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Carb loading is a dietary approach used by athletes that involves consuming a high-carbohydrate diet, usually 1 – 3 days prior to a long-duration endurance event to increase glycogen stores in their muscles as part of the preparation process.
Such events include marathons, long-distance road cycling, long-distance swimming, or if athletes are playing a tournament with back-to-back games, such as during basketball championships or soccer tournaments.
Modifying diet and exercise routines aims to create a larger "fuel tank" of stored muscle glycogen, our body's preferred energy source during prolonged, high-intensity activity. Before we dive more into this practice, let’s first zero in on what carbohydrates are.
Carbohydrates, often referred to as carbs, are one of the primary macronutrients, alongside proteins and fats, vital to our bodily functions. They are the body's main energy source, supplying the energy that our cells require to carry out their daily functions.
Carbohydrates are made up of small molecules of sugars, or saccharides, that when combined in various ways form different types of carbohydrates. Based on their structure and complexity, carbohydrates can be divided into 3 main types.
Simple carbohydrates (sugars). Simple carbohydrates, also known as sugars, consist of one or 2 saccharides – monosaccharides or disaccharides. Examples of sugars include glucose, sucrose, and fructose. They are quickly absorbed and provide a rapid source of energy. Sugars are found naturally in fruits, milk and milk products, and simple sugars are also added to a variety of processed foods and drinks like sweets and soft drinks.
Complex carbohydrates (starches). Complex carbohydrates, or starches, consist of many saccharide units linked together and are found in foods such as potatoes, bread, rice, and pasta. These carbohydrates are digested more slowly than simple sugars, providing a more sustained energy release due to their lower glycaemic index. This is particularly true of starches that contain fibre (e.g. wholemeal bread, potatoes with skin, and brown rice).
Dietary fibre. Dietary fibre is a type of carbohydrate that our bodies cannot digest. There are 2 types of fibre: soluble, which dissolves in water and can help lower blood glucose and cholesterol levels, and insoluble, which can help food move through your digestive system, promoting regularity and helping prevent constipation.
It is important to understand the different types of carbohydrates and their roles to better optimise dietary strategies such as carb loading, to improve athletic performance.
Carb loading is primarily intended for endurance athletes preparing for prolonged, intensive events, typically those lasting 90 minutes or longer. This is because such strenuous activities deplete glycogen stores in muscles, which could result in fatigue and reduced performance. By carb loading, athletes aim to maximise their glycogen storage, which can enhance their endurance and delay the onset of fatigue.
Examples of activities where carb loading may be beneficial include marathon running, long-distance cycling, triathlon events, and long-distance swimming. However, it's less relevant for sports involving short bursts of activity, such as sprinting or weightlifting, and for activities of a lower intensity or shorter duration.
While carb loading can be beneficial for endurance athletes, it's important to note that it should be approached with care. Not every endurance athlete will respond to carb loading in the same way, and individual dietary needs can vary widely. It's recommended to work with a sports dietitian to develop a personalised nutrition strategy; they’ll be able to advise on the exact amount of carbohydrates an athlete should consume, and the duration of this diet prior to competition, to avoid under or over consumption of carbohydrates.
Carb loading primarily benefits athletes by enhancing their endurance. By maximising muscle glycogen, the body's preferred form of carbohydrate during exercise, athletes can maintain a high level of exertion for longer periods during endurance events, thus delaying the onset of fatigue.
Consuming glycogen after exercise helps replace muscle glycogen depleted during exercise, and aids in storing more glycogen as an adaptation to training. This is especially beneficial when events are spaced closely together – generally, if events are less than 8 hours apart.
The importance of carbohydrates extends beyond physical performance to mental acuity as well. Sufficient carbohydrate intake fuels the brain, aiding in maintaining focus and decision-making during endurance events. Research suggests that consuming a high carbohydrate intake prior to a long-duration endurance event may delay the onset of fatigue and reduce risk of injury, further boosting the athlete's capacity for sustained performance. However, carb loading strategies should be personalised, as individual needs and responses can vary greatly.
Timing is crucial when it comes to carb loading. Begin the process approximately 36 – 48 hours prior to your event. This timeframe allows your body to store glycogen, the primary fuel source during prolonged exercise.
