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Cross Training For Runners

How To Run A Marathon Or Half-Marathon On A Low-Carb Diet?

6 Mins read

From elementary school, they teach kids that carbohydrates help the body get the needed energy to function.

However, it seems to go against all known facts that an athlete, precisely a marathon runner, could accomplish the race without carb loading.

But is it possible to complete a whole 26.2 mile-race (42.1 kilometres) while on a low-carb diet? Or even, half of it?

This discussion explores how to run a marathon or half-marathon on a low-carb diet. Keep reading.


According to experts, including dietitians, it appears possible to live on a low-carb diet and make it in the marathon.

Low-carb options for meal replacements go a long way in injecting your body with the needed energy in readiness for the monumental task ahead.

While the essence of writing this post is to show you it‘s possible to run a half-marathon or a full marathon on low-carb, it’s also important to point out a few things.

A low-carb diet alone will not and doesn’t guarantee you the best performance on the track.

Your coach or trainer will tell you that you need a lot more.

Additional Resource – Here’s the full guide to how long is a marathon.

The Role of Carbs in Exercise

Undoubtedly, carbohydrates are perhaps the quickest and simplest in fueling your body with the needed energy during exercise.

Because of the energy demands, our bodies require carbs or energy-providing foods to supply the needed energy.

Marathon running and cycling, among other aerobic activities that require oxygen, typically demand many carbohydrates.

Speaking of running on low-carb, a sports magazine, The European Journal of Sport Science, observes that intake of carbohydrates enhances an athlete’s performance even if used as a mouth-rinse.

Marathoners will do better to maintain an hourly intake of 30-60 grams of carbs.

Some dietitians argue that tedious events that take longer than 2 hours, such as marathons, require up to 90 grams of carbs per hour.

Thankfully, experts agree that it’s now possible for marathoners to make it to the tape with just 60 grams of carbs per hour every day.

Additional resource  – Keto diet food list

Cutting Carbs During Endurance Training

For many years, athletes, including marathon runners, have thought that increasing carbohydrate intake a few days before a big race would help them inject energy into their reserves.

In their view, portions of pasta, rice, pieces of bread, and food rich in carbs were a big deal.

They thought (mistakenly anyway) that eating lots of such foods a few hours before a big race would help them have more endurance, increase their energy and finish on top of the race.

The truth is;

Cutting on carbs days before the race may help the body adapt well and remain more energetic in readiness for the race.

Here is the fact!

When you train your body to burn fats, you’ll lose the fats. But, the good thing is your body becomes less independent of carbs for its energy and glucose from sugar.

In the end, you’re likely to go for hours without needing food because your body is trained to use energy from its stores.

It doesn’t need to depend on foreign supplements such as glucose, sugar, or even energy drinks.

With fewer cravings, balanced energy, and a trained body, you’re likely to run even longer than the 42.1 kilometres we are talking about.

In fact, Mirna Valerio, an experienced American marathoner, and author observes that a fat-adapted sprinter knows that when carbs are scarce, the body can still burn fat.

Additional resource – How to nail your sub 4 hour marathon pace

Does Distance Running Require Any Carbs?

As mentioned earlier, the recommended carb intake for long-distance runners is between 30 to 60 grams per hour.

You can add or reduce this amount depending on your aim.

For workouts that are less than 60 minutes, the goal weight is 150 pounds. Then, there’s no harm in eating between 100 to 150 grams of carbs each day.

Indeed, some experts have devised a daily diet for a fat-adapted runner.

According to Hundt, a long-distance runner interested in remaining hungry-free during the training and actual marathon will follow this daily dietary and workout routine sample.

Morning workout routine

The morning workout routine is typically a 60-minute morning run

For breakfast, you can have the following;

  • Frozen butternut squash,
  • Frozen cauliflower
  • A half sweet potato
  • 30g of protein powder (or you can substitute it with 3-egg omelettes) smoothies for post-workout

Here is what your mid-day meal will look like;

  • Grilled chicken
  • Broccoli
  • Tomatoes
  • Cabbage
  • Avocado
  • Mixed green salad (big enough) and dress the meal using lemon juice and olive oil.

