Marathon Training & Nutrition: Fueling For Long Runs

Wednesday, September 27, 2006 - 9:02am

By Erica Lesperance, RD, LD

When training for a marathon, what you eat or do not eat before your long run can make or break your training session. At first, training runs will only last 30-60 minutes and a very basic hydration and nutrition plan is sufficient to maintain energy through the workouts. When those minutes stretch out past the hour mark, however, it’s more important to choose pre-run foods wisely to help you last through two to four hours of continuous running. Many runners question whether or not they should eat before runs and want to identify the best pre-training run foods. Since each person has unique preferences and aversions, there is no magic food that will ensure top performance for everyone. However, with a few guidelines and a bit of experimenting, you can find the foods that best support your needs.

Why should you eat before a marathon?

Your body can store enough to fuel only about two hours of continuous exercise. Many runs on a marathon training schedule exceed two hours and will require you to supplement your body’s stores. However, runners often suffer from abdominal discomfort due to the prolonged up and down movement of the stomach during a long run. The threat of intestinal chaos causes many runners to skip a pre-run meal. It is true that runners who avoid food before runs may be better off than those who chose foods that don’t agree with them. However, those who avoid food miss out on the three crucial functions of pre-run nourishment:

  • Eating before exercise helps to prevent low blood sugar, which can cause fatigue, blurred vision, and light-headedness and interfere with top performance.
  • If the correct foods are chosen, eating before a run can help postpone hunger and settle the stomach by absorbing gastric juices.
  • Food provides additional fuel for the muscles, which is especially important in prolonged exercise.

What should you eat before a marathon?

To determine the right pre-run foods for you, experiment with the following guidelines.

1.   Choose carbohydrates with a moderate-to-low glycemic effect to provide fuel for the marathon

Carbohydrates are divided into categories according to their ability to contribute glucose to the bloodstream, otherwise known as their glycemic effect. High-glycemic-index carbohydrates such as honey, Gatorade, white bread, and potatoes enter the bloodstream very quickly providing a sudden burst of energy. This is beneficial during and immediately after exercise, but is not recommended for a pre-run meal. Low-to-moderate glycemic-index foods are desirable because they enter the bloodstream slowly. Examples include bananas, dried apricots, yogurt, milk, kidney beans, apples, and pears. When eaten an hour before a long run, these foods will be digested enough to be burned for fuel, and then will continue to provide sustained energy during your run.

2.   Limit high fat foods before a marathon

High fat foods take longer to leave the stomach. Even if consumed well before a long run, these foods can linger in the stomach and cause sluggishness and nausea.

3.   Be cautious with sugary foods before exercise

Some athletes who consume sugary foods before exercise will perform better or experience no effect. For others, drinking soft drinks or sports drinks or eating candy or sugar cereals 15-120 minutes before endurance exercise may cause a drop in blood sugar that invokes fatigue and light-headedness. If you depend on a “sugar-fix” to improve performance, your best bet is to eat it five to ten minutes before your run.

4.   Allow adequate digestion time before you run your marathon

Ideally, you should allow at least three or four hours for a large meal to digest, two to three hours for a smaller meal, one to two hours for a liquid meal, and less than an hour for a small snack. However, you will need to experiment with this timing to determine what works best for you. Adjusting your training schedule to ensure adequate digestion of your pre-run meals and snacks will enhance performance.

5.   Experiment with liquid meals or snacks to fuel you for running

If you are having trouble finding pre-run foods that do not cause abdominal discomfort, try consuming liquid meals or snacks. Liquids leave the stomach much faster than solid foods, meaning they are easier to digest. However, some runners find that too much liquid sloshes in the stomach and contributes to nausea, so experimenting early in your training is recommended. There are many commercial liquid meal replacements available, or you can make your own. For example, blend 1/2 cup of vanilla yogurt, one or two peach halves, and two graham cracker squares for a fruit shake.

6.   Eat well the day before the run

If you have tried all of the above and still have not found a pre-run meal that agrees with you, plan for some extra nourishment the day before your long run. For morning runners, have an extra large bedtime snack in lieu of breakfast.


Conclusion: find your pre-run food and stick to it

Using the guidelines above, you are likely to find a pre-run food or combination of foods that is right for you. Once you figure out what works, stick with it. On the day of the race, carry those foods with you and eat only that before your race. Many runners are tempted by new performance-enhancing products they learn about at a race expo and want to try them. You may have found a great product, but you have no idea how your body is going to react. New foods carry the risk of settling poorly, causing intestinal discomfort, heartburn, or cramps. After dedicating yourself to this rigorous marathon training schedule, you have worked too hard to let anything get in the way.

For more information on what food to eat before exercise see the following article from TheDietChannel: Workout Prep: What To Eat Before Your Workout.