What is the best energy for a run?

January 11, 2026 •

4 min read

Carbohydrates are the primary fuel source for runners, especially at higher intensities, according to sports nutritionists. However, the best approach depends on the run's duration and intensity.

Quick Summary

Carbohydrates are key for efficient muscle energy during a run. While fats provide fuel at lower intensities, carb stores need replenishing for longer or faster runs. Strategic intake of carbs, fluids, and electrolytes before and during a run is critical.

Key Points

Carbohydrates are the primary fuel: The body's preferred energy source for high-intensity exercise is glycogen, stored carbohydrates.
Fat fuels lower intensity: At a slower pace, the body uses a higher percentage of fat for energy, which is a vast reserve.
Timing pre-run fuel is critical: Eat a larger, carb-focused meal 2-4 hours before a long run, or a small, easily digestible carb snack 30-60 minutes before shorter efforts.
Mid-run fuel prevents bonking: For runs over 60-90 minutes, replenish glycogen stores with 30-60g of carbs per hour using gels, chews, or sports drinks.
Hydration is non-negotiable: Drink water before, during, and after a run, and use electrolyte drinks for longer sessions to replace lost minerals.
Protein aids recovery, not fuel: While not a primary energy source during exercise, protein is essential after a run to repair and rebuild muscle tissue.
Individual needs vary: Every runner's optimal fueling strategy differs based on body size, intensity, and duration, so test and adjust in training.
Avoid high fiber/fat before races: High-fat and high-fiber foods can cause gastrointestinal distress and should be avoided in the hours leading up to a race.

The Science of Fueling Your Run: Carbohydrates vs. Fat

For most runs, the body uses a combination of carbohydrates and fats for energy. Understanding how and when the body utilizes each is the key to creating an effective fueling strategy.

Carbohydrates (Glycogen): The body stores carbohydrates as glycogen in the muscles and liver. It acts as the primary fuel source for intense or sustained efforts. Glycogen is broken down into glucose, the fastest and most efficient energy source. These stores are limited and can be depleted in as little as 90 to 120 minutes of hard running. This is a critical factor for endurance athletes, as 'hitting the wall' is a direct result of glycogen depletion. To maximize performance, runners must top up these stores before and replenish them during longer sessions.
Fats: Fat reserves are a virtually limitless energy source compared to glycogen. Fat is the primary fuel source for lower-intensity, longer-duration activities, where oxygen is readily available to break it down. While the body can become more efficient at burning fat through specific training, it is a slower process than using carbohydrates and cannot sustain high intensity.

Pre-Run Fueling: Timing is Everything

Nutrition leading up to a run is as important as the fuel consumed during the run. Proper timing helps prevent digestive issues and ensures energy stores are topped up.

The Night Before a Long Run

The night before a race or long run, focus on complex carbohydrates. This strategy, known as 'carb-loading,' maximizes the body's glycogen stores. A balanced meal might consist of:

Pasta or rice with a lean protein source
Sweet potatoes
Whole-grain bread
Limited fiber and fat to avoid stomach upset

The Morning of the Run

On the day of the run, timing your meal depends on the meal's size and the distance covered. For most runners, a light snack 30 to 60 minutes before a short run is sufficient, while a larger meal is best eaten 2 to 4 hours before a long-distance effort.

Quick-absorbing snacks (30-60 minutes before):

A banana
Energy chews or a gel
Small toast with jam

Full pre-run meals (2-4 hours before):

Oatmeal with fruit and honey
A bagel with peanut butter
Rice bowl with scrambled eggs

Mid-Run Fueling for Sustained Performance

For runs lasting longer than 60-90 minutes, replenishing carbohydrate stores mid-run is necessary to prevent 'bonking'.

Fueling Options

Energy Gels and Chews: These provide a concentrated, easily digestible source of carbohydrates, typically 30-60 grams per hour for a long run. Isotonic gels, for instance, are thin and can be consumed without extra water.
Sports Drinks: Many sports drinks combine carbohydrates with electrolytes like sodium and potassium, which are lost through sweat. A 6% carbohydrate solution is recommended to avoid stomach upset.
Whole Foods: Some runners prefer more natural options like dates, dried fruit, or homemade energy bites. These provide energy but can be harder to digest during high-intensity efforts. The key is to test any fuel strategy during training runs to avoid race-day surprises.