To determine the right amount of carbohydrates to consume, it's advisable to consult with a sports dietitian. They can assess your individual needs and recommend a specific daily intake. Generally, athletes are advised to consume around 8 – 12 grams of carbohydrates per kilogram of body weight per day during the carb loading phase.
In conjunction with increased carbohydrate consumption, it's important to implement an exercise taper during this period. Reducing the intensity and volume of your workouts allows your muscles to recover and glycogen stores to be maximised.
A useful tip would be to practise carb loading as part of training prior to the actual competition or event. This will allow you to experiment with different strategies, gauge their effectiveness, and make any necessary adjustments. By doing so, you can optimise your performance and fuel your body effectively for the endurance challenge ahead.
It's important to note that carb loading protocols may vary among athletes. To develop a personalised plan, it is recommended to discuss your specific needs with both a sports dietitian and physical trainer. They can guide you through the process, fine-tuning the dietary and training aspects to suit your individual requirements.
Carb loading can come with several pitfalls that can interfere with its success. These include:
Carb loading doesn't mean you should increase your total daily calories. Rather, it involves adjusting the proportion of your calorie intake that comes from carbohydrates. Overeating can lead to weight gain and feelings of heaviness or discomfort, which are not conducive to optimal performance.
Do not neglect to consume sufficient fluids prior to an endurance event to ensure that you are adequately hydrated. Failing to properly hydrate can lead to dehydration and negatively impact your performance and recovery.
Another common mistake is not consuming enough carbohydrates to maximise glycogen stores. For effective carb loading, aim for 8 – 12 grams of carbs per kilogram of body weight each day. The exact amount of carbohydrates required prior to an event should be discussed with a sports dietitian, as this will vary across different individuals and different types of sport.
This can come in the form of refined carbohydrates like bread, rice, and noodles. Although foods and drinks high in refined sugars, such as smoothies, cereal bars, and flavoured milks are generally not recommended on a regular basis, it is acceptable to use these foods and drinks to meet the higher-carbohydrate demands of carb-loading prior to endurance events.
Some athletes consume too much fibre while carb loading, leading to gastrointestinal discomfort. In the final days leading up to the event, switching to low-fibre carbohydrate sources such as white bread instead of wholemeal bread, or regular pasta rather than wholegrain pasta can help alleviate potential digestive issues.
Some people make the mistake of consuming high-fibre or fatty foods during their carb loading phase. Fatty foods can displace the carbs needed to fill glycogen stores, and while high -fibre foods like vegetables, whole grains and fruit are healthy and recommended on a regular basis, these should not be overconsumed during the carb loading phase because they can cause digestive discomfort especially if consumed in large amounts.
While the focus of carb loading is on carbohydrates, protein should not be completely overlooked. Including a moderate amount of protein in your meals can aid in muscle repair and recovery. Speak to a sports dietitian to understand your individual protein needs and how adequate protein can be incorporated into a high-carbohydrate diet.
The days leading up to a race are not the time to try a new dietary strategy. Every athlete is unique, and you should use your periods of training to trial and fine-tune your carb loading plan.
When carb loading, you should avoid high-fat and high-fibre foods and alcohol. Instead, what you should go for are foods that are high in carbohydrates and low in fibre to maximise glycogen storage and minimise digestive discomfort. These include:
Refined grains. Choose white bread, white rice, or pasta. While whole grains are generally healthier, they're higher in fibre, which can lead to digestive discomfort when consumed in large quantities. Refined grains, on the other hand, are more easily digested, and are therefore more appropriate to meet the high carb needs during carb loading.
Starchy vegetables. Potatoes and sweet potatoes without skin, as well as taro are some good choices.
Fruit juices and canned fruits. These are high in simple sugars which are more carbohydrate-dense than fresh fruit. It is acceptable to include foods and drinks high in refined sugars, such as juices, flavoured milk, canned fruit, and smoothies as part of the diet to meet the high carb needs during the carb loading phase.
Low-fat dairy. Milk, yogurt, and low-fat cheeses provide carbohydrates along with some protein for muscle recovery. Flavoured low-fat milks and yoghurt are a good way to provide lots of carbohydrates in a small volume.
If you're interested in learning more about carb loading or are going to go on the diet for an upcoming event, our experienced dietitians can help. Visit our Nutrition & Dietetics page to learn more.