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What Is Carbohydrate Loading?

Carbohydrates are the body’s main source of energy. ‘Pasta parties’ have become a common part of the lead up to long distance endurance events. However, should we be ‘carb loading’ or is it less beneficial than we might think ?

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September 7, 2021

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As an endurance athlete, you know that performance depends on both training and proper nutrition. One of the most important nutrition strategies for endurance sports is carb loading, which can boost glycogen stores and improve performance.

However, carb loading can be a tricky process that requires careful planning and execution. In this article, we’ll delve into the science behind carb loading, explore different techniques, and provide tips to avoid common mistakes. By the end of this article, you’ll be ready to incorporate carb loading into your training plan and achieve your best performance yet.


Carbohydrates are the body’s main source of energy. They are the most important fuel source for athletes as they provide the fuel to perform high intensity exercise. They are stored in the body as glycogen[1][2]. However, there is limited glycogen storage capacity within our bodies, so it’s important these stores are topped up with adequate carbohydrate before training and replenished after exercise. Your body can only store enough glycogen to sustain around 90 minutes of moderate intensity exercise. Performing high intensity exercise will utilise glycogen stores at an even quicker rate. Exercising beyond this, without sufficient fuel, energy levels drop and fatigue sets in. Therefore, if you are exercising for over an hour it is important to consume carbohydrate sources during exercise.


Carbohydrates are classified into two types: simple and complex. Simple carbohydrates are found in foods such as table sugar, honey, and fruit. They are quickly digested and provide a rapid source of energy. Complex carbohydrates, on the other hand, are found in foods such as whole grains, vegetables, and legumes. They take longer to digest and provide sustained energy. Complex carbohydrates are better for carb loading.


Carbohydrate loading, also known as glycogen loading or glycogen supercompensation, is a performance-enhancement strategy, most commonly used by endurance athletes before a competition or event[3]. Carbohydrate loading involves increasing carbohydrate intake around 1-4 days before an endurance event. Carbohydrate loading was first developed by Scandinavian researchers in the late 1960s and involved either a 3- or 6-day exercise and diet manipulation[1][2]. Increasing carbohydrate intake through dietary sources increases muscle glycogen stores and enhances performance by delaying the onset of fatigue[1][2][4][5]. It has been reported that performance benefits from carbohydrate loading are most likely to occur in events lasting longer than 90 minutes[6]. Therefore, endurance events such as marathon and ultra-running, long distance cycling and triathlon, are all events which would benefit from carbohydrate loading.


Carb loading can enhance endurance performance in several ways. Firstly, it increases the amount of glycogen stored in the muscles and liver, which can extend the duration of exercise before fatigue sets in. Secondly, carb loading can improve the body's ability to use fat as a fuel source, which can help prolong exercise further. Thirdly, carb loading can increase the body's tolerance to exercise-induced acidosis, which is essential for high-intensity events.

Carb loading is not necessary for all endurance events. It is typically only recommended for events that last longer than 90 minutes, such as marathons, triathlons, and long-distance cycling events.


There are lots of factors that can determine the effectiveness of carbohydrate loading. For example; type of carbohydrates ingested, timing of increased carbohydrate intake relative to the performance event, the type of performance event and gender[3]. Individual athletes have different levels of tolerability in relation to high carbohydrate intake. Side effects such as bloating and general gastrointestinal discomfort that often accompany high carbohydrate intake. The menstrual cycle phase may also determine the effectiveness of carbohydrate loading. For example, it has been shown that women have a greater capacity for storing glycogen during the luteal phase in comparison to the follicular phase[7][8][9]. However, due to the dominant hormones present during the luteal phase, women are not as efficient at utilising their glycogen stores. It is possible to eat too much carbohydrate, just as it is with any other food group. Therefore, it is important to keep following a balanced diet leading up to a long-distance event not focusing solely on carbohydrates. It also needs to be remembered the point of carbohydrate loading is maximise glycogen stores, and there is a limit to how much your body can actually store.


Carbohydrate loading is a popular technique used by athletes to increase their glycogen stores before a competition. This technique involves manipulating the amount of carbohydrates an athlete consumes in the days leading up to an event to maximise their energy levels and performance. There are many different carb loading techniques, but the three most common ones are the classic 6-day carb loading method, the modified 3-day carb loading method, and the 1-day carb loading method.


The classic 6-day carb loading method is the most well-known technique. This traditional method of carb loading involves a depletion phase, which may involve a reduced-carbohydrate diet and/or glycogen-depleting exercise. This depletion phase is followed by a high-carbohydrate diet for 3-4 days. During this time, athletes consume around 8-12g of carbohydrates per kilogram of bodyweight per day. This is followed by a reduction in training intensity or increased rest in the last 2-3 days leading up to the competition.

One downside to the classic 6-day carb loading method is that the depletion phase can leave athletes feeling fatigued and sluggish. This can negatively impact their training and performance. However, when done correctly, this method can significantly increase an athlete's glycogen stores, leading to improved endurance and performance.


