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Do I Need To Fuel During A Half Marathon? Fueling Strategy Explained

Run your best race by fueling right.

We often discuss pre-race fueling for endurance athletes, such as carb loading and hydrating with electrolytes in the days before a race and refueling after a race with a good protein and carb mix.

In addition, most runners know they need to fuel during marathons and other long-distance races, such as ultras.

There are all sorts of energy gels, sports drinks, and gummy chews marketed to marathon runners to help fuel during the race, as well as real food options such as peanut butter, nuts, and energy bars

But what about the half marathon distance?

Should you take energy gels or sports drinks like Gatorade during a half marathon, or are these products only necessary in a full marathon?

If you’ve found yourself asking, “Do I need to fuel during a half marathon?” keep reading for everything you need to know about half marathon fueling strategy on race day.

A person fueling during a half marathon.

Do I Need To Fuel During A Half Marathon? 

As a beginner, when you start training for your first half marathon, there are many things to consider.

For most runners, the half marathon is a big step up from their longest previous race experience. Unless you’ve been lucky enough to find a relatively rare 10-miler or 15-K race, you’re probably jumping to the half marathon with only a 10K under your legs.

Depending on your speed, running a 10K typically takes an hour or less, and even slower runners will not be running significantly longer than an hour from when the gun goes off until they cross the glorious finish line.

For this reason, most runners don’t have to have a 10K fueling strategy that includes in-race nutrition; they can simply focus on fueling properly before the race such as adding a few more carbs into their dinner the night before. Drinking water will suffice for hydration needs.

But what happens when you more than double the distance and step up to the half marathon?

The answer isn’t as simple as you would think, as it depends on factors such as your pace (and thus how long it takes you to finish the race), experience level, body size, preferences, and metabolism.

Before we delve into how each of these factors may influence your personal needs regarding the best half-marathon fueling strategy, let’s briefly cover why fueling during a half-marathon may be necessary.

Runners in a half marathon.

Why Should I Fuel for a Half Marathon?

Any time you run or perform physical activity, your muscles need energy to do the work required to sustain the exercise. This energy (in the form of ATP) is generated by oxidizing or burning fuel from the nutrition you’ve taken in.

The two primary forms of fuel for the muscles are carbohydrates and fats. Proteins provide some amount of energy during intense exercise, although the relative percentage is much less.

Fat is the primary fuel source for the muscles during low-intensity exercise, such as walking, yoga, or very slow jogging.

Even for the leanest runners, the body has enough stored fat to sustain several days of continuous running without consuming more calories.

Each pound of stored body fat provides about 3,500 calories of energy, so if you use a rough estimate of 100 calories per mile for the energy expenditure of running, each pound of fat can power 35 miles of running.

Therefore, you could theoretically run for several days on all of the body fat that you carry.

Runners in a half marathon.

However, here’s where fueling for running comes into play: During vigorous exercise, such as running, the muscles rely primarily on carbohydrates to produce energy.

Unlike in the case of body fat, glycogen stores are in a relatively limited supply.

Carbohydrates that you take in through your diet are converted into glycogen,1Murray, B., & Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition Reviews76(4), 243–259. https://doi.org/10.1093/nutrit/nuy001 a much larger molecule that is formed by synthesizing many simple sugar molecules together.

When you run, your muscles, brain, and heart quickly use the available blood sugar for energy, so the stored glycogen can be broken down into simple glucose molecules.

Your muscle cells (or other tissue) can then use the glucose to generate ATP to support your exercise.

The body has limited glycogen stores in the liver and skeletal muscles, and these reservoirs deplete even faster as the intensity of your exercise increases. This is because producing ATP by oxidizing fat is a much slower process than producing ATP by burning glycogen.

As a result, the faster you run, the more your muscles rely exclusively on carbohydrates for fuel rather than fats.

The more vigorous your exercise, the higher the energy requirements of your muscles (and the more calories you burn per minute).

Since oxidizing fat is a much slower process, the energy yield from burning a triglyceride (fat molecule) can’t keep pace with the energy demand of the muscles.

A person drinking a sports drink.

In other words, generating energy by burning fat is insufficient for the high demand of the muscles during high-intensity exercise.

According to the Academy of Nutrition and Dietetics,2How to Fuel Your Workout. (n.d.). Www.eatright.org. https://www.eatright.org/fitness/physical-activity/exercise-nutrition/how-to-fuel-your-workout an endurance-trained athlete can store up to 1,800 to 2,000 calories of fuel as glycogen in the muscles and liver, though smaller runners might store closer to 1,500 calories or so.

