What Is Carbohydrate Loading?
Article by Dylan Bowe
Carbohydrates are one of the three main macronutrients in the diet, alongside protein and fat. All of these nutrients are important for health, wellbeing and sports performance. Carbohydrates are the main energy source in the body, organs need glucose (which is what carbohydrates in the diet break down to once ingested) such as the brain, and muscle requires glucose to perform. Therefore, eating sufficient carbohydrates is vital both for general wellbeing and also optimising athletic performance. The body can make glucose from other nutrients such as protein, through a process called gluconeogenesis, however this is not as optimal to fuel performance.
As well as carbohydrates, we have protein and fat too. Proteins are the building blocks of life, with every cell in the body containing protein. They are needed for growth, repair and maintenance in the body. Protein has a variety of essential functions, including: acting as a transport carrier in the blood, enzymes, antibodies, hormones and peptides.
Fats allow the body to store energy, cushion organs, help make hormones, absorb fat soluble vitamins (vitamin A, D, E, K) and help with the integrity (quality) of cell membranes.
Simple vs complex carbohydrates
Simple carbohydrates are easy for the body to break down into glucose, as they have 1-2 strands of sugar molecules, and these are found in foods such as honey, fruit, table sugar and milk. It’s suggested simple carbohydrates should be consumed around exercise, as they are broken down much faster and help with fuel performance prior to exercise, or replenish muscle glycogen after exercise.
Complex carbohydrates are often the main source of carbs in the diet. They are slower release and usually contain fibre and a variety of micronutrients (such as beans or lentils), and also they satisfy hunger for longer due to the complex nature and also because of the higher fibre content. Complex carbohydrates take longer to break down as they are comprised of longer strands of sugar molecules, and are found in foods such as rice, pasta, potatoes and bread. The more a person exercises, the higher their carbohydrate demands. Intakes can range from 3-7+g/kg/day, so a 70kg individual may need to consume anywhere from 210-500+g carbohydrates per day, depending on the intensity and volume of their training, and their physical activity levels.
What actually is carb-loading and is necessary?
Now that we understand how important consistent carbohydrate consumption is for performance, we can look at carbohydrate loading and its benefits.
Carbohydrate loading can be defined as a strategy in which athletes increase their carbohydrate intake in the days leading to a competition in order to increase muscle glycogen stores. This in turn can have a positive effect on performance by delaying the onset of fatigue in endurance sport (Sedlock, 2008). Little research has been done on carbohydrate loading in anaerobic, short burst, high intensity sports, however, according to Johnson (2022) it is not necessary for short duration exercise but an adequate amount of muscle glycogen is a more important factor for performance. Endurance exercise that is more than 90 minutes supports the practice of carbohydrate loading as a strategy to enhance exercise capacity and performance (Johnson, 2022). Previous research showed that muscle glycogen stores should be depleted for three days then consumption of carbohydrates for three days prior to competition could stimulate muscle glycogen replenishment (Bergström et al., 1967). However, it has now been shown that depletion does not need to occur, especially in trained athletes, and the most important thing is a high consumption of carbohydrates 24-48 hours prior to the event, especially if glycogen stores are not in a depleted state.
There are a variety of recommendations and strategies when it comes to loading on carbohydrates prior to competition, with World Athletics recommending elite runners 10-12g/kg bodyweight in the 36-48 hours pre-race, meaning a 65kg individual would consume 650-780g carbohydrates (Burke et al., 2019). Other strategies may include only slightly increasing carbohydrate intake for 5-7 days prior to competition, in combination with tapering and lowering training volume. It may be wise to choose a strategy in between these mentioned, such as carbohydrate loading for two days prior, or possibly even three if individuals find it difficult to consume the large amount of carbohydrates required. A 24-48 hour loading strategy is a solid recommendation for trained athletes (Bussau et al., 2002), and a good starting point before individuals tweak the strategies to what works best for them. Johnson (2022) recommends an intake of 8-10g/kg for at least this 24-48 hour period before competition, to maximise glycogen stores, which for a 65kg athlete would be 520-650g carbohydrates.
How can we incorporate carb loading into our routine?
It is important to follow a few simple steps to make the loading strategy more manageable.
