By Manuel Attard, M.Sc RD

The best diet for marathon training includes a well-planned, strategic eating plan to fuel your long runs. As you aim to improve your performance and endurance for a marathon, the role of your diet becomes critical. In this article, we’ll explore the strategies that can help fuel your marathon training and power you through race day.

The Discipline of Distance Running

Distance running is not just about putting on your sneakers and clocking miles; it requires mental and physical resilience. Whether you’re a recreational runner aiming to improve your fitness level or an elite athlete targeting peak performance, the principles of distance running remain the same.

Weekly long runs are important for building endurance to prepare for the marathon. Your diet for marathon training must include plenty of nutrients to fuel you on long training days.

The Role of Diet in Marathon Training

As a marathon runner, your dietary choices greatly influence your performance and overall well-being during training and racing. Let’s delve deeper into the best diet for marathon training. Here are some specific targets and recommendations to help you optimize your nutrition strategy:

Carbohydrate Intake: Fueling Your Performance

Carbohydrates are the fuel of distance running. Carbs are your body’s primary energy source, and managing your carbohydrate intake is crucial for peak performance. Here are some specific recommendations for carb intake while marathon training:

Daily Intake: On regular training days, aim for a carbohydrate intake that's approximately 50 to 65% of your total daily calories. This percentage can vary depending on your training volume and intensity.
High-Volume Training Days: On days when your training volume is high, increase your carbohydrate intake to around 7 to 10 grams of carbohydrates per kilogram (or 2.2 pounds) of body weight. For a 68-kilogram or 150-pound person, this would range from 476 grams to 680 grams. This ensures you have enough glycogen stores to sustain your energy levels during long runs and intense workouts.
Low-Volume or Rest Days: On lower-volume training days or rest days, you can scale back your carbohydrate intake, but it should still make up a significant portion of your diet. Aim for around 5 to 7 grams per kilogram (2.2 pounds) of body weight. So, for a 68-kilogram or 150-pound person, this equals 350 to 476 grams of carbs.
Carbohydrate Sources: Prioritize nutrient-dense carbohydrate-rich foods such as whole grains (brown rice, quinoa, whole wheat pasta), starchy vegetables (sweet potatoes, butternut squash), and fruits. These foods provide carbohydrates, essential vitamins, minerals, and fiber. Limit your intake of overly processed, refined carbs as much as possible, which includes white bread, baked goods, and many pre-packaged snack foods.
Sports Fuel: For intense training sessions or during a marathon race, consider incorporating additional carbohydrate sources like sports drinks, energy gels, or carbohydrate-rich snacks to maintain energy levels and prevent glycogen depletion. We’ll get more into energy gels and drinks in the hydration section.

Related Post: Running Fuel Guide

Protein: Building Blocks for Recovery

Protein plays a critical role in muscle repair and adaptation, aiding in your recovery process. Protein should be a vital part of your diet for marathon training. Here’s how to incorporate protein into your nutrition plan:

Daily Protein Intake: Aim for a daily protein intake of approximately 1.2 to 2.2 grams per kilogram (or 2.2 pounds) of body weight. This range accounts for varying training volumes and individual needs, with the higher end offering more nourishment for runners with high-mileage runs and high-intensity workouts like speed workouts.
Distribution: Include protein-rich foods in every meal and snack throughout the day. Make lean protein sources like nuts, chicken, turkey, lean beef, fish, tofu, beans, and legumes part of your regular diet for marathon training.
Post-Workout Protein: After intense training sessions or races, prioritize a post-workout meal or snack that includes around 20 to 25 grams of high-quality protein. This helps with muscle recovery and adaptation.

Gastrointestinal Health: Avoiding Discomfort

Gastrointestinal (GI) upset during hard runs is a common concern. To minimize discomfort, consider the following recommendations:

Pre-Training Meal: Consume a balanced, low-fiber meal around 2 to 3 hours before your run. A combination of carbohydrates, lean protein, and healthy fats can provide sustained energy without overwhelming your digestive system.
Avoid High-Fiber Foods: Reduce your intake of high-fiber foods like bran cereals, high-fiber fruits, and vegetables immediately before running. High fiber can lead to GI distress.
Liquid Meal Supplements: Sometimes, liquid meal supplements or low-fiber options like smoothies can be easier on your stomach before intense training sessions or races.

Related Post: What to Eat Before Running

Hydration: Maintaining Fluid Balance

Staying adequately hydrated is crucial for marathon training. To ensure you’re adequately hydrated, you can use these guidelines as a general reference point:

Daily Hydration: Aim to drink enough fluid each day to replace the fluids you lose through training. Temperature, sweat rate, exercise intensity, and duration influence your daily fluid needs.
Rehydration: After a run, it’s essential to rehydrate. Aim to replace approximately 150% of the fluid volume lost during your run over the next 4 to 6 hours. Water should be your primary choice for rehydration after regular training runs. You may also want electrolyte drinks and sports fuels for long runs, speed work, or training in heat and humidity.

Eating Before a Run

Fuel and hydration are crucial to prevent fatigue during a race. For longer distances like the marathon, it’s essential to carbohydrate load in the 24 to 48 hours before your race. Carb loading can increase glycogen stores, improving fuel availability during the race. Low-fiber foods, reduced protein or fat intake, and liquid carbohydrate foods can help minimize the risk of stomach issues during the race.

Your pre-event meal is a crucial opportunity to top up glycogen stores and optimize hydration. A light, low-fiber, carbohydrate-rich snack 1 to 2 hours before the race can work well for early morning races. For later races, have a larger meal 3 to 4 hours before, followed by a smaller snack or carbohydrate-containing fluid closer to the race.

Try different foods and eating times as part of your diet for marathon training so you can find what works best for you. Everyone has different digestion and absorption rates, so find a strategy that helps you stay energized and replenishes lost calories and hydration.

Eating and Drinking During A Marathon

For long-distance races like the marathon, you’ll need to take some fuel during the race. Marathon runners should consume 30 to 60 grams of carbohydrates per hour to prevent muscle fatigue and maintain pace and performance.

Opt for easily digestible carbohydrate-rich options with minimal fat, fiber, and protein. Sports gels, bars, and drinks are convenient options. Many runners experiment with different options during training to find what works best for them.

Some runners also take fuels with caffeine during the marathon for an added performance boost.

Recovery

Your glycogen stores will be depleted after high-intensity training sessions, races, or long runs. A carbohydrate-rich meal or snack shortly after finishing helps speed up your recovery. Include around 20 to 25 grams of high-quality protein to help with muscle repair. Healthy fats can reduce inflammation. Don’t forget to rehydrate after your long runs by drinking fluids, primarily water, to replace sweat losses. Prioritize nutrient-rich whole foods for recovery and stay away from processed foods as much as possible.

Additional Marathon Nutrition Tips

Practical Testing: Practice fueling and fluid strategies during training - especially on long runs - to ensure you’re comfortable eating and drinking while running.
Monitor Iron Levels: Distance runners, especially women, are at risk of low iron levels due to increased losses and/or low intake of iron-rich foods. Low iron levels can lead to fatigue and hinder performance, so it’s crucial to check your iron status with a healthcare professional and consult a sports dietitian for further support.

Need a marathon training plan to conquer your next big race? Head to the Runstreet Training Center for personalized training programs to help you become a better runner. Happy running - and eating - to you!

Manuel Attard, M.Sc RD. is a sports dietitian and nutritionist with a master’s in Human Nutrition from the University of Glasgow. He is based in Malta.

Best Diet for Marathon Training: Tips from a Nutritionist