Fueling for a 100-Mile Race: Your Ultimate Nutrition Diet Plan

October 28, 2025 •

4 min read

Did you know that finishers of 100-mile races consistently consume around 70g of carbohydrates per hour, while non-finishers average less than 45g? Mastering how do you fuel for a 100-mile race is a crucial factor that separates those who cross the finish line from those who don't. A strategic nutrition plan is as essential as your physical training to endure the extreme physiological demands of ultra-running.

Quick Summary

A successful ultramarathon depends on a meticulous nutrition strategy encompassing proper carbohydrate loading, hourly in-race calorie and electrolyte intake, and post-race recovery to replenish glycogen and repair muscles. Adaptability and training your gut are vital for managing the duration's unique demands.

Key Points

Start your pre-race carb load early: Begin increasing your carbohydrate intake 48–72 hours before the race to maximize glycogen stores.
Fuel consistently from the beginning: Consume 200–400 calories and 60–90 grams of carbohydrates per hour to avoid bonking.
Train your gut to handle high carb intake: Practice your race-day nutrition strategy during long training runs to minimize gastrointestinal distress.
Combat palate fatigue with diverse fuel sources: Rotate between sweet gels and savory real foods like salted potatoes or broth during the race to ensure you keep eating.
Prioritize hydration and electrolytes hourly: Drink 16–32 ounces of fluid per hour and consume 500–1000 mg of sodium to prevent dehydration and cramping.
Embrace solid foods in the later stages: As intensity drops in longer ultras, real food can be more appealing and provide sustained energy than relying solely on gels.
Focus on post-race recovery nutrition: Immediately after the race, consume a 4:1 carb-to-protein ratio meal to begin the recovery process.
Nothing new on race day: Stick to the foods and products you've successfully tested during training to avoid unwanted surprises.

The Foundation: Your Pre-Race Carb-Loading Strategy

Proper carbohydrate loading is paramount for stocking your body's primary fuel source, glycogen. Starting this process in the days leading up to your 100-mile race can significantly boost your energy reserves.

48 to 72 hours before the race: Aim to consume 8–12 grams of carbohydrates per kilogram of body weight per day. For a 70kg runner, this means consuming 560g to 840g of carbs daily. Focus on compact, low-fiber sources to prevent gastrointestinal (GI) issues during the race.
Emphasize easily digestible carbohydrates: Opt for white rice, pasta, bagels, oats, and potatoes rather than high-fiber whole grains.
Prioritize hydration: Increase your fluid intake in the days leading up to the race. A good rule of thumb is to drink 1.5 times your body weight in fluid each day.
Morning of the race (3-4 hours prior): Have a final, carb-heavy meal to top off your glycogen stores. Options include oatmeal with fruit, a bagel with jam, or toast.

During the Race: Hourly Fueling and Hydration

During a 100-mile race, your body's energy needs are immense, and relying on stored energy alone is not enough to finish. You must fuel early and often to avoid hitting the wall.

The Rule of Early and Often

Calories per hour: Target 200–400 calories per hour, with many elite runners consuming on the higher end of this range.
Carbohydrates per hour: Aim for 60–90 grams of carbs per hour to maintain blood glucose levels. In some cases, experienced athletes can train their gut to tolerate up to 120g/h using dual-source carbs (glucose and fructose).
Hydration: Drink 16–32 ounces of fluid per hour, adjusting based on environmental conditions and individual sweat rates.
Electrolytes: Replenish sodium and potassium lost through sweat to prevent cramping and dehydration. A general guideline is to consume 500–1000 mg of sodium per hour.
Introduce protein: In longer events (over 8–10 hours), consuming 5–10g of protein per hour can help preserve lean mass and reduce fatigue.

Combatting Palate Fatigue: Real Food vs. Sports Nutrition

Sweet-flavored sports products can become unpalatable after hours on the trail. Diversifying your food choices is essential for maintaining consistent calorie intake.


