Eat more carbohydrates 2-3 days before race day to fuel for success.
You’ve spent months training, perfecting your pacing, testing energy gels, practising a hydration strategy, and you even have your race-day breakfast dialled in.
Every detail of your race preparation is done… except perhaps the most crucial one: carbohydrate loading.
Many athletes run, cycle, or swim without carb loading for an endurance event. The result? They run out of energy, hit the dreaded “wall,” and their performance tanks.
To give you the best possible chance at race day success for events like the marathon, you need to carb load. This is where you increase carbohydrate intake the days before racing.
This blog post explains what carb loading is for endurance athletes, how to do it, and more to help you achieve the results you know you’re capable of.
What you will learn:
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What carbohydrate loading is and why you should do it
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How to properly carb load to avoid stomach upset and other issues
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What foods to eat for the best results on race day
What is carb loading?
Carbohydrate loading, or carb loading as it’s commonly called, is when you consume more carbs before a race or endurance event.
Carbs are stored as glycogen in the muscles. Glycogen is the body’s primary fuel source for endurance activity and supports approximately 2 hours of energy for racing.
When running or cycling, for example, our glycogen stores deplete. By increasing your carb intake in the days leading up to a race or event, excess carbs are stored in the muscles and provide more fuel for endurance activity.
It’s not only carbohydrates you need to increase, either. You need to increase water and fluid intake.
It’s important to increase fluid intake during carb loading because 2.7-4g of water binds to every 1g of glycogen (stored in the form of glucose) [3]. Many people forget to increase fluid intake and do not fuel properly for endurance activity.
If you don’t increase fluid, you can’t store as much glycogen in the muscles. Consider adding electrolytes like SLT07 when carb loading/the day before an event to ensure proper hydration.
Is it good to carb load before a race?
Carb loading before an endurance race can be very beneficial. However, it does depend on the race length and duration.
Typically, events under 2 hours do not require excess carbohydrates in the lead-up to the race.
This is because your body should have enough stored energy (glycogen), provided your nutrition is in check.
For events upwards of 2 hours, carb loading ensures you have excess energy to delay fatigue and prevent you from hitting the wall or “bonking” as it’s commonly called.
If you’re doing a marathon, ultra-marathon, or ultra-cycling event, you should definitely be carb loading.
What does carb loading do?
When you eat carbohydrates, your body converts them into glucose, which is stored as glycogen in the muscles and liver.
Carb loading increases available energy for endurance athletes.
By eating more carbs 2 to 3 days before an event, your body can access more available energy to support activity.
It does not mean you won’t need to fuel during an event, like a marathon, but you start with more available energy in the form of glycogen to support your endurance efforts.
You’re less likely to bonk or hit the wall and less likely to encounter any mid-race nutrition/fuelling hiccups.
How to do proper carb loading
The week before your event, whether it's a marathon, ultra-marathon, or ultra-cycling event, start making a conscious effort to increase your carbohydrate intake.
2-3 days before the race, you can get more specific with it.
Focus on high-carbohydrate, low-fat foods. Instead of crisps, pastries, doughnuts, and sugary cereals, choose white pasta, rice cakes, bagels, and bananas.
Carb loading does not mean you can or should eat everything in sight. You should have a strategy, focusing on high-quality carb sources. Also, if you struggle to eat a lot of carbs, consider using sports drinks or other liquid carb sources.
As previously mentioned, you also need to increase your fluid intake. Your body needs water to store the excess carbs as glycogen. Without added fluid, you can’t effectively convert and store the glucose as glycogen.
Aim to get 10-12g/kg/bw a day [1].
For example, if you are 70kg, aim to consume 700-840g of carbohydrates/day for 2-3 days before the event.
When carb loading, reduce training volume and intensity. This is commonly referred to as a “taper.” By reducing activity, you not only ensure your body is repaired and ready, but less exercise also ensures your glycogen stores are elevated [2].
What foods are good for carb loading?
There are lots of great carbohydrates you can eat to carb load the days before your event. Popular options include:
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White rice
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Pasta
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Bagels or English muffins
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Sweet potatoes
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Rice noodles
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Couscous
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Sports drinks
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Porridge
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Pancakes
You can simply add an extra portion of carbs to your regular meals to increase total carb intake.
Additionally, some athletes like to eat smaller meals more frequently. Instead of three meals a day, they would eat five or even more meals with a small portion carbs at each sitting.
Do whatever works best for you so you can get enough carbs to support endurance performance.
A few extra carb loading tips
To help ensure you carb load properly before your next race or event, I’ve put together a few extra tips below:
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Practise carb loading during training to avoid stomach upset and other problems
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Limit fibre intake to avoid bloating and other digestive issues
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Try eating smaller, more frequent meals every few hours if you get full easily
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Use liquid carb sources if needed (sports drinks, fruit juice, smoothies, etc.)
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Don’t eat as much protein when carb loading (this makes you feel fuller)
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Stay hydrated and drink lots of water to ensure proper glycogen storage
If you're tackling the 26.2 mile distance, read our carb loading guide for the marathon for more specific advice.
FAQs
What is the point of carb loading?
Carb loading increases muscle glycogen stores to provide the body with more energy for prolonged endurance activity. Without carb loading, an athlete is more likely to run out of energy and “hit the wall.” By increasing carbohydrate intake, you’re essentially filling up your fuel tank.
How many days to carb load before a marathon?
You should carb load 2-3 days before a marathon to increase glycogen stores for more sustained energy on race day.
What is a good carb loading meal?
A good carb loading meal should contain more carbohydrates than usual. Pasta with marinara sauce, homemade pizza, or pancakes with syrup are great options.
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References:
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Burke, L.M., 2007. Nutrition strategies for the marathon: fuel for training and racing. Sports Medicine, 37(4), pp.344-347.
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Sherman, W.M., Costill, D.L., Fink, W.J. and Miller, J.M., 1981. Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance. International journal of sports medicine, 2(02), pp.114-118.
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Shiose, K., Yamada, Y., Motonaga, K., Sagayama, H., Higaki, Y., Tanaka, H. and Takahashi, H., 2016. Segmental extracellular and intracellular water distribution and muscle glycogen after 72-h carbohydrate loading using spectroscopic techniques. Journal of Applied Physiology, 121(1), pp.205-211.