Firstly, adding larger portions of carbohydrates to each meal from sources such as pasta, potatoes and rice will help, along with consuming easily digestible, low fibre sources such as fruit juices. However, as fruit juices contribute to our daily sugar intake, it’s recommended that we consume no more than 150ml per day.
Along with this, snacking 2-3 times per day can help increase carb intake, and also low residue/low fibre foods, as these will decrease the stress on the gastrointestinal tract and hopefully prevent any gut issues that can occur with sharply increasing food intake. This means possibly eating less fibrous vegetables in the days prior to your competition, and sticking to ‘white’ versions of grains such as bread and pasta, and drinking simple carbohydrates from sports drinks such as maltodextrin or fruit juices. One large potato weighing roughly 300g contains around 60g of carbohydrates (check out the chart below to see 60g carbohydrate portions), so you would have to consume 10 of these to hit a target of 600g carbohydrates! Aiming for anywhere from 100-150g carbohydrates per meal can create a better structure, and this would look like 2 large baked potatoes, 150g low fibre cereal (such as Coco Pops) along with milk, or 2 cups of cooked white rice along with a 300ml glass of orange juice. Once you break it down this way, it is much more manageable to consume this intake prior to an event.
Lastly, an important consideration is that there may be gender differences in glycogen storage, as some research has shown less performance increases in females compared to males when they are both prescribed a high carbohydrate diet (Tarnopolsky et al., 1995), this may be due to women having lower resting muscle glycogen stores to begin with. Because of this, it is recommended that women increase both total calorie and carbohydrate intake during the loading phase, in order to maximise glycogen increases.
Summary
Carbohydrate loading is just one tool from the tool box for athletes to improve their performance. Consistently high carbohydrate intake throughout peak and off seasons is critical for athletes to fuel training sessions, and also optimise recovery, as adequate glycogen availability can improve muscle repair (Knuinam, Hopman and Mensink, 2015). Using a loading strategy such as the one outlined above, can aid in maximising the fuel your muscles use for sports performance, when combined with a proper training plan and diet.
This blog was written by Dylan Bowe, who is from Donegal, Ireland and has a First Class Honours BSc in Sport Science from Athlone Institute of Technology. He is now currently studying for an MSc in Clinical Nutrition from University of Aberdeen. His interest for nutrition started many years ago, when he had a poor relationship with food and was overweight. With time, and lots of trial and error, he managed to overcome these issues and now wants to empower people to feel comfortable in their own skin and have a positive relationship with food. Dylan also trains in Brazilian Jiu Jitsu and has a keen interest in other combat sports, and this in combination with his studies, gives him a strong insight into how to help any high level athlete perform at their best. You can also follow him on Instagram: @dbowe_nutrition.
References:
(1) Bergström, J., Hermansen, L., Hultman, E. and Saltin, B. (1967) Diet, muscle glycogen and physical performance. Acta physiologica scandinavica, 71(2‐3), pp.140-150.
(2) Burke, L.M., Jeukendrup, A.E., Jones, A.M. and Mooses, M. (2019) Contemporary nutrition strategies to optimize performance in distance runners and race walkers. International journal of sport nutrition and exercise metabolism, 29(2), pp.117-129.
(3) Bussau, V.A., Fairchild, T.J., Rao, A., Steele, P. and Fournier, P.A. (2002) Carbohydrate loading in human muscle: an improved 1 day protocol. European journal of applied physiology, 87(3), pp.290-295.
(4) Johnson, B. (2022) Carbohydrate loading for endurance - still a good practice?, Science for Sport. Available at: https://www.scienceforsport.com/carbohydrate-loading-for-endurance-still-a-good-practice/ (Accessed: January 15, 2023).
(5) Knuiman, P., Hopman, M.T. and Mensink, M. (2015) Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise. Nutrition & metabolism, 12(1), pp.1-11.
(6) Sedlock, D.A. (2008) The latest on carbohydrate loading: a practical approach. Current sports medicine reports, 7(4), pp.209-213.
(7) Tarnopolsky, M.A., Atkinson, S.A., Phillips, S.M. and MacDougall, J.D. (1995) Carbohydrate loading and metabolism during exercise in men and women. Journal of applied Physiology, 78(4), pp.1360-1368.