A Sport Dietitian’s Guide to Carb-Loading for Endurance Athletes

Check out Melissa’s VIDEO of a carb loading during a busy work, travel, parenting day before a hilly 20km high intensity run in Cape Breton. Carb loading requires a plan and frequent eating! 

In the world of sports, where endurance athletes push their bodies to the limit, proper nutrition can make the difference between finishing strong and hitting the wall. At East Coast Performance Nutrition, we know that fuelling your body effectively helps you maintain energy levels, enhance performance, and support optimal health.

What is Carb Loading?

Carb loading is a nutrition strategy used by endurance and ultra-endurance athletes to maximize the storage of carbohydrate (glycogen) in your muscles and liver. Muscle glycogen is the primary fuel source during endurance exercise and concentrations decline rapidly during high intensity exercise, ultimately resulting in fatigue and decreased performance.

Carb loading means eating very high amounts of carbohydrates a few days before a big event or competition lasting over 90 minutes. When you eat more carbs than your body can use immediately, they are stored as glycogen for later use. Your liver glycogen provides glucose to the brain and additional energy for your muscles. After a good night's sleep, liver glycogen is mostly depleted, so a high-carb breakfast helps restore it before training or competition. Muscle glycogen stores, however, remain intact overnight, which means the days leading up to competition are the key time to maximize your stores through carb loading.

Why is Carb Loading Important?

Think of carb loading like topping off your energy tank to delay running out of gas so you can push your limits. By eating and drinking 10 to 12 grams of carbohydrates per kilogram of body weight, such as pasta, bagels, muffins, rice, fruit, and juice, a few days before your event, your muscles can store extra glycogen, again your body’s primary fuel source for high-intensity exercise.

Your body primarily uses carbohydrates and fat for fuel. Fat fuels low-to-moderate-intensity exercise, while carbohydrates fuel high-intensity efforts. Carbs provide energy faster and in greater amounts per minute, making them the best choice for sports performance.

Carbs = Sports Car Fat = 4-door Sedan

Unfortunately, your carbohydrate stores are limited. Muscle glycogen depletion can occur within 90 minutes to 2 hours, and sometimes even sooner, when training or competing at intensities greater than 70% VO2 max. Once glycogen runs out, fatigue sets in, and your performance can suffer. 

While glycogen stores alone won’t sustain you through an entire event, making intra exercise fuelling essential, carbohydrate loading maximizes muscle glycogen reserves to delay fatigue and sustain peak performance. This strategy enhances endurance, allowing you to maintain higher intensities for longer while reducing the risk of the dreaded energy crash, or 'hitting the wall.' Research suggests that effective carb loading can improve performance by at least 3%, with potential for even greater gains.

Who Should Try Carb Loading?

Carb loading is great for endurance athletes like marathon runners, cyclists, and triathletes preparing for events lasting longer than 90 minutes or for athletes with multiple events in one day. However, any sport requiring high intensity, regardless of duration, may benefit from increased carbohydrate intake to make sure you start exercise with adequate muscle glycogen.

If your sport requires sustained hard efforts, carb loading can saturate your muscles with glycogen, giving you the fuel to keep going. It can be the key to maintaining peak performance on competition day.

Common Carb Loading Mistakes

Many athletes make mistakes when carb loading. One common error is not practicing carb loading during training and then overloading on carbs the night before an event instead of gradually increasing intake over several days. This can lead to gastrointestinal distress and impaired performance.

Another mistake is not consuming enough carbohydrates, which can lead to increased fatigue on competition day and poor performance. Carb loading can be challenging with whole foods alone, so incorporating liquid carbs like juice and chocolate milk can help meet carbohydrate needs. Melissa always opts for chocolate milk and gingerale before big training days or competition >90 mins. 

Practicing fuelling strategies during training can help build tolerance and prevent gastrointestinal   issues on event day and enhance fuelling confidence before, and during important competition. Different sports drinks, gels, endurance powders, and carbohydrate blends work better for some athletes than others, depending on individual preferences, digestive tolerance, and sport-specific needs. Experimenting during training and working with a sports dietitian is key to determining your individual fuelling and fluid plan.

When to Start Carb Loading

Carb loading with 10 to 12 grams of carbohydrates per kilogram of body weight per day should begin 1 to 3 days before competition. If 10-12 g/kg/day seems too daunting, a more moderate intake of 8 g/kg over a longer period while tapering from training can still get the job done! 

For perspective, Tour de France athletes consume up to 18 g/kg/day before and during key race stages!! Practicing your fuelling strategies during training helps build confidence in your nutrition plan.

How much is 10-12g/kg exactly?

Here is an example of a 60kg athlete who is prone to gastrointestinal issues. 

Carb Loading Meal Plan: Before the Event

Choose lower fibre carbohydrate options like bagels, juices, muffins, white rice, potatoes, and white pasta to reduce digestive issues. Non-starchy vegetables aren’t necessary while carb-loading, as they can displace carbohydrate intake and contribute to gut residue. Low fibre fruits like bananas, applesauce, and fruit juices are usually well tolerated.

Protein intake should be 1.2 to 1.6 g/kg/day to prevent muscle protein breakdown. Include lean protein sources at meal time such as skinless poultry, white fish, low-fat dairy, soy protein, protein powders, and eggs to aid with satiety and stimulate muscle protein synthesis, but do not over consume protein the day before an event as it can displace your appetite for carbohydrates! A carbohydrate rich nighttime snack may also help meet increased carbohydrate requirements, and liquid carbohydrates like chocolate milk can make it easier to hit daily carbohydrate targets without feeling too full.

Day of the Event

Eat a pre-event meal 1 to 4 hours before competition, with 1 to 4 grams of carbohydrates per kilogram of body weight. Melissa’s usual recommendation is 2g/kg of carbs 2 hours before the event, as practiced during training. Keep choices familiar! 

For a 60kg athlete this could be a white bagel with 2 tbsp of jam and banana = 120g of carbs. 

An additional carbohydrate gel, sports drink, or banana after warming up can "top off the tank.” 

During events lasting 1 to 2 hours, aim for 60 grams of carbohydrates per hour. For events over 2 hours, 90 grams per hour can help maintain stable blood glucose levels and prevent glycogen depletion. If you are a well trained athlete who continuously exposes your gut to high carbohydrate loads, then 120g of carbs per hour for high intensity ultra endurance events lasting >2.5hrs may be recommended.

Post-Event Recovery

To optimize recovery, consume 1 to 1.5 grams of carbohydrates per kilogram of body weight and 0.4 grams of protein per kilogram, with 2-3g of amino acid leucine. Replacing lost fluids and electrolytes is also crucial for hydration and muscle recovery.

Creating a well-thought-out carb-loading plan can help you maximize performance and achieve your endurance goals. With the right nutrition strategy, you can optimize glycogen stores, boost endurance, and cross that finish line feeling strong and confident.

Book with East Coast Performance Nutrition Dietitian's today to unlock your full performance potential!