snicker at me while at the restaurant enjoying a meal out the night before the big day, but I don’t mind. There is no way I’m taking a chance of eating something that may not agree with me, putting at risk the outcome of a day I have worked so hard for. 

Now that we’ve prepared, let’s take a look at race day.

My Pre-Ultramarathon Breakfast

Now, I know it may seem excessive, but I always eat breakfast 2–3 hours before any race, and I recommend you do the same, to give your body enough time to digest and convert that food into usable energy.

My personal “breakfast of champions” for ultramarathons is a bagel smothered with honey (and yes, I pack one with me when I travel to races).

Other great options include:

• Oatmeal with banana and nut butter – a classic, balanced mix of carbs, fat, and protein.
• White rice with scrambled eggs – easy to digest and a favorite among many elite ultrarunners.
• Toast with jam and a side of Greek yogurt – quick carbs plus a bit of protein.
• English muffin with peanut butter and sliced banana – a portable and satisfying treat.
• Cereal with almond milk and berries – simple and light, good for nervous stomachs.

Eating a few hours ahead will leave you feeling strong at the start line, but you may still need a little boost right before the gun goes off. That’s why I always take a gel about 15 minutes before the race to top off glycogen stores and start energized.

Ultramarathon Nutrition Tips: Race Strategy

Each of us must carefully plan our nutrition and hydration strategy well in advance of the actual race. What we eat and drink during our ultramarathon needs to be practiced repeatedly in all of our long runs during the training process.

I suggest you try absolutely everything out there to see what works best for you. There are countless gels, bars, gummies, carb and electrolyte-filled drinks on the market just waiting for you to test out. 

As ultra-runners, it is also essential to try solid food while training. During a longer ultramarathon like an 80k, 100k, 100-miler, your body will be begging you for some real food.

It’s helpful to try it out beforehand so you can get used to running while chewing a peanut butter sandwich. 

To calculate the number of carbohydrates needed during a race, use the following equation:

Weight in kilos = carbohydrates per hour you need to consume

In my case, I weigh 51 kilos, so I need to consume 51 grams of carbohydrates per hour during my races. It’s essential to note that I am referring to grams of carbohydrates, not calories. 

Regardless of what you choose to consume, ensure that you track your total carbs each hour to maintain a consistent energy flow.

On the back of each product, a nutrition label is provided for your reference.

When checking, be sure you pay attention to the serving size the nutrition facts represent. It’s easy to misread a label, as sometimes it refers to a larger quantity of the product in the actual packet. This could inadvertently throw off your entire plan.

Gels can range anywhere from 16 – 25 grams of carbs, depending on which ones you choose, and sports drinks also have a wide range of carb intake. That’s why it is imperative to check every single label and calculate your intake with care. 

Choose to consume what works best for you, whether it’s gels, carb-filled hydration, sandwiches, or a combination of all of these. 

Figuring out your nutrition race strategy may take some time, and there will surely be a lot of trial and error, but keep at it until you perfect it.

Most of us focus on training our body and mind, but training our gut is just as important.

The most important thing is to consume enough carbohydrates during your race to avoid hitting the wall. Controlling our food is one of the few things we have power over, so let’s take advantage of it and give ourselves the best shot at finishing our race happy and healthy.

Race Hydration

To determine your optimal hydration for ultramarathons, it’s essential to undergo a sweat test. This helps calculate how much fluid you lose per hour, which in turn tells you how much liquid you’ll need to replenish during training and racing.

When taking a sweat test, try to simulate your race conditions as closely as possible—consider the climate, terrain, and intensity of your effort. This is especially crucial if you’ll be racing in hot and humid weather, since sweat rates can increase dramatically.

How to do a sweat test:

1. Weigh yourself before your run (wearing as little clothing as possible, ideally dry).
2. Run for 60 minutes at race effort in conditions similar to your target race.
3. Do not drink anything during the test.
4. After the run, towel off excess sweat and weigh yourself again in the same clothing.
5. The weight difference in pounds equals fluid loss in pints (or in kilograms, equals liters).

 Example: If you lose 2 lbs (≈0.9 kg) in an hour, that’s about 1 liter of fluid loss per hour.

After calculating your liquid loss, aim to replace at least 80% of that figure during your race. This ensures you stay well-hydrated while also avoiding the risks of overhydration.

Pro Tip: You Can Drink Your Carbs

I have had great luck drinking my carbs while racing, which kills two birds with one stone.

I get to hydrate while consuming my fuel at the same time. I don’t have to worry about carrying an array of products or eating a lot of solid food. Popular drink-mix options include Tailwind, Maurten, Skratch, and Precision Fuel & Hydration carb drinks. These products deliver both electrolytes and carbohydrates in an easy-to-digest form, even during long hours on the trail.

That said, I always bring a backup option just in case. Solid fuel options, such as gummies, Stroopwafels, energy gels, or even simple snacks like pretzels or bananas, can be lifesavers if your stomach craves something different mid-race.

It’s always better to be over-prepared than underprepared. Having variety means you’ll be able to adapt if your primary fueling plan doesn’t sit well on race day.

Calculating ultramarathon trail race finishing times is always a challenge—terrain, weather, and altitude can all shift your energy needs—so having flexible fueling strategies is key.

How Much To Carry?

Always overshoot and bring more than what you think you may need. As a backup, you always have the aid stations to refill if you are low on fuel.

If you plan to use aid-station nutrition instead of bringing your own, be sure to know what they will have and practice using those items beforehand to guarantee they work for you.

Post-Race Nutrition

To ensure a successful recovery, you must continue to fuel your body after an ultramarathon. Your muscles are depleted, your glycogen stores are low, and your body has undergone hours of physical and mental stress. What you do in the hours immediately after the race can make a huge difference in how quickly you bounce back.

Everyone reacts differently upon finishing an ultramarathon. Some runners cross the line ravenous, ready to devour anything in sight, while others feel nauseous or too exhausted to even think about food. Regardless of how you feel, recovery fueling is non-negotiable.

Aim to take in a recovery drink within 30 minutes of finishing. This window is crucial because your muscles are primed to absorb nutrients and begin repairing. Look for a drink with a 3:1 or 4:1 ratio of carbohydrates to protein. This helps replenish glycogen while kickstarting muscle repair. 

After that, try to eat a balanced meal within two hours. 

Focus on:

• Carbohydrates to restock energy stores (rice, pasta, potatoes, whole grains).
• Protein to repair muscle tissue (chicken, fish, eggs, beans, tofu).
• Healthy fats to reduce inflammation and support hormone balance (avocado, olive oil, nuts, fatty fish).
• Electrolytes and fluids to rehydrate (broth-based soups, coconut water, or simply water with added electrolytes).

It’s also smart to listen to cravings; they’re often your body’s way of signaling what it needs. Some runners crave salty foods to replenish their sodium levels, while others opt for sweet foods to replenish their carbohydrate stores quickly.

Finally, remember recovery nutrition isn’t just about the first meal—it’s a 24–48 hour process. Continue to eat nutrient-dense meals and snacks, hydrate consistently, and avoid under-fueling in the days following your race.

This sets you up not only for a faster recovery but also for long-term health and future training. Do everything possible to assist your system in recuperating as best it can, to suffer as little as possible in the days to follow. 

Ultramarathon nutrition must be taken seriously to achieve positive race experiences and outcomes. Taking care of what you consume will enhance your performance and help you reach your maximum potential. 

So let’s eat up!

If you are having trouble reaching your minimum calorie intake, check out our guide to high-calorie snacks:

High Calorie Foods: 12 High Calorie Foods For Effective Weight Gain