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Writer's picturePhilip Gonçalves

Mastering Carb Loading for Optimal Endurance Performance

Carbohydrate loading is a tried-and-tested strategy employed by endurance athletes to enhance their glycogen stores and maximise performance during long-distance events. By effectively fuelling your muscles with carbohydrates, you can boost endurance, delay fatigue, and achieve your best performance. In this guide, we will delve into the dos and don'ts of carb loading, providing guidelines that anyone can implement to optimise their performance during endurance events.

The Science Behind Carb Loading:

Glycogen is the storage form of carbohydrates in our muscles and liver. During exercise, especially prolonged endurance activities, glycogen serves as a critical fuel source to sustain energy levels. However, the body's glycogen stores are limited, and they can become depleted after extended periods of exercise. Carb loading aims to increase these glycogen stores by consuming higher amounts of carbohydrates. By doing so, athletes can enhance their endurance and delay the onset of fatigue during long-distance events.


It's important to note that carb loading is typically recommended for endurance events lasting longer than 90 minutes, where glycogen depletion becomes a significant factor. For shorter races or activities, normal carbohydrate intake and glycogen stores are usually sufficient.

Benefits of Carb Loading:

  1. Maximising Glycogen Stores: By increasing carbohydrate intake, athletes can top up their glycogen stores beyond normal levels. This provides a greater fuel reserve for the muscles to rely on during the race, allowing them to perform at a higher intensity for a longer duration.

  2. Prolonged Endurance: With larger glycogen stores, athletes can sustain their energy levels for a more extended period before experiencing fatigue. This helps to delay the onset of the "bonking" or "hitting the wall" sensation, which occurs when glycogen levels are depleted, leading to a significant decline in performance.

  3. Enhanced Performance: When glycogen stores are plentiful, athletes can maintain a faster pace and output more power throughout the race. Having ample carbohydrates available as an energy source enables the body to perform optimally, resulting in improved race times and overall performance.

  4. Mental Focus: Adequate carbohydrate availability has been shown to enhance cognitive function and reduce mental fatigue during prolonged exercise. Carb loading helps athletes stay mentally sharp and focused, enabling them to make better decisions and maintain their race strategy.


How To Carb Load

Begin carb loading 2-3 days prior to your race to allow ample time for glycogen stores to replenish.


To calculate your carbohydrate needs during a carb load, you can use your body weight as a starting point. Here's a step-by-step guide:


- Determine your body weight: Weigh yourself in kilograms (kg). If you are using pounds (lbs), divide your weight by 2.2 to convert it to kilograms.


- Determine the recommended carbohydrate intake range: During a carb load, the general guideline is to consume 7-10 grams of carbohydrates per kilogram of body weight. This range allows for individual variation and specific training demands. Here's how to calculate the range:

  • Multiply your body weight in kilograms by 7 (lower end of the range) and by 10 (upper end of the range). For example, if you weigh 70 kg, the calculation would be: Lower end: 70 kg x 7 g/kg = 490 grams of carbohydrates Upper end: 70 kg x 10 g/kg = 700 grams of carbohydrates

- Determine your carbohydrate intake within the range: Depending on your training volume, intensity, and personal preferences, you can select a target carbohydrate intake within the recommended range. Consider factors such as your tolerance to higher carbohydrate intake, previous experiences with carb loading, and individual response to different levels of carbohydrate intake.


- Distribute carbohydrate intake throughout the day: To optimise glycogen replenishment, divide your chosen carbohydrate intake into multiple meals or snacks throughout the day. Aim for 4-6 smaller meals/snacks rather than a few large meals. This approach helps with better digestion, absorption, and utilisation of carbohydrates.


Remember, these calculations provide a general starting point. Individual variations and specific training goals may require adjustments. It's also important to listen to your body and make adjustments based on how you feel and perform during the carb load.

Foods to Avoid and Why:


A) Fatty foods

  1. Slower Digestion: Fatty foods, especially those high in saturated fat, take longer to digest compared to carbohydrates. This can slow down the digestion process, leading to delayed nutrient absorption and potentially causing discomfort or gastrointestinal issues during exercise.

  2. Reduced Carbohydrate Absorption: Fatty foods can interfere with the absorption and utilisation of carbohydrates. When consumed together, fat can slow down the emptying of the stomach and the absorption of nutrients, including carbohydrates. This can hinder the efficient delivery of carbohydrates to the muscles, where they are needed for energy production.

  3. Higher Caloric Density: Fatty foods tend to be more calorically dense compared to carbohydrates. While both provide energy, fat provides more than twice the calories per gram than carbohydrates. When focusing on carb loading, it is important to prioritise carbohydrate-rich foods to ensure an adequate intake of the primary fuel source for endurance exercise.

  4. Weight and Satiation: Fatty foods can contribute to a feeling of fullness or satiation, which may limit the intake of carbohydrates. Carb loading requires consuming a higher proportion of carbohydrates in the diet to maximise glycogen stores, so it's important to choose foods that provide a good carbohydrate-to-fat ratio.

  5. Suboptimal Macronutrient Balance: Carbohydrates are the primary macronutrient for providing energy during endurance exercise. By prioritising carbohydrates and minimising fats during carb loading, you can optimise your macronutrient balance to support performance and glycogen replenishment.

