How Often Should You Eat When Running a Marathon?

December 1, 2025 •

4 min read

According to sports dietitians, your body's glycogen stores can only sustain you for about 60 to 90 minutes of high-intensity exercise, highlighting the critical need for proper in-race nutrition. This guide explains exactly how often you should eat when running a marathon to avoid bonking and maintain your energy levels.

Quick Summary

Fueling frequency during a marathon is crucial for sustaining energy and preventing fatigue. The general recommendation is to start fueling 30 to 45 minutes into the race and continue consuming 30-60 grams of carbohydrates every 30-60 minutes thereafter. Factors like pace, body weight, and training level influence individual timing.

Key Points

Start Fueling Early: Begin fueling 30-45 minutes into the race, before your body’s glycogen stores are significantly depleted.
Aim for 30-60g Carbs Per Hour: Most runners should target this carbohydrate intake, with experienced athletes potentially consuming more.
Practice During Training: Never introduce a new fuel source on race day; always test products and timing during long training runs to avoid stomach issues.
Balance Fuel with Water: Always consume fuel, especially gels, with water to aid digestion and absorption.
Use Regular Reminders: Set a repeating alarm on your watch every 30 minutes to ensure consistent fueling throughout the race.

Why Your Marathon Fueling Strategy Is So Important

Proper fueling is the difference between a strong finish and 'hitting the wall'—the sudden, debilitating fatigue that occurs when your body runs out of stored glycogen. Your body primarily uses carbohydrates for fuel during a marathon. By strategically replenishing these stores throughout the race, you ensure a consistent energy supply to your working muscles and brain. This prevents performance decline, aids mental focus, and supports a faster recovery post-race.

The Science Behind Fueling Frequency

Your body can absorb and utilize a limited amount of carbohydrates per hour. The standard recommendation is to consume 30-60 grams of carbohydrates per hour, but some elite athletes and well-trained individuals can handle up to 90 grams or more by utilizing a mix of glucose and fructose sources. The timing and frequency of your intake are just as important as the quantity. Waiting until you feel depleted is a common mistake that can be hard to recover from. Instead, start fueling early and consistently.

Key Principles for Effective Marathon Fueling

Start Early, Stay Consistent: Begin taking your first dose of fuel about 30 to 45 minutes into the race, before your glycogen stores are significantly depleted.
Practice in Training: Never try a new fueling strategy or product on race day. Rehearse your exact plan during your longest training runs to train your gut and identify any issues.
Listen to Your Body: While general guidelines exist, individual needs vary. Pay attention to how your body responds and adjust your intake accordingly.
Combine Food and Drink: Your carbohydrate intake can come from gels, chews, and sports drinks. Remember to account for the carbs in your sports drinks when calculating your hourly intake.
Stay Hydrated: Fueling and hydrating go hand-in-hand. Always take your fuel with water to help with absorption and prevent stomach upset.

Comparison Table: Fueling Strategies by Runner Profile


Runner Profile	Carbohydrate Intake Per Hour	Intake Frequency	Fuel Type Examples
Novice Runner (4+ hour goal)	30–60 grams	Every 30-45 minutes	Gels, sports drinks, chews, bananas
Intermediate Runner (3-4 hour goal)	60–90 grams	Every 20-30 minutes	Gels, sports drinks, electrolyte chews
Experienced/Elite (<3 hour goal)	90+ grams	Every 15-20 minutes	High-potency gels, liquid carb mixes, electrolyte capsules

Practical Application: A Step-by-Step Approach

Develop a Plan: Based on your pace and estimated race time, calculate your hourly carbohydrate needs. For a typical runner aiming for 60g/hr, this means roughly two gels and a sports drink bottle each hour. Map out which mile markers or time intervals you'll take your fuel.
Trial Your Products: Use your long training runs to test your chosen gels, chews, or sports drinks. Do they sit well with your stomach? How do they taste over time? This practice helps your gut adapt to race day conditions.
Use Reminders: On race day, it's easy to get distracted. Set a repeating alert on your watch every 30 minutes to remind you to eat. You can also write your fueling plan on your hand or arm.
Balance Fuel and Hydration: As you consume concentrated carbs like gels, chase them with plain water. This ensures proper digestion and avoids gastric distress. Use sports drinks for some of your carb intake but be mindful of their contribution.
Don't Overdo It: More isn't always better. Consuming too many carbs at once can overwhelm your digestive system, leading to cramps and nausea. Stick to the amounts you practiced in training.

A Sample Fueling Schedule for a 4-Hour Marathoner

Pre-Race (3-4 hours before): Large, carb-heavy, low-fiber breakfast (e.g., oatmeal, bagel).
Race Start: Sip water/electrolyte drink. Take a gel 15 minutes before the start.
Mile 4 (~30-40 min): First energy gel or chews.
Mile 7 (~60-70 min): Second energy gel or chews.
Mile 10 (~90-100 min): Third energy gel or chews.
Mile 13.1 (Halfway): Use an aid station to take on water and assess how you feel.
Mile 16 (~150-160 min): Fourth energy gel or chews.
Mile 19 (~180-190 min): Fifth energy gel or chews.
Mile 22 (~210-220 min): Sixth energy gel or chews (consider a caffeinated one for a boost).

Conclusion

Determining how often you should eat when running a marathon depends on your individual needs and pace, but a consistent fueling schedule is non-negotiable for success. The consensus among sports nutritionists is to start early—about 30-45 minutes in—and refuel with 30-60 grams of carbohydrates every 30-60 minutes. The key to a successful marathon day is practicing this strategy repeatedly during your long training runs. This allows you to fine-tune your approach, train your digestive system, and build the confidence that your fueling plan will carry you to the finish line. Don't wait until you're tired or hungry; stay ahead of your body's energy demands from the very beginning.

Note: For further reading on comprehensive marathon training, including nutrition, check out the resources from organizations like TrainingPeaks.

Final Takeaway

Fueling during a marathon is a deliberate process, not a last-minute decision. By consistently eating every 30-60 minutes from the first hour onwards, runners can effectively prevent glycogen depletion and sustain performance throughout the race.

Frequently Asked Questions

'Hitting the wall' refers to the sudden and intense fatigue that occurs when your body runs out of stored glycogen. Consistent fueling with carbohydrates throughout the marathon provides a steady energy source, preventing this depletion and sustaining performance.

A good starting point is 30-60 grams of carbohydrates per hour. This amount can be adjusted based on your body weight, pace, and how your stomach tolerates different amounts during training. Experienced runners may tolerate higher doses.

Take your first energy gel or fuel source about 30 to 45 minutes into the race. This helps to top off your glycogen stores before they run too low and prevents you from playing catch-up later in the race.

Both can be effective, but gels and chews are often preferred during the race due to their quick absorption and easy portability. Some runners find that solid food earlier in the race works, followed by gels for faster absorption later on.

Over-fueling can lead to gastrointestinal distress, including cramps, nausea, and bloating. This is why practicing your fueling strategy during training is essential to determine your body's tolerance.

Yes, many sports drinks contain carbohydrates and electrolytes. You should factor in the carbohydrate content of your sports drinks when calculating your hourly intake to avoid overconsumption from gels and chews.

Yes, many runners successfully use real foods like bananas, dried fruit, or pretzels. The key is to test these foods extensively during training to ensure they don't cause stomach issues and to understand their carbohydrate content for accurate fueling.