Running a marathon is no small feat and many runners fear hitting the inevitable “wall”...but proper fueling and hydration can lead to you crossing the finish line still feeling strong! So, how exactly do you achieve an optimal fueling plan for race day? Do your pre- and post-race meals matter? How often should you be fueling throughout the race? Let’s dive into the details:

What are carbohydrates?

Carbohydrates are an essential macronutrient that our bodies need in larger quantities. They are the body’s preferred energy source for both high-intensity and low-to-moderate intensity activities and are especially important during endurance events (like marathons). There are three types of carbohydrates:

Sugar
- Simple sugars are referred to as monosaccharides or disaccharides. These carbohydrates are quickly digested and absorbed and can be naturally occurring (ex: fruit, honey) or added during processing (ex: candy, fruit jam)
Starch
- Starches are complex carbohydrates AKA polysaccharides. These carbohydrates consist of multiple sugar molecules linked together and are broken down more slowly into individual sugar molecules for energy (ex: bread, potatoes)
Fiber
- Fibers are a type of polysaccharide found in plant foods (ex: fruits, vegetables, whole grains) that can’t be fully digested and absorbed by the body. These carbohydrates promote gut health, help regular blood sugar levels, and support appetite control, but may cause stomach upset if consumed too close to physical activity.

Carbohydrate Use and Storage

Carbohydrates are broken down by the body into glucose to provide energy to the brain, muscles, and nervous system. When the amount of glucose in your bloodstream exceeds the amount that your body readily needs, then it can be stored for later use as glycogen. During a marathon, your body relies on both glucose in the bloodstream and glycogen stored in the liver and muscle for energy. As you power through mile after mile, your glycogen stores deplete, making it essential to maintain a consistent intake of carbohydrates to prevent fatigue and sustain energy levels.

Fun Fact: Up to ~500 grams of carbohydrate can be stored as glycogen in the liver and muscle.

Daily Carbohydrate Recommendations for Athletes

Carbohydrate needs can vary depending on the intensity and duration of physical activity. Below are general guidelines:

how does fueling for competition differ from training?

Athletes should aim to enter race day with fully saturated glycogen stores and adequate glucose levels in the bloodstream. Nutrition before, during, and after the race is crucial for optimal performance and recovery. Let’s talk a little bit more about what each stage of fueling should look like to ensure you’re properly prepared and energized throughout your race.

The night before

The night before your big race, focus on consuming higher-carb meals with moderate protein, low fat, and low fiber. Prioritizing carbohydrates will help top off your glycogen stores, ensuring you have plenty of stored energy for race day. It’s also beneficial to focus on hyper-hydration and consider drinking tart cherry juice, which may help prevent muscle soreness and inflammation. Here’s what your plate could look like:

The morning of

Your pre-race meal should happen ~3 to 4 hours before your race and should focus on high-carb, moderate-protein, and low-fat/low-fiber foods to provide quick energy without causing stomach upset. You’ve heard it before, but I’ll say it again — stick with foods that you’ve tried during training and know will work for you! Here are a few combinations to consider:

Intra-Race Fueling

You’ve officially crossed the start line — now what does fueling look like? During the race is when you’ll prioritize quickly digestible carbohydrate sources! Generally speaking, if your marathon will take you more than two hours to complete, then you should be consuming 60 to 90 grams of carbohydrate per hour. There are plenty of options on the market including:

Gels
- Gu, Honey Stinger, Huma, Maurten, Spring Energy, SIS, NeverSecond, CARBS, UCAN
Chews/Blocks
- Skratch, Gu Energy Chews, Clif Bloks, Honey Stinger Chews, Bonk Breakers
Liquid Fuel
- Gatorade, Skratch Labs, Tailwind
Real Foods
- Swedish fish, crackers, pretzels, granola bars, dried fruit

Creating a fueling plan is highly individualized and largely depends on personal preference. During your race, fuel sources can be combined to meet your goal of 60 to 90 g/carbs per hour. Here are some examples of what fueling might look like for someone running a 4-hour marathon:

Post-Race Fueling

You’ve officially crossed the finish line and are ready to celebrate the HUGE accomplishment of running 26.2 miles! What does your body need to recover efficiently? Within 30 minutes of finishing your race, be sure to prioritize simple carbohydrates and protein (preferably 4 grams of carb:1 gram of protein). Too much fiber and/or fat immediately after a race can cause stomach upset and slow absorption of energy that your body needs immediately.

Need help determining your individualized plan?

Reach out to GracesGrit for more information on our individualized services including our Race Day Fueling Plan and Assessment.

References:

Gatorade Sports Science Institute . Dietary Carbohydrate for Female Athletes.; 2024. Accessed April 1, 2025. https://performancepartner.gatorade.com/content/resources/pdfs/sports-nutrition-hydration-female-athletes-ch-1.pdf?v=2

Farrow O, Smith C, Kolodziejzyk K, Boateng T. Sports Nutrition Evidence Summary. Dietitian Success Center; 2023.

How Should I Fuel For a Marathon?