Do Professional Runners Carb Load for Peak Performance?

October 18, 2025 •

3 min read

According to a review in Sports Medicine, a high-carbohydrate diet can improve endurance performance by up to 3%. Yes, professional runners carb load, but their approach is highly strategic, based on the event's duration and intensity, focusing on maximizing glycogen stores to delay fatigue and sustain peak performance.

Quick Summary

Professional runners strategically increase their carbohydrate intake, or 'carb load,' in the final 1 to 3 days before endurance events exceeding 90 minutes to maximize muscle and liver glycogen stores. This process is paired with a tapering of training volume, and often involves consuming lower-fiber, higher-glycemic carbs to prevent gastrointestinal issues and ensure maximum energy reserves.

Key Points

Strategic Fueling for Endurance: Professional runners use carb loading exclusively for endurance events exceeding 90 minutes to maximize muscle glycogen stores and delay fatigue.
Modern Method vs. Classic Depletion: The modern carb-loading protocol avoids the intense depletion phase of older methods, focusing instead on increasing carbohydrate intake (8–12 g/kg/day) for 1–3 days before the event.
Focus on Digestible Carbs: During the loading phase, professionals prioritize low-fiber, easily digestible carbohydrate sources like white rice, sports drinks, and gels to prevent gastrointestinal upset.
Practice Makes Perfect: Elite athletes practice their carb-loading and in-race fueling strategies during training sessions to ensure their body tolerates the fuel and to fine-tune what works best for them.
More Than Just a Meal: Carb loading is not a single large meal; it's a strategic period of adjusting diet and tapering training volume to saturate the body's fuel tanks completely.
Proper Hydration is Crucial: Because glycogen binds to water, professional runners also increase their fluid intake during the loading period to maintain hydration and maximize glycogen storage.

The Science Behind Elite Carb Loading

Carb loading is a nutritional strategy employed by endurance athletes, including professional runners, to maximize the storage of glycogen in their muscles and liver before a major race. Glycogen is the body's primary and most readily accessible fuel source for high-intensity exercise. For events lasting longer than 90 minutes, such as a marathon, a runner's natural glycogen stores are typically insufficient, leading to fatigue or 'hitting the wall'. By following a specific carb-loading protocol, elite runners supercompensate their glycogen stores, ensuring a full fuel tank for race day.

Modern Carb-Loading Protocols for Professional Runners

The original carb-loading method developed in the 1960s involved a depletion phase, where athletes exercised intensely on a low-carb diet before a high-carb loading period. However, modern sports nutrition has largely moved away from this, as it is unnecessarily stressful on the body. Today, professional runners and sports dietitians favor a simpler, more effective approach. This typically involves a 1 to 3-day high-carb phase combined with a tapering of training volume.

During this period, carb intake increases significantly, often to 8–12 grams per kilogram of body weight per day for the 36 to 48 hours before the event. At the same time, fat and fiber intake is reduced to decrease the risk of gastrointestinal issues on race day.

Strategic Food and Fluid Choices

The types of carbohydrates consumed are just as important as the quantity. For carb loading, professionals prioritize easy-to-digest, low-fiber sources to prevent stomach discomfort and bloating. They also frequently use high-glycemic index (GI) foods to promote faster glycogen storage.

Foods to focus on: White rice, pasta, white bread, pancakes, oatmeal, sweet potatoes (peeled), bananas, and fruit juices.
Supplementing intake: To consume the large volume of carbohydrates needed, many professionals use sports drinks, energy gels, and carbohydrate-rich bars to supplement their food intake.
Hydration is key: Since every gram of glycogen stored in the body also binds to several grams of water, proper hydration is crucial during carb loading. Many athletes consume electrolyte-enhanced beverages to aid fluid retention.

Intra-Race Fueling and the Pre-Race Meal

Carb loading alone is not enough for an ultra-endurance event like a marathon. Professional runners also strategically consume carbohydrates during the race to top up their glycogen stores and maintain performance. The pre-race breakfast, consumed 1 to 4 hours before the race, serves as a final top-up of glycogen, especially liver glycogen, which is depleted overnight.

Carb-Loading vs. Daily Fueling


Feature	Carb Loading (Pre-race)	Daily Fueling (Training)
Purpose	Maximizes glycogen stores for an upcoming endurance event.	Replenishes glycogen stores after training sessions for recovery and adaptation.
Duration	1 to 3 days before a long event (typically >90 mins).	Occurs daily, adjusted based on the training load for that specific day.
Carb Source	Lower-fiber, high-GI carbs (white rice, sports drinks, gels).	Nutrient-dense, whole-food sources (whole grains, fruits, vegetables).
Carb Ratio	8–12 g/kg of body weight/day for 36–48 hours.	Varies based on activity, e.g., 5–7 g/kg for moderate training.
Fat/Fiber	Reduced to minimize GI issues.	Standard intake, critical for overall health.

Conclusion: The Professional Approach is Strategic

The simple answer to "Do professional runners carb load?" is a definitive yes, but the method is far from a simple pasta-binge the night before. Elite athletes utilize a sophisticated, science-backed approach developed over weeks of training and guided by sports nutritionists. Their strategy focuses on precise timing, carbohydrate amounts (8-12 g/kg body weight), and easily digestible food choices to ensure maximal glycogen saturation without causing digestive distress. This practice is a critical component of their race-day preparation, specifically for events lasting over 90 minutes, and is practiced during training to ensure their bodies respond well to the fuelling strategy. By tapering their training and manipulating their diet, they arrive at the start line with full energy reserves, giving them a significant physiological advantage.

For more information on the specific nutritional strategies for marathon running, explore guides from reputable sources like Sports Dietitians Australia.

Frequently Asked Questions

Carb loading is a nutritional strategy where professional runners, in the days leading up to a race, significantly increase their intake of carbohydrates while tapering their training volume to maximize muscle and liver glycogen stores.

No, carb loading is only truly necessary and beneficial for endurance events that last longer than 90 minutes. For shorter races like a 5K or 10K, a balanced daily diet provides sufficient glycogen.

Elite athletes typically begin their high-carb phase 1 to 3 days before a marathon or other long-distance event, consuming 8 to 12 grams of carbohydrates per kilogram of body weight per day.

Professional runners focus on easily digestible, lower-fiber carbohydrates like white rice, pasta, white bread, bananas, and sports drinks. This prevents stomach discomfort that can be caused by too much fiber or fat.

Yes, it can lead to a temporary weight gain of 1-2 kg. This is not fat gain, but rather the extra water the body stores along with the glycogen. For endurance athletes, this extra water aids hydration during the race.

The pre-race breakfast, eaten 1 to 4 hours before the event, is for topping up liver glycogen stores that were used overnight. It should consist of easily digestible carbs, such as a bagel with jam or oatmeal.

The evidence suggests that for optimal performance in endurance events over 90 minutes, a high-carbohydrate diet, even as a short-term strategy, is superior to a low-carb diet. However, some athletes follow 'train-low, race-high' strategies, though evidence for improved performance is mixed.