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

Most runners are well aware of the need to fuel during a marathon. 

There are all sorts of energy gels, sports drinks, and bars marketed to marathon runners to help fuel during the race, as well as real food options for nutrition needs during the race as well.

But what about the half marathon?

Should you take energy gels or sports drinks during a half marathon, or are these types of products only necessary in a full marathon? What should you eat during a half 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.

In this guide, we will cover: 

  • Do I Need To Fuel During A Half Marathon?
  • Why Should I Fuel for a Half Marathon?
  • Should I Fuel During a Half Marathon?
  • Half Marathon Fueling Strategy

Let’s jump in!

A person fueling during a half marathon.

Do I Need To Fuel During A Half Marathon? 

When you start training for your first half marathon, there are lots of things to consider.

For most runners, the half marathon is a big step up from their longest previous race experience because unless you’ve been lucky enough to find a relatively rare 10-miler or 15k race, you’re probably jumping up 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 the time 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. Water will suffice for hydration needs.

But what happens when you more than double the distance and step up to the half marathon? Do I need to fuel during a 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), your experience level, your body size, your preferences, and your metabolism.

Before we delve into how each of these factors may influence your personal needs in terms of 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 some sort of physical activity, your muscles need energy to do the work required to sustain the exercise.

This energy (which is 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.

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

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

The glucose can then be used by your muscle cells (or other tissue) 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.

This is because the faster you run, or the more vigorous your exercise, the higher the energy requirements of your muscles (and the more calories you burn per minute), and 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, 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 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 are burning. As mentioned, the body stores enough glycogen for about 90-120 minutes of running at marathon effort.

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 burning mostly carbohydrates during a marathon, but compared to the more intense half-marathon pace, the reliance on fat is higher.

Practically, 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 Level 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.

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.

Half Marathon Fueling Strategy

So, if you fall within the majority of runners who probably need to do some amount of 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 that pertain 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 than 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. 

Energy gels, energy bars, 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 can work well, or applesauce squeeze packets. 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.

In terms of when to eat, you need to stay ahead of your body’s needs for carbohydrates, which means start fueling about 30-45 minutes into the race.

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

If your half marathon will take upwards of 120 minutes or more, aim for 60–75 grams of carbohydrates 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 half marathon fueling is practice, practice, practice. 

Experiment and test out different fueling strategies, including the types of foods or nutrition products you take in and when you ingest them during your race.

Use your long runs to nail down your half marathon nutrition strategy.

Now that we’ve answered your question, do I need to fuel during a half marathon, let’s look at what you should eat before a half marathon. We have some great ideas for your next pre-race breakfast here.

Runners in a race.
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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