How long before a race should I start carb loading?

January 5, 2026 •

3 min read

According to sports nutrition experts, effective carb loading requires more than just a large pasta dinner the night before a race. The modern approach recommends increasing carbohydrate intake over a period of 2 to 3 days to maximize muscle glycogen stores before an endurance event. This strategic timing is key to ensuring you have the fuel needed to perform your best.

Quick Summary

The ideal carb-loading period for endurance events is 2 to 3 days before the race. This allows for the gradual increase of carbohydrate intake to maximize muscle glycogen stores. Athletes should focus on consuming familiar, low-fiber, high-carb foods while reducing fat and protein.

Key Points

Timing: Begin carb loading 48 to 72 hours (2-3 days) before your endurance race to effectively top off your glycogen stores.
Food Focus: During the loading phase, prioritize easy-to-digest, low-fiber carbohydrates like white rice, pasta, and bananas, and reduce intake of high-fat foods and excessive protein.
Gradual Increase: Spread your carbohydrate intake across several meals and snacks each day to avoid bloating and discomfort from one single, large meal.
Calculation: Aim for 8-12 grams of carbohydrate per kilogram of body weight per day during the 2-3 day loading phase.
Hydration: Increase your fluid intake during the carb-loading period, as water is essential for glycogen storage and helps maintain hydration levels for the race.
Practice: Always test your carb-loading strategy during your long training runs to identify which foods work best for your digestive system on race day.
Modern Method: The outdated depletion-and-loading method is no longer recommended. The modern approach focuses only on the loading phase alongside your taper.

Timing is Everything: The Modern Approach to Carb Loading

For endurance athletes, arriving at the start line with fully stocked glycogen reserves is crucial for a strong performance. The practice of carb loading has evolved from the older, more extreme depletion-and-loading methods to a simpler, more effective strategy focusing on the final 2 to 3 days before an event. This approach, combined with tapering, allows your muscles to maximize glycogen storage without the severe physiological stress of a depletion phase.

Why You Need More Than One Meal

The image of an athlete devouring a massive plate of spaghetti the night before a race is a classic stereotype, but it is not an effective carb-loading strategy. Your body can only absorb and store a certain amount of glycogen at a time. Trying to cram all the carbohydrates into a single meal can lead to digestive discomfort, bloating, and poor sleep, which are counterproductive to peak performance. A staggered approach over 48 to 72 hours ensures a gradual and complete top-up of your energy stores.

What to Eat During the Carb-Loading Period

During your 2-to-3-day carb-loading phase, the goal is to shift your macronutrient ratio to favor carbohydrates while reducing fats and fiber. This helps avoid gastrointestinal issues that can arise from unfamiliar or difficult-to-digest foods.

Food Choices for Effective Carb Loading:

Easy-to-digest starches: White rice, white pasta, plain bagels, potatoes without the skin.
Liquid carbs: Sports drinks, fruit juices, or even soft drinks can help meet your high carbohydrate targets, especially if you feel full from solid foods.
Fruits: Bananas are an excellent low-fiber choice. Peeled fruits like apples and pears can also work well.
Moderate protein: Include lean protein sources like grilled chicken or tuna in your meals, but keep the portions smaller than usual to prioritize carb intake.
Practice in training: To avoid race-day surprises, test your carb-loading meals before your longest training runs. This helps you understand what works best for your digestive system.

How to Calculate Your Carb Intake

Recommended carbohydrate intake during the loading phase varies but typically falls between 8 and 12 grams per kilogram of body weight per day. For many athletes, this can feel like a large volume of food, which is why spreading it out over several smaller, more frequent meals is beneficial.

Example for a 70kg athlete: Aim for 560 to 840 grams of carbohydrates per day for 2-3 days before the race.

Carb-Loading Comparison: Classic vs. Modern Approach


Feature	Classic Method (1960s)	Modern Method (2-3 Days)
Depletion Phase	Required—3-4 days of intense training and very low carbs.	Unnecessary—Modern research shows this is not needed and causes undue stress.
Loading Duration	3-4 days.	2-3 days before the event.
Recommended Intake	High carb intake after depletion phase.	8–12 g/kg of body weight per day.
Focus Foods	High-carb focus after depletion.	Familiar, easy-to-digest, low-fiber carbs.
Side Effects	Increased risk of gastrointestinal distress and physiological stress.	Reduced risk of GI issues; temporary water weight gain is normal.

Conclusion: Start Loading 48 to 72 Hours Out

The optimal strategy is to begin your carb-loading phase approximately 48 to 72 hours before your race. This window provides enough time to progressively increase your glycogen stores without the risks associated with older, more extreme methods. By focusing on a higher proportion of carbohydrates in your meals, choosing easy-to-digest foods, and staying well-hydrated, you will maximize your fuel reserves for race day. Remember to practice this routine during training to discover what specific foods and timings work best for your body, ensuring you arrive at the start line feeling energized and ready to compete.

The Importance of Hydration During Carb Loading

As you increase your carbohydrate intake, remember that your body stores water with glycogen. For every gram of stored carbohydrate, your body stores approximately 3 grams of water. This means proper hydration is just as important as your food choices during the loading period. Staying hydrated will help facilitate the storage of glycogen and also ensures you start the race well-hydrated, a critical factor for endurance performance. Make sure to increase your fluid intake along with your carbs, including water and electrolyte-rich drinks. For more in-depth nutritional guidance, consider visiting the official website of the American College of Sports Medicine, a respected authority on exercise science and nutrition (https://www.acsm.org/docs/default-source/files-for-resource-library/carb-loading.pdf).

Frequently Asked Questions

No, carb loading is most beneficial for endurance events lasting longer than 90 minutes, such as a half-marathon, marathon, or triathlon. For shorter races like a 5K or 10K, your normal, balanced diet is typically sufficient.

A general guideline is to consume 8-12 grams of carbohydrates per kilogram of your body weight per day during the carb-loading period. Athletes on the lower end of this range (8 g/kg) may benefit from a 3-day load, while those aiming for higher intake can use a 2-day period.

Eating a large, carb-heavy meal the night before is not effective for maximizing glycogen stores and can cause digestive issues. It's far better to spread your carb intake over 2-3 days, eating smaller, more frequent meals to allow your body to store the energy properly.

It is best to reduce your fiber intake during the 2-3 day loading period. High-fiber foods can cause gastrointestinal distress, bloating, and cramps during a race. Opt for low-fiber options like white rice, white bread, and peeled fruits.

It is normal to experience some temporary weight gain and bloating during carb loading. This is because your body stores water along with glycogen, which is a sign that your energy reserves are building. The extra fluid also helps with hydration during the race.

Focus on familiar, easily digestible carbohydrates that are low in fiber and fat. Good choices include rice, pasta, bagels, oats, potatoes, and bananas. You can also supplement with sports drinks or fruit juice to hit your carb targets.

Yes, a carbohydrate-rich breakfast 2-3 hours before your race is essential for topping off your liver's glycogen stores, which are depleted overnight. Stick to foods you've practiced with and know you can tolerate well.