Marathon training nutrition: How to fuel your body during marathon training


Romain Chevalier is a certified health and performance coach, pilates instructor and personal trainer.

A highly decorated athlete, he is ranked among the top 10 triathletes in Thailand.

He is based in Hua Hin and can help you become the best version of yourself.

Connect with Romain on Facebook and start your journey to a better you @HealthCoachRomain

Continuing his monthly health and fitness feature for Hua Hin Today, Romain shares some nutrition tips for marathon runners. 

The Hua Hin Marathon is set to take place in May and ahead of the big day, here are some tips on the spicy topic of nutrition. 

When it comes to nutrition, every runner has his own approach.

In addition, there is so much information out there that it is very difficult to know exactly what is best.

Proper nutrition can help fuel your body during training, aid in recovery, and optimize your performance on race day.

Succeeding or failing at nutrition can be a defining factor for having a good day or a bad day on race day. In fact, the famous saying “hitting the wall” is directly connected to nutrition on race day.

Hitting the wall is a simple saying for reaching a low (too low) level of glycogen. In very simple terms, the level of sugar in your blood went down too much, and in order to self-protect, your brain will shut down unnecessary activities like running. Because your brain needs a certain level of blood sugar to keep functioning properly.

First of all, let’s take a step back and look at a few fundamentals when it comes to nutrition for marathon runners.

  • What fuel does your body need to run a marathon?

Specifically, in Thailand, temperature and humidity are high so your body is working hard to self-regulate which in turn means you will burn a lot of calories.

To run a marathon, you will roughly burn from 3000 to 4500 calories, depending on how long you will take to complete the distance, how heavy you are, how hot it is etc. The longer, the heavier and the hotter it is, the more you will burn calories.

Most of those calories will come down from your glycogen store and a little from your fat store. In simple terms, the fitter you are, the better you can use fat to fuel your run, don’t get it wrong, you will always need glycogen as the main fuel source to run.

Here is the trick, our glycogen store (muscle and liver) is only 1800-2000 calories.

So how can we run a marathon without hitting the wall?

That’s where nutrition during the event becomes very important. Here are my tips:

  • Get a gel (100 calories) every 30min – open it  and take the time to sip through it, take 5-10min to get it through, it will be easier on your digestive system.
  • Unless you are aiming for a very fast time (sub3h), make sure to walk through a couple of water stations and drink sports drinks, let the heart rate come down and properly hydrate.
  • Whatever nutrition strategy you choose in the race, make sure to have tried it in training, every run you take which is longer than 70-80min is a good occasion to practice your nutrition.
  • What does your body need to recover optimally from running?

Protein and carbohydrates are absolutely essential.

Running burns quite a lot of calories (600-800cals / hour) and in order to properly recover you need to restore your fuel of glycogen with carbohydrates and protein to let your muscle repair and get stronger for the next session.

Another very important parameter of recovery is when you eat. Ideally, it is straight after the session.

My tips:

  • Get a protein shake straight after the session.
  • Make sure you have something ready to eat for when you come back from your run. I personally love a slice of bread with peanut butter, it’s good, easy and can be consumed quickly. Depending on how long the run was, eat 2-3 slices or more before getting a proper meal. 
  • Hydrate with water and electrolytes during and straight after your run but also during the day.

Another big mistake I see from people training for marathons is to skip eating after they train. By doing this they are failing to replenish the glycogen stores which in turn leads the body to start burning muscle. This is something that should be avoided. 

Taking a closer look at hydration

Failing to properly hydrate is one of the main reasons why someone would hit the wall and not them to not finish a marathon. A lack of proper hydration can not only affect performance but can cause muscle cramps.

But it can all be avoided by understanding how to hydrate properly. Obviously, with the high humidity and the heat, we sweat a lot more than in a cooler environment.

But what is sweat?

Sweat is mostly water and sodium (salt) and a few other minerals such as potassium, calcium, and magnesium. That’s why drinking only water might not be sufficient. 

Instead, you should also consume sports drinks and gels which often contain extra minerals.

My tips:

  • Weigh in before and after a long run, measure your hydration during the run and understand what your sweat rate is, eg 1.5L/hour. It is really hard to replenish all the water lost during a marathon but you should drink enough to not cramp up or hit the wall. Aim to not lose more than 6-8% of your total body weight.
  • Coconut water, lime and himalayan salt is a nice natural electrolyte that you can use during and after your run.

If you tend to have cramps, you might take a salt stick before the race and consume 1 every hour. Try it on your long training run, aim for 1g of sodium per hour.

Carb loading and what to eat pre-race

Carb loading is the idea of filling up your glycogen store. If you prepare for a marathon, you should reduce your training load one to two weeks ahead of the event. If you keep eating as usual, your glycogen store will naturally fill up so you should not overeat carbs a week before.

My tips:

  • Eat as usual during the week. Have a solid lunch with carbs (rice, pasta) the day before the race but not excessively. The last evening before the race, have a little bit of carbs again, avoid fibers and spicy food.
  • Marathons in Thailand usually start 2-4am in the morning so have your dinner around 6pm.
  • Wake up about 2 hours before the race and have a quick breakfast. My personal favorite is:
    • 1 or 2 slices of bread, peanut butter, black coffee and orange juice.
    • Sport drinks that I sip through until the race starts.
  • Practice the morning breakfast in training.

I hope these tips will help you to crush your upcoming marathon. Remember, when it comes to nutrition, always practice during training first. Don’t try anything new on race day. 

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