How to Fuel for Long Runs

Even with adequate training, the final 10K of a marathon can be difficult for a runner. Many runners hit the wall (or bonk), run out of fuel, and slow down considerably. While there are several strategies—like these—to make the last 10K of your marathon your best, one of the most important factors in your race-day performance is proper fueling.

Taking in carbohydrates during a marathon will give your body the energy it needs to continue running past the 20-mile mark, and all the way to the finish line. The human body can only store enough carbs in the muscles and blood to carry you through about 20 miles. After that, you'll slow down considerably and feel a lot worse as your body runs out of fuel.

In order to properly fuel on race day, it's critical to practice your race-day fueling strategy during training, and the best time to do that is during your long runs.

More: The New Rules of Marathon Nutrition

Use Long Runs as Dress Rehearsals

The long run is the most specific workout for marathon training because of its distance—often up to 22 miles for more advanced runners with lofty goals like qualifying for Boston. It's also a great preparation tool since many runners do fast-finish long runs and run some of the miles at their goal marathon pace.

These workouts simulate what you'll experience on race day, so it's important to treat them as dress rehearsals for the marathon itself.

More: 4 Marathon-Specific Long-Run Workouts

Runners typically have two questions when it comes to fueling for long runs:

  1. When should I start taking in carbohydrates during my run?
  2. How many carbs should I eat during my workout?

Even though everyone is unique and will tolerate different amounts of carbohydrates, there are some general guidelines to follow.

First, it's most advantageous to take in some calories every 30 minutes during a long run. You could drop this interval down to 20 minutes, but you may disrupt the flow of your run and affect your pacing. It's difficult to fuel when you're trying to run faster.

The more important question is how much you should eat. To truly optimize performance, it's best to eat 60 to 90 grams of carbohydrates per hour of running during a marathon—so you want to simulate this during a long run or your other marathon workouts.

For the best performance possible, 60 grams is the absolute minimum while 90 grams is the maximum. Most runners will have trouble digesting 90 grams, so that amount is only for those with an iron stomach who can tolerate this amount of food.

More: The New Rules of Marathon Nutrition: Fuel Plan

What to Eat During a Long Run

Consuming gels or blocks during your run can help you get the carbohydrates that your body needs. The standard gel or block provides about 25 grams of carbohydrates. Eating three per hour will have you in the middle of the range of 60 to 90 grams per hour of running.

Some runners prefer more natural foods such as raisins and dates. The only drawback to natural fuel choices is that you won't be able to measure exactly how many grams of carbohydrate you're ingesting. You can make a good estimate, but if you prefer to know the exact number, you may want to stick with gels.

Consuming several gels with water and a small amount of sports drink is the simplest way to get the calories and carbohydrates you need to fuel your long run, prepare for the marathon, and train your stomach.

Remember, every runner is different, so it's important to figure out which fueling options work best for you. This is why it's important to experiment during the early stages of your training, so you'll feel confident in your fueling strategy on race day.

More: 7 Mistakes to Avoid on Your Long Runs

Start treating your long runs as dress rehearsals for the marathon and you'll feel more prepared and confident on race day.

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About the Author

Jason Fitzgerald

Jason Fitzgerald is a USATF-certified running coach, 2:39 marathoner, and the founder of Strength Running. Have a question about running? Download the free Strength Running PR Guide to get 35+ answers to the most commonly asked questions about running.

Jason Fitzgerald is a USATF-certified running coach, 2:39 marathoner, and the founder of Strength Running. Have a question about running? Download the free Strength Running PR Guide to get 35+ answers to the most commonly asked questions about running.

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