Further, you can incorporate an afternoon snack only if you’re hungry. For this, choose the following vegetable smoothies;

  • Three Turkey slices sandwiched with a half avocado
  • Raw Rev Glo Bar or Epic bar.

You can have roasted salmon or any other fish as you wrap up the day. Top it up with grilled asparagus.

Additional Resource – Why Do I sweat too much while running?

Why A Marathoner Needs Carbs

When speaking on low-carb running, Chris MacDonald of Women’s Running notes that the liver and muscles are where the human body gets the energy to function.

Notably, these stores are conveniently located, and upon depletion, the body looks for alternative energy sources.

According to the expert, dozens of low-carb diets vary in terms of the required amount of carbohydrates.

MacDonald says that for runners who intend to thrive on a low-carb diet, the best approach would be to maintain a ‘timed’ low-carb diet.

That means a runner should endeavor to eat adequate amounts of carbs at specific times of the day or period. It can be before, during, and immediately after the workout.

However, it’d be risky to eat foods rich in carbohydrates during other times of the day.

To replace a low-carb diet, a runner should eat foods rich in proteins. Such foods include protein powders, seeds, nuts, fish, soy, eggs, meat, and vegetables.

By following this routine, the expert remarks that your body will burn fat more during training, enabling it to heal properly after a challenging workout.

Additional Resource – Creatine For Runners

Benefits of a Low-Carb Diet for Long-Distance Running

You are wrong if you thought you’d only achieve in the marathon while on a complete carb diet.

Here are some benefits of maintaining a low-carb diet if you want to become a successful marathoner;

1.       Improved Fat Adaptation

Short-distance runners use a lot of energy from their glycogen reserves for a short period. However, running out of fuel for marathon runners, sometimes for a long time, is the norm.

When we push our bodies hard, sometimes far to the corner, we drain all the energy reserves.

After draining the glycogen reserves but yet to complete the race, your body turns to another reserve known as fats.

Therefore, when you’re on a low-carb diet, you teach your body how to survive on the two energy sources.

The beauty of this creative process is the body knows when it is the right time to get the energy needed to complete the race.

Additional resource – Can you run a marathon on keto

2.       Improved Sleep and Energy Balance

If you’ve tried a low-carb diet, you know that the first few days were hell. Your body starves a lot as it tries to adapt to the new style.

As you may already know, if you eat many carbohydrates during the day, you’re bound to stay alert and even awake for the better part of the night.

With a low-carb diet, you sleep much faster than if you took many carbs during the day.

Sleeping with a stomach full of carbs leads to sweating and restlessness. If you hit the gym in the morning, you’ll feel hungry and unproductive.

Sound sleep following intake of low-carbohydrate foods leads to enjoying a restful night.

Eventually, you’ll feel fresh and ready for exercise when you wake up the following morning.

When you hit the gym, your body will endure more because it still has reserved energy.

Additional resource – How long is a half marathon

3.       Body Recomposition After Fat Loss

Your body uses a lot of energy and burns a staggering amount of fat during training and the actual marathon.

However, many athletes often worry about what will happen to their bodies during and after the marathon.

Even though the body may lose shape, it doesn’t mean you will lose your muscle. The good thing is that your physical stamina will always remain and sometimes be visible.

After your body has burnt all the fats and the energy from its glycogen reserve, there comes recovery time. You need to feed on proteins during this time when out or in between the race.

Including proteins in your daily diet will keep your muscle and maintain body strength, which is essential for future races.

Additional resource – Guide to Marathon Des Sables


Gone are the days when traditional marathon running emphasized feeding on carbohydrates during the entire training period. Now, your body can endure the tedious long-day workouts and perform outstandingly during the race.

The important thing is to know when to introduce a low-carb diet and when to bring in foods rich in proteins for faster body recovery. Otherwise, do your workouts, and eat high-carb foods before, during, and immediately after. Still, retract to low-carb foods during the rest of the time.

If that is your dream goal, you will be surprised to hit the tape in less than 2 hours.

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