The modified 3-day carb loading method is a variation of the classic 6-day carb loading method. This method involves a shortened depletion phase followed by a high-carbohydrate diet for 1-2 days. This method is useful for athletes who want an easy and quick carbohydrate boost for their competition without undergoing the long glycogen-depletion phase.

The modified 3-day carb loading method is less intense than the classic 6-day carb loading method, making it a popular choice for athletes who are new to carb loading. However, it may not be as effective at increasing glycogen stores as the classic method.


The 1-day carb loading method is a last-minute carb loading technique that can be used for athletes who cannot afford to undergo a longer period of preparation, such as during a multi-day event. This method involves consuming about 10-12g of carbohydrates per kilogram of bodyweight for one whole day prior to the competition.

The 1-day carb loading method is not as effective at increasing glycogen stores as the classic 6-day carb loading method. However, it can still provide a quick boost of energy for athletes who need it. It is important to note that this method should only be used as a last resort and should not be relied upon as the primary carb loading technique.

Each method has its own benefits and drawbacks, and you should choose the method that best suits your individual needs and goals.


There are some common mistakes that athletes make when carb loading, which can negatively impact their performance.


While carb loading can be beneficial for many athletes, it is important to understand when it might not be appropriate for your body and your sport. For example, some sports highly rely on strength and power, such as bodybuilding and sprinting. In such sports, the weight gain that comes with carb loading may be detrimental to performance.

It’s important to consult with a sports nutritionist or a healthcare professional to determine whether carb loading is appropriate for your body and your sport.


One of the biggest mistakes athletes make when carb loading is consuming too many or too little carbohydrates. Consuming too few carbohydrates during the loading phase may not give you the intended performance bump, while over-consuming carbs may lead to weight gain and sluggishness.

It is therefore important to find the right amount of carbohydrates for your body. This will depend on factors such as your body weight, the intensity of your exercise, and the duration of your event.

Find out how to calculate your carb intake further down this article.


The carb-loading phase is not the time to experiment with new foods or supplements that the body may not be used to. New foods can cause discomfort and may affect digestion, which can hinder performance.

Stick to familiar foods that you know your body can handle. This will help ensure that you are able to properly digest and absorb the carbohydrates, and that your body is able to use them efficiently during your event.


When carb loading, it is important to balance exercise and rest. The glycogen stores will be severely depleted if there is a lot of exercise undertaken during the preparation and loading period.. Ensure that you allow the muscles to rest and recover during the carb loading phase to allow them to store glycogen. This will help ensure that you have the energy you need to perform at your best during your event.



The amount of carbohydrates that an athlete should consume during carb loading varies with their body weight and the duration of their sports events. As a general rule of thumb, athletes could consume 7-12g of carbohydrates per kilogram of body weight, although this may need to be adjusted based on the individual’s physical ability or the expected duration of exercise.


Athletes should prioritise carbohydrates during the carb-loading phase, and be mindful of other macros in their diet. Eating a well-balanced meal with more carbohydrates and lower-fat macronutrients improves recovery time on subsequent training or events.

While increasing carbohydrate intake, athletes should not neglect their fat intake. Healthy fats, such as those found in nuts, seeds, and avocados, are essential for hormone production and overall health.

Renee McGregor recommends eating little and often not necessarily increasing volume or overall energy but changing the composition of the diet so it’s higher in carbohydrate. For example, swapping porridge and nuts to porridge with banana and honey or choosing to snack on malt loaf instead of yoghurt.

Overall, carb loading can be a useful tool for endurance athletes looking to improve their performance. By properly assessing their need for carb loading, calculating their carb intake, and balancing their macronutrients, athletes can optimise their performance during long-duration events.


‘Pasta parties’ have become a common part of carbohydrate loading in the lead up to long distance endurance events. However, there are numerous ways that you can meet your carbohydrate requirements beyond pasta. For example, bread, rice, noodles, potatoes, loaf cakes and bananas are just some of the options you could consider as part of your carbohydrate loading plan.

It’s also important to eat foods that can be better absorbed by the muscles and will not cause gastrointestinal discomfort. The glycaemic index (GI) determines the effect a certain food has on blood glucose with high-GI foods being broken down much quicker during digestion than low-GI foods and are absorbed by the muscles more effectively[10]. Foods with a high glycaemic load (GL) have a higher quantity of carbohydrates and together with high GI allow your muscles to efficiently obtain more carbohydrates.

A large consumption of high fibre (typically low-GI) foods can lead to gastrointestinal discomfort. Choosing foods lower in fibre will help to reduce the risk of developing gastrointestinal discomfort on race day. White potatoes are high-GI and GL and removing the skins reduces the fibre content. Therefore, mashed potatoes are an ideal choice when carbohydrate loading.
It is also normal to gain some weight over this period. For every gram of glycogen, your body stores around 2.6g of water too. This extra weight isn’t going to slow you down and it can be helpful in keeping you hydrated during the endurance event. Additionally, if you maintain adequate hydration then glycogen storage is more efficient.
It is important to understand that every individual athlete is unique. Therefore, carbohydrate loading can be an effective performance-enhancing strategy for some endurance athletes but perhaps not others.

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