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Updated: Oct 30, 2023


Carb loading is a strategic approach to fuelling that has helped many runners steer clear of hitting the wall on race day.

Carb loading isn't exclusive to runners; it benefits various endurance athletes. If you have an upcoming significant race or endurance event, it's important to grasp how to fuel optimally for the best performance.

What is Carb Loading?

Carb loading is a dietary technique employed by endurance athletes before an event. It entails increasing carbohydrate intake beyond the usual levels to prevent hitting a point of extreme fatigue during the competition. This sensation is familiar to anyone who has embarked on a long run.

Effective race nutrition extends beyond the carb loading phase and carries through after the race. Here's a comprehensive guide to marathon training nutrition to assist you in fuelling for your next event.

Carb Loading Boosts Muscle Glycogen

Glycogen serves as the body's primary energy source. It consists of a chain of glucose molecules stored in muscles and the liver. On race day, your body initially taps into glycogen for energy to power your run.

Once glycogen is depleted, the body starts burning fat. While fat is an important energy source, it's more challenging to utilise compared to glycogen. This is when you may hit the notorious "wall". It's imperative to have your glycogen stores replenished before the event, which is precisely what proper carb loading achieves.

Benefits of Carbohydrate Loading

The key advantage of carb loading is avoiding the wall. By strategically fuelling for a race, you can prolong your endurance and perform at your peak. Ultimately, this can be the difference between achieving or missing a personal record or securing a spot on the podium.

Another benefit of carb loading is its potential to aid in hydration. If you opt for high-carb beverages, such as sports drinks, you're simultaneously hydrating. Inadequate hydration can severely hinder athletic performance, potentially even more so than glycogen depletion.

Carbohydrates play a pivotal role in various aspects of fitness, including muscle building. Learn more about how your strength training relies on carbs and how to fuel for muscle growth.

Is Carb Loading Always Necessary Before a Race?

While it's never an absolute necessity, if you aim for optimal performance on race day, carb loading is highly recommended. Think of it as ensuring your fuel tank is topped off before embarking on a long journey. With a full tank, you won't have to make unnecessary pit stops.

Definitely Carb Load for Endurance Exercise and Events

While carb loading is most commonly associated with running, it's beneficial for any endurance event. For running, consider carb loading before a half marathon or marathon for optimal results. It also proves advantageous for triathlons, long-distance bike races, and any sport demanding significant endurance.

Carb Loading Isn't Necessary for Shorter Races

On average, individuals don't deplete muscle glycogen until about 90 minutes of continuous activity. Therefore, carb loading isn't required for events of shorter duration, like 5Ks or 10Ks.

How to Properly Carb Load

The conventional image of carb loading is a hefty plate of spaghetti the night before a race. However, this isn't an accurate representation. One meal won't sufficiently replenish your glycogen stores. Here's the correct approach:

- Initiate carb loading between three and six days before your event. Anything less won't be as effective, and anything longer won't yield additional benefits.

- Gradually increase carb intake each day, aiming for 70% to 90% of your total daily intake in the two or three days leading up to the race. Aim for about five grams of carbs per pound of body weight. This doesn't necessitate consuming more calories, but rather shifting your macronutrient ratios.

- Opt for healthier sources of carbs. Avoid the temptation of fuelling up on processed snacks. Instead, focus on options like potatoes, sweet potatoes, rice, pasta, bread, and whole grains.

- Refrain from monitoring your weight during this period. As you taper your training and engage in carb loading, you may experience slight water retention and a temporary increase in weight. This will naturally normalise as you return to your regular diet and exercise routine.

In addition to carb loading before the race, you'll benefit from consuming snacks during the event. Consider using race gels or blocks, along with an electrolyte drink containing carbohydrates. Replenish your energy roughly 60 to 90 minutes into the race and subsequently every 30 minutes to maintain optimal performance.

What to Avoid During Carb Loading

While carb loading is a straightforward concept, it's easy to make mistakes. Learn from the experiences of other runners and steer clear of these common missteps:

- Relying solely on a spaghetti dinner. While spaghetti can be part of your pre-race meal plan, it shouldn't be your sole carb loading strategy. You can't replenish muscle glycogen with just one meal.

- Overindulging. Consuming excessive food before a race is unnecessary and potentially harmful. A massive meal the night before might leave you feeling unwell on race day. Instead of binge-eating, distribute your carbohydrate intake over several days and throughout the day leading up to the race. Your dinner should be consistent with your regular eating habits.

- Opting for rich, heavy foods. Steer clear of pasta with heavy cream sauces as your pre-race dinner. Stick to simple, easily digestible foods that won't lead to digestive issues later on.

- Avoiding high-fibre foods. Similar to fatty foods, a diet high in fiber can upset your stomach. Choose options like white pasta, rice, or bread, and favor simple carbohydrates. Bananas are a good choice for carb loading and have lower fibre content compared to other fruits.

- Restricting alcohol intake. While beer is rich in carbs, it's not the best beverage choice when preparing for a race, especially the night before. Occasional indulgence is fine, but limit alcohol consumption in the week leading up to your race.

- Skipping breakfast. Pre-race fuel is crucial for topping off your energy stores. Don't skip breakfast, but ensure you have enough time to digest it. Opt for a small, carb-rich meal without excessive fibre, such as a bowl of cereal or oatmeal with a banana. Stick with familiar options to avoid unexpected effects on race day.

Carb loading is a well-established and effective technique for fuelling endurance events and workouts. To perform at your best, take the time to eat appropriately and load up on carbohydrates.

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