Depending on your body weight, size and running pace, this means that you might store enough glycogen to support about 90-120 minutes of running at your marathon race pace effort.

If you don’t take in additional carbohydrates during the race, you will deplete your glycogen stores and face the dreaded experience of “bonking” or “hitting the wall.”

This sensation of fatigue and a drastic slowing of your running pace is due to the fact that once you are glycogen-depleted, your muscles have to shift to burning only fat for fuel, and as discussed, this is a much slower process.

Therefore, you are physiologically forced to slow down because the muscles aren’t getting enough energy fast enough to meet their needs.

By fueling with simple carbohydrates during your race, you provide a trickle of additional glucose so that you never deplete your glycogen stores and don’t have to fall back on oxidizing fat.

However, it’s important to make the distinction that you are not burning more calories overall when running in a glycogen-depleted state; rather, the source of those calories shifts to include a greater reliance on fat rather than carbohydrates.

A person handing a runner a bottle of water.

Should I Fuel During a Half Marathon?

As you might have inferred from that explanation, most runners do indeed benefit from fueling during a half marathon with energy gels, sports drinks, or real foods high in carbohydrates.

The faster you run, the more carbohydrates you burn.

Marathon race pace is slower than half marathon race pace, which means that a greater percentage of the calories your body needs can actually be produced by burning fat.

Of course, you are still mainly burning carbohydrates during a marathon, but the reliance on fat is higher compared to the more intense half-marathon pace.

This means that your glycogen stores may only be adequate for 75-90 minutes at half-marathon pace.

Thus, if your projected half marathon finish time is above 75 minutes or so, it’s probably a good idea to fuel during the race. Most runners take much longer than 75 or even 90 minutes to finish a half marathon.

Running Level310k Times By Age And Ability – Running Level. (n.d.). Runninglevel.com. https://runninglevel.com/running-times/10k-times reports that the average half marathon finish time is 1:43:33 for men and 2:00:12 for women.

The slower you are, the more important your half marathon fueling strategy becomes as you will take more time to finish your half marathon.

Just because your running pace is slower doesn’t mean that your effort level is any less than a more competitive runner, so even very slow runners may be burning primarily glycogen during the half marathon.

Runners in a half marathon.

How Do You Fuel The Day Of A Half Marathon?

So, if you are among the majority of runners who probably need to do some in-race half-marathon fueling, what is the best half-marathon fueling strategy?

This question involves two considerations: 

  1. What should you eat during a half marathon?
  2. When should you fuel during a half marathon?

As with most things related to running, your body is unique, and what may work best for you in terms of fueling for a half marathon may look quite different from what works best for another runner.

Although sweeping generalizations for how to fuel for a half marathon can’t easily be made, here are a few tips:

In terms of what to eat, focus on simple carbohydrates. 

Running gels, energy chews, sports drinks, UCAN, and sports beans work well.

If you prefer real food, consider dried fruit like raisins, dates, pineapple, or apricots. Fresh fruit like bananas or applesauce squeeze packets can work well. Check out our list of whole-food alternatives to energy gels here

Dried fruit is an option of what do I need to fuel with during a half marathon.

When it comes to eating, the rule of thumb is to stay ahead of your body’s needs for carbohydrates, which means starting fueling at the 30-45 minute mark of the race.

For races lasting 75-90 minutes, consider consuming about 30 grams of carbohydrates per hour (120 calories), a little every 20 minutes or so.

If your half marathon race time will be 120 minutes or more, aim for 60–75 grams of carbs per hour (240-300 calories), dividing that amount into smaller doses every 15-20 minutes.

The most important thing you can do in terms of your half marathon fueling plan is practice, practice, practice.

During your half marathon training runs, experiment with and test different fueling strategies, including the types of foods or nutrition products you ingest and when you ingest them during your race.

Use your long training runs in your training plan to nail down your half-marathon nutrition strategy.

Another important thing to take into consideration is how you are going to carry along your fuelling with you on the day of the race. Will you use a water bottle or hydration pack, or are you just going to use the aid stations provided by the organization?

If so, ensure you know what type of hydration and nutrition they plan to provide and if it works with what you have been using during training.

If you are unsure how many calories you should consume to support your training, you can speak with a sports dietitian or nutritionist to guide you.

Now that we have race strategy nutrition worked out, here are some great ideas for your next pre-race meal or pre-race breakfast:

References

Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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