Eating for Endurance: Fuelling for a ½ Marathon and Beyond

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Too often I see people spend months training for a race, and then on race day they have no plan for how they intend to fuel themselves for the event. Don’t leave your performance to chance. Developing a sound nutrition plan will help you train well and feel your best on race day.

Simple changes can often make a big difference. Follow these 3 sports nutrition strategies to get informed so you can feel your best during training and on race day:

1) Hydrate (and then hydrate some more)

Exercising generates heat and your body’s way of regulating this is by sweating, which causes you to lose water and sodium. Human bodies are about 50-70% water depending on body composition (muscle contains much more water than fat) and losing even 2% of your total body water during exercise can have a big impact on how you feel and perform.

Specifically, getting dehydrated impacts your ability to run in the following ways:

  • Increased heart rate – this has big implications if you use heart rate training

  • Reduced ability to sweat (and get rid of heat)

  • Increased perception of effort (it feels harder to maintain the same pace)

How to Stay Hydrated?

Drink enough fluids so that your urine is the colour of lemonade. If you know you’re going to be heading out for a run and the forecast is calling for warm weather, try to drink 2-4 cups in the hours before you go.

Fortunately, fluids can come from a variety of sources and not just water. Milk, juice and even tea and coffee can all contribute to your fluid intake (though ideally caffeinated drinks shouldn’t be your only source of fluids).

Hydrating On the Run

For runs lasting less than an hour and when conditions are not overly hot or humid, being well hydrated before heading out is usually sufficient.

As the weather warms up and your distance increases, taking in fluids becomes more important for preventing dehydration. This is where on-the-go fluid options such as a hydration pack, belt or hand-held water bottle become important. Choosing what type of wearable hydration is right for you is highly individual and can take a bit of trial and error to sort out. While many people find it to be an adjustment to carry fluids, over time it can become second nature to pack fluids to the point that you feel like something is missing if you don’t bring fluids along.

Taking in carbs on a longer event can mean the difference between finishing strong and being unable to maintain your pace (or worse, bonking) in the latter half of a longer event.

What does this mean for race day? Pay extra attention to drinking fluids in the days prior to your race and aim for 2-4 cups of water in the hours before the start. Find out what will be offered at aid stations on the course (is it new or have you tried it before?) and pack fluids for longer events when you can.

2) Gut Training

While the term gut training may make you think about doing sit-ups, it actually has to do with digestion. In the same way that you train your muscles and cardiovascular system to adapt to your workouts to get stronger and faster, you can train your digestive system to tolerate different foods and fluids while exercising.

For runners training for events lasting more than 60-90 minutes, this is particularly important. Stored energy in muscles (called glycogen) typically starts running out around 45 minutes depending on your intensity level. What’s the solution? Carbs! There is strong evidence that for endurance events lasting longer than 60-90 minutes that taking in carbohydrate foods will make it possible for you to maintain your pace and intensity for longer than if you did not take anything in. This can be the difference between finishing strong and being unable to maintain your pace (or worse, bonking) in the latter half of a longer event.

How Much?

While the recommended amount of carbohydrate to consume during longer runs depends on the length of the event and the intensity that you are running it, best practice guidelines suggest aiming for 30 g of carbohydrate per hour at minimum after the first hour. For events lasting longer than 2-3 hours the recommendations increase.

What does 30 g of carbohydrate look like:

  • 2 Nuun tablets and 1 Gu Gel

  • 350 ml Gatorade and 10 Fruit Source Bites (BTW this is what I used in my recent half marathon)

  • 4 Cliff Bloks

Olympian marathoner (and fellow Registered Dietitian) Krista Duchene has been interviewed about her race nutrition. She consumes more than 100g of carbohydrates per hour during a marathon. That is a LOT of carbs! I have no doubt she had to train her body to tolerate that amount of food running at her incredibly fast race pace.

Many people tell me that they have trouble tolerating carbs on the run, especially at higher intensities. Cramping, bloating, gas and even bathroom stops are common concerns. This is normal, and even expected if you are not in the habit of taking in carbs for longer distance events. With practice, however, you can train your gut to tolerate carbs so they can work for you, not against you.

Gut Training: Where to start?

My rule of thumb is start low and go slow. I usually suggest that runners start with a sports drink because it fulfills your body’s need for both fluid and carbohydrates at the same time. In the same way that you may build your distance when training for a longer event, you can continue to add in carbohydrates slowly so your gut has time to adjust.

Gut training is a very individual process, especially for runners who have had difficulty tolerating fluid and carbs on the run in the past. For customized support be sure to consult with a Registered Dietitian.

What does this mean for race day? Your race day nutrition plan should include your goal amount and types of carbohydrate foods that you know you have trained your body to tolerate. Find out what is offered on the course and if it’s not something you tried and know you tolerate, pack your own (no surprises!).

3) Time your Nutrition Right

When it comes to eating before a run, timing is almost as important as what you eat.

As I’ve said in previous posts, food is only helping you run faster when it’s digested and absorbed. For meals, this process can take a few hours meaning that it’s really what you eat for lunch that is fuelling your after work run (not what you eat an hour before).

Foods high in fat, fibre, and protein take longer to digest than foods lower in these nutrients. The closer you get to the time of your run, the more important it becomes to eat food that you can digest and absorb quickly.

What does this mean for race day? Eat breakfast no later than 3 hours before the start. Yes, this might mean getting up earlier than you had planned to. Take this extra time to stretch and get organized for the race, or even head back to bed for a bit after. Having a smaller snack shortly before race start can also help ensure you get some extra energy without filling up. Great choices are a few sips of juice or ½ a banana.

The Take Away

If there is one thing that you take away from this blog post let it be this: in the same way that you train your muscles and cardiovascular system to prepare for a race, you can train your body to to tolerate the fluids and fuel it needs to perform your best.

Is there a strategy that is simplest for you to adopt? Which one will you try first? I’d love to hear your comments.

Happy Running,



1. American College of Sports Medicine, Academy of Nutrition and Dietetics, Dietitians of Canada (2015). Joint Position Statement on Nutrition and Athletic Performance, Medicine & Science in Sport and Exercise.

2. Jeukendrup, A., Carter, J., & Maughan, R. (2015). Competition fluid and fuel. In Burke, L. & Deakin, V. (5th Eds), Clinical Sports Nutrition (pp377 – 419). Sydney, NSW: McGraw-Hill.

3. Kuikman, M. (2018). 5 Nutrition Lessons from Krista Duchenes 2018 STWM Performance. Retrieved May 29, 2019 from