The Ultimate Guide to Carb Loading for Runners

Carb loading is a popular nutrition strategy among endurance athletes, especially marathoners, to ensure their bodies are well-fueled for race day. When combined with an effective taper strategy, your personal best may be closer than you think!

Carb loading involves increasing your intake of carbohydrates in the days leading up to a race.

The goal is to maximize the body’s glycogen stores, which act as a primary fuel source during prolonged exercise like running a marathon.

The Origins of Carb Loading

Carb loading as a strategy has been around since the 1960s when researchers noticed athletes performed better when consuming high-carb diets.

It’s now a widely accepted practice for endurance events, particularly for races lasting longer than 90 minutes, like marathons.

Here you can find some studies about carbo loading for runners.

Why Carb Loading Matters

Glycogen is the stored form of glucose, which powers your muscles during exercise.

By boosting glycogen levels, carb loading helps runners maintain energy throughout the marathon, delaying fatigue and preventing the dreaded “hitting the wall” feeling—when your glycogen reserves are fully depleted, and your body struggles to keep up.

How to Carb Load Effectively

Carb loading typically starts 2-3 days before the race.

During this period, runners shift their focus to eating more carbs and cutting back on protein and fat, as these take longer to digest and aren’t as useful for immediate energy needs.

Here’s what a solid carb-loading strategy looks like:

• Focus on Complex Carbs: Foods like whole-grain pasta, rice, quinoa, sweet potatoes, and fruits such as bananas are excellent choices. These complex carbohydrates provide long-lasting energy without spiking your blood sugar.
• Avoid Simple Sugars: While sugary snacks can give you a quick burst of energy, they often lead to crashes, which isn’t ideal for a long-distance run.
• Eat Frequently: Spread out your carb intake over multiple meals and snacks throughout the day to avoid feeling overly full or bloated.

The key is to gradually increase carbs over those 2-3 days so that your glycogen stores are fully replenished without causing digestive discomfort.

The Benefits of Carb Loading

Carb loading offers several advantages:

• Improved Performance: With increased glycogen stores, your muscles have more fuel to draw from, which can help improve your running pace and endurance.
• Prevents Energy Crashes: Carb loading reduces the likelihood of “hitting the wall” during a race.
• Faster Recovery: Post-race, your body uses glycogen stores to recover. With higher glycogen levels, you may experience less muscle soreness and fatigue.

What to Eat While Carb Loading

The best foods for carb loading are rich in complex carbohydrates. Some options include:

• Whole-grain pasta, bread, and cereals
• Brown rice and quinoa
• Sweet potatoes
• Fruits like apples, oranges, and bananas

These foods provide steady, long-lasting energy.

Avoid high-fat and high-protein foods during this time, as they can slow digestion and take up valuable space in your diet when you should be prioritizing carbs.

Looking for more carb-rich foods? In this article, we’ve shared 12 carb-rich foods to make your carb load as effective as possible!

The Day Before the Marathon

The day before your race should be your peak carb-loading day.

Focus on eating carb-rich meals and snacks while avoiding foods that could upset your stomach.

Stick with tried-and-true foods that your body handles well—now isn’t the time to experiment with new dishes!

Carb Loading on Race Day

While most of the carb loading happens in the days leading up to the marathon, it’s important to keep consuming carbs during the race itself.

Energy gels, sports drinks, or other easily digestible carbs should be consumed throughout the race, especially as you hit the later stages when glycogen stores may run low.

During the marathon, aim to consume 30-60 grams of carbs per hour to keep your glycogen levels steady.

Energy gels and sports drinks are great options here, as they’re easy to digest and quickly replenish energy.

How Much Should You Eat?

During carb loading, aim to consume 7-10 grams of carbohydrates per kilogram of your body weight each day.

For example, a 70 kg runner would need approximately 490-700 grams of carbs daily during the loading phase.

It’s important to listen to your body and adjust based on how you feel—if you’re bloated or overly full, ease off slightly.

Find out if you're eating enough to fuel your runs properly in this article.

Carb Loading Isn’t for Every Race

While carb loading is essential for marathons, it’s not always necessary for shorter races like 5Ks or 10Ks, where glycogen depletion is less likely to occur.

For my experience (and for my stomach as well), It’s better focus on eating a balanced meal before these races rather than trying to load up on carbs.

Conclusion

Carb loading can make all the difference in how you perform during a marathon.

By following a strategic plan to increase your glycogen stores, you’ll be better prepared to tackle the distance and feel strong through to the finish line.

Just remember to prioritize complex carbs, avoid simple sugars, and stay hydrated throughout the process.

With a well-executed carb-loading plan, you can cross that marathon finish line feeling strong and energized.

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