Comparison of Running Fuel Sources


Fuel Source	Primary Function	Ideal for...	Key Components	Notes
Carbohydrates	Main energy for high-intensity, long duration	All distances, especially high-intensity sprints, 10Ks, half marathons, marathons	Glucose, Glycogen, Sports drinks, Gels, Chews	Rapidly absorbed; limited storage requires re-fueling during long runs.
Fat	Main energy for low-intensity, long duration	Long, slow distance (LSD) training runs; Ultra-marathons	Nuts, Seeds, Avocado, Fatty Fish	Slower to metabolize; large energy reserve; metabolic efficiency can be trained.
Protein	Muscle repair and recovery; minimal fuel during run	Post-run recovery meal; Ultra-marathons (small amounts during)	Lean meats, Fish, Eggs, Tofu, Protein powders	Not a primary fuel source, but essential for muscle adaptation and preventing breakdown.
Hydration/Electrolytes	Regulates temperature; prevents cramps; delivers nutrients	All runs, especially longer, hotter ones; mid-run	Water, Electrolyte tablets, Sports drinks	Replaces fluids and minerals lost through sweat; critical for performance.

Hydration and Electrolytes for Runners

Fluid intake is critical to performance, especially for runs over 60 minutes or in warm conditions. Dehydration can lead to fatigue, cramps, and reduced performance, while overhydration can be dangerous.

Before: Drink 16-20 ounces of water 2 hours pre-run and a final 6-8 ounces 15 minutes before starting.
During: Consume 5-10 ounces of fluid every 15-20 minutes, potentially from a sports drink for electrolytes and carbs.
After: Replenish fluids by drinking 16-24 ounces of water for every pound lost.

Conclusion

Ultimately, the best energy for a run is a well-planned, personalized nutrition and hydration strategy. For most runners, carbohydrates are the most important immediate fuel source, supplemented by fat during lower-intensity efforts. Proper timing of meals and fluid intake is crucial for maximizing performance and recovery. Experiment during training with different foods, gels, and sports drinks to find what works best, ensuring the energy needed to cross the finish line feeling strong.

Practical Training and Racing Fuel Guide

For runs under 60 minutes, pre-run hydration is usually sufficient, with no mid-run fueling necessary for most people.
For runs over 60 minutes, practice a mid-run fueling strategy using gels, chews, or drinks to avoid stomach distress on race day.
During long, slow training runs, the body can be trained to utilize fat more efficiently by reducing carbohydrate intake, but this should be done with caution to avoid underfueling.
After every run, especially longer sessions, consume a combination of carbohydrates and protein within 30-60 minutes to replenish glycogen and repair muscles.
For ultra-marathons (over 4-5 hours), supplementing with a small amount of protein (around 5g per hour) may help prevent muscle breakdown.

Frequently Asked Questions

For runs under an hour, a small, easily digestible carbohydrate-rich snack like a banana, toast with jam, or a handful of cereal is often sufficient and can be eaten 30-60 minutes before starting.

Energy gels are not necessary for runs under 60-75 minutes for most people. They are primarily designed for replenishing carbohydrates during longer runs (over 90 minutes) or high-intensity sessions where glycogen stores become depleted.

Protein is crucial for muscle repair and building after a run, but it is a minimal energy source during the exercise itself. Consuming protein with carbohydrates post-run helps with recovery and adaptation.

Running on an empty stomach is okay for some short, low-intensity runs, but it can lead to fatigue and lower performance. For longer or higher-intensity runs, fueling beforehand is recommended to prevent glycogen depletion and sustain energy levels.

You should use electrolyte-enhanced drinks for runs lasting longer than 60 minutes, especially in hot or humid conditions. This replaces the sodium, potassium, and other minerals lost through sweating.

The night before a long race, you should 'carb-load' with a meal rich in complex carbohydrates like pasta, rice, or potatoes. Avoid high-fiber and high-fat foods to prevent digestive issues.

'Hitting the wall' refers to the sudden and overwhelming fatigue that occurs when your body's stored glycogen is depleted during a long run, forcing you to slow down dramatically.