Fuel Type	Benefits	Best Used During	Potential Drawbacks
Sports Gels/Chews	Quick energy, easy to carry, and portion-controlled.	Early race (first 4-6 hours) or during high-intensity periods.	Can cause stomach distress if overconsumed; flavor fatigue.
Sports Drinks	Combines hydration, carbs, and electrolytes in one product.	Early race, especially in warmer weather; a baseline fuel source.	Can be too sugary, leading to nausea; hard to separate calories from hydration.
Salty Snacks	Replenishes sodium and combats sweet fatigue.	Mid to late race (after 6-8 hours); at aid stations.	Can be dry and difficult to swallow if not consumed with enough fluid.
Real Foods	Provides comfort, satiety, and a mix of macronutrients.	Mid to late race (after 8+ hours) when intensity is lower.	Can be difficult to digest; potentially bulky to carry.

Post-Race Recovery: The Critical First 24 Hours

Once you cross the finish line, your body begins the long process of recovery. What you consume immediately after the race can significantly impact how quickly you rebound.

Rehydrate: Continue to drink plenty of fluids with electrolytes to replace losses. Don't stop hydrating just because the race is over.
Replenish: Within the first 30-60 minutes post-race, consume a meal or shake containing carbohydrates and protein. A 4:1 carb-to-protein ratio is ideal for kick-starting glycogen replenishment and muscle repair.
Listen to your body: Your appetite may be low immediately after a 100-miler. If you can't stomach a full meal, opt for easily digestible snacks like a smoothie or yogurt. Don't force yourself to eat; start small and build up as you can.
Avoid refined sugars: While tempting, refined sugar drinks can cause inflammation and delay gut recovery. Focus on nutritious options.

A Note on Gut Training

Your stomach needs to be trained just like your legs. Start practicing your race-day fueling plan during your long training runs 8–12 weeks before the race. This allows your gut to adapt to absorbing the high carbohydrate load and reduces the risk of GI issues on race day. Experiment with different products and real food options in training to discover what your body tolerates best.

Conclusion

Successfully fueling for a 100-mile race requires a holistic and adaptable nutrition plan, honed through consistent practice during your training cycle. From strategic pre-race carb loading to meticulous hourly fueling and critical post-race recovery, every nutritional decision plays a pivotal role in your performance. By training your gut, diversifying your food sources, and prioritizing hydration and electrolytes, you can transform your nutrition into a powerful advantage. The ultimate goal is to avoid the dreaded bonk and keep your energy, mood, and mental clarity steady across the punishing miles. A well-executed fueling strategy is the foundation of a successful ultra-running experience.

Frequently Asked Questions

The recommended hourly carbohydrate intake is 60–90 grams. Some experienced ultra-runners can train their gut to tolerate up to 120 grams per hour, especially when using dual-source carbs (glucose and fructose).

To avoid 'hitting the wall,' or 'bonking,' you must fuel consistently from the beginning of the race. This prevents the depletion of your body's limited glycogen stores by providing a steady supply of external carbohydrates.

You should start eating early and often, ideally within the first 20-30 minutes of the race. Waiting until you feel hungry means you are already behind on your fueling.

Combat palate fatigue by rotating between a variety of food sources. This includes switching from sweet sports products to savory real foods like salted potatoes, broth, or pretzels, especially in the later stages.

Aim to drink 16–32 ounces of fluid per hour, adjusting based on temperature, humidity, and your personal sweat rate. It is also important to include electrolytes to aid fluid retention.

Yes, solid foods can be a great option, especially in the mid to late stages of an ultra when your running intensity is lower and you may crave more substantial fare than gels. Options like rice balls, sandwiches, and salty snacks are popular choices.

Gut training is crucial for conditioning your digestive system to handle the high caloric and fluid intake required during an ultra-marathon. Practicing your race-day fueling plan in training helps reduce the risk of GI issues on race day.

For carb-loading, begin 2 to 3 days before the race by increasing your carbohydrate intake to 8-12 grams per kilogram of body weight per day. Focus on easily digestible, low-fiber carbs to maximize glycogen storage.