However, it's worth noting that some healthy fats, such as those found in avocados, nuts, and seeds, can still be included in moderate amounts as part of a balanced diet during the carb-loading phase. These sources of healthy fats provide essential nutrients and can help promote overall health.


B) High Fibre Foods

  1. Digestive Distress: High-fibre foods, such as whole grains, bran, legumes, and certain fruits and vegetables, can cause gastrointestinal discomfort, including bloating, gas, and even diarrhoea, especially when consumed in large amounts. This can interfere with your comfort, nutrient absorption and performance during the race.

  2. Slower Digestion: Fibre adds bulk to your meals and slows down the digestion process. This can result in a feeling of fullness and delayed gastric emptying, potentially affecting the timely absorption and utilisation of carbohydrates. During carb loading, the goal is to efficiently replenish glycogen stores with carbohydrates, so focusing on easily digestible options is preferred.

  3. Reduced Carbohydrate Intake: High-fibre foods often contain a significant amount of carbohydrates, but the fibre content can lower the overall carbohydrate availability. When carb loading, it is crucial to prioritise the intake of easily digestible carbohydrates to maximise glycogen stores. Consuming excessive fibre can inadvertently decrease the net carbohydrate intake.

  4. Potential for Bloating and Discomfort: Fibre can draw water into the gastrointestinal tract, leading to increased stool bulk. This can contribute to feelings of bloating and discomfort, which can be particularly undesirable during a race.

In general avoiding (or at least limiting) fatty foods and high fibre options during carb loading is advised to help optimise carbohydrate absorption, maintain a favourable macronutrient balance, and support efficient energy delivery during endurance exercise.


Additional Considerations


Tapering Training: Reduce training volume (taper) during the carb-loading phase to allow your body to recover fully and optimise glycogen storage. Maintain light exercise to keep your muscles engaged.

Individual Variations: Each athlete is unique, and preferences can vary. Experiment during training to identify the carb-loading strategies that work best for you.

Practice During Training Runs: Experiment with different carbohydrate sources and meal timings prior to your long runs in training to understand what suits your body and helps maintain energy levels. If you plan to include gels during your run to top up glycogen levels I'd strongly recommend practising with the brand you plan to use on race day.


The night before: Most people will chow down a big bowl of pasta the night before, but this isn't an approach I'd advise. I'd prefer to have my last 'large' meal at lunch the day before race day and just consume a more 'regular' sized meal at dinner (still higher carb), but I think a heavy meal too close to bed is only going to negatively impact sleep, which we could really do with making the most of the night before a race/event.

Pre-Race Meal: Consume a carbohydrate-rich meal 2-3 hours before the race to top up glycogen stores. Choose easily digestible options like oatmeal and banana, or toast with jam. I wouldn't opt for anything too heavy on the morning of the race and stick to foods that you know your body copes well with.


Hydration: Hydration is a crucial aspect of any nutrition plan, including during a carb load. Here are some guidelines for proper hydration during a carb load:

  1. Drink water regularly: Throughout the carb load, make sure to drink water regularly to maintain proper hydration. Water is essential for overall bodily functions and supports the absorption and utilisation of carbohydrates.

  2. Monitor urine colour: A useful indicator of hydration status is the colour of your urine. Aim for a pale yellow colour, similar to the colour of straw. If your urine is darker, it may be a sign of dehydration, and you should increase your fluid intake.

  3. Consider electrolyte balance: During a carb load, it's important to maintain a proper electrolyte balance. Electrolytes, such as sodium, potassium, and magnesium, play a vital role in fluid balance and muscle function. Including electrolyte-rich foods and beverages can help maintain proper hydration. Examples include sports drinks, coconut water, and electrolyte supplements.

  4. Pre- and post-workout hydration: If you have training sessions during your carb load, pay special attention to hydration before and after your workouts. Start your workouts well-hydrated and replenish fluids afterward to support recovery.

  5. Include hydrating foods: In addition to water and electrolyte-rich beverages, include hydrating foods in your carb load. Fruits and vegetables with high water content, such as watermelon, cucumber, oranges, and berries, can contribute to your overall hydration.

  6. Individualise fluid needs: Fluid needs vary depending on factors such as body size, sweat rate, climate, and activity level. While general recommendations suggest consuming 2-3 liters (8-12 cups) of fluids per day, individual variations may require adjustments. Monitor your body's response to fluid intake and adjust accordingly.

  7. Be mindful of excessive fluid intake: While hydration is crucial, excessive fluid intake can lead to hyponatremia, a condition characterised by low sodium levels in the blood. Avoid excessive water intake without balancing it with electrolytes, as it can dilute sodium levels. Listen to your body's thirst cues and balance fluid intake appropriately.

It's important to note that the specific hydration needs during a carb load can vary among individuals. Factors such as climate, sweat rate, and training volume should be taken into account. Consulting with a sports nutritionist or registered dietitian can provide personalised guidance and help tailor hydration strategies to your specific needs and goals.


Remember, proper hydration is essential for optimal performance and overall well-being. By staying adequately hydrated during a carb load, you can support your body's processes and ensure the effectiveness of the carb loading strategy.


Conclusion Carb loading is a powerful strategy that can significantly impact your performance. By implementing the dos and avoiding the don'ts, you can optimise your carbohydrate intake, enhance glycogen stores, and push your endurance to new heights.


Remember to experiment during training to find the best approach for your body. With effective carb loading, you'll be better prepared to achieve your race-day goals.

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