Carb Loading
You’ve heard of ‘carb loading’, but do you know how to do it effectively? Take our refresher course to fuel your next endurance outing in the best way possible
Everything you need to know
Carb loading is a term that transcends its target audience. Even those with no interest in endurance sport will tell you that eating a big bowl of pasta the night before a big run or ride is probably a good idea, while more seasoned distance dons often look forward to nothing more than the pre-event excuse to eat a mountain of beige food like it’s their last chance to do so. Within reason, such an approach makes sense. e question is, why?
“Carb loading is the practice of maximising glycogen stores (the glucose that fuels the muscles) before endurance exercise,” explains Aisling Pigott, registered dietitian and endurance runner.
“e longer you exercise for, the more glucose you use. And while you may take on carbs during the activity, it’s hard to make up for the energy being burned. When you have depleted carbohydrate stores, your body switches to rely on fat breakdown, which is slower and less e cient (for most untrained athletes), which can lead to hitting the ‘wall’. at is what you’re trying to avoid.” Adam Sutton, who is currently completing a Masters in Sport and Exercise Nutrition, and whose dissertation explored carbohydrate malabsorption during exercise, agrees: “By increasing carb intake while reducing exercise volume in the lead up to an event, the glycogen content of your muscles increases. at can improve performance during events lasting 90-plus minutes.”
DON’T GO CARB CRAZY
It’s got decades of good research behind it, and experts are in agreement that when exercising, particularly for more than that 90-minute mark, carbohydrates become our main fuel source. It follows, then, that when they’re depleted, performance is negatively impacted. However, not all carbs are created equal – despite what social media would have you believe.
Search #carbloading on Instagram and you’ll be met with photos of massive pizzas, giant bowls of zzy sweets and monster burgers, but stu ng your face isn’t quite what 50 years of research is recommending. “I can understand the tongue-in-cheek description,” says Pigott, “but it sends the message that we need to eat high-fat, sugary and salty food during periods of carb loading, when in truth healthy, balanced meals are appropriate.”
Both our experts agree, the recent demonisation of carbs plays into this social media mine eld: “It adds to the growing perception that carbohydrates are only contained within ‘unhealthy’ foods,” says Sutton. “Whereas if they are included as part of a healthy and balanced diet, and scaled correctly to the demand of someone’s training, they can help support performance, adaptation to training and general health.”
TAILOR YOUR APPROACH
When it comes to fuelling, approaches are as varied and as personal as our unique bodies, appetites and training regimes. “It’s about making sure the general diet contains su cient carbs to meet energy needs, then making small adjustments to diet and
dropping training in the lead up to an event,” explains Pigott. “Every sport, distance and length of activity needs to be considered. Some sports also facilitate eating during an event to keep muscles fuelled, but others make it impossible.” Sat up on a bike, cyclists are able to eat rice cakes, dense energy bars and cake, for example, but a marathon runner could never do that.
Research proves that changes in intensity, duration, terrain, experience of the athlete and altitude all impact carbohydrate needs, so where to begin?
“ere can be di erent time scales,” says Sutton. “In the days and three to four hours leading into the event, the athlete would look to increase daily carbohydrate intake, with the majority of carbs being low glycemic (low GI) – such as brown rice and wholewheat pasta – to increase the muscle and liver glycogen stores. en in the 30-60 minutes before the event, carbohydrates should be higher GI (simple sugars that are absorbed and accessed immediately, such as sports drinks, gels and sweets) and lower bre to o er an alternate carbohydrate source to the working muscle.”
You need to be careful, though, and employ a bit of trial and error before competing, because according to Sutton, “the increase in insulin, combined with the increased blood glucose uptake from exercising could result in rebound hypoglycaemia, so dizziness and fatigue.” Basically, don’t do all your training on orange squash and bananas, then take a bag full of gels to the event. Practice makes perfect.
“Compared to runners, cyclists are generally able to stomach larger volumes of food before an event”
Also, consider the type of exercise you’re doing. “Compared to runners,” says Sutton, “cyclists are generally able to stomach larger volumes of food before an event, simply due to the mechanical motion of the stomach contents during the activity. Runners are likely to want to leave a longer period of time between the last feed and the beginning of exercise.”
If you want to avoid gastrointestinal discomfort, go for carbs with a lower bre content as you get closer to the starter gun being red, and limit fat and protein intake from four hours before you stand on the start line, as they take longer to digest.
ASSESS YOUR NEEDS
As a rough guide in the run-up, sports nutrition guidelines suggest up to 10g carbs per kg bodyweight per day. “at sounds like a lot,” says Pigott, “but for many athletes it’s bene cial.” To put it into context, a 76kg man would need to put away 760g of carbs daily in the two to four days leading up to the event, then on the nal day have a little less to avoid discomfort – and opt for lower bre foods.
at’s for the long and slow stu , but when the intensity increases and duration drops, carbohydrate intake needs to be adjusted accordingly. “Refuelling and having rested muscles with enough energy is important,” says Pigott, “but over-egging it and having high-calorie meals before a short burst of activity will just make you slower and more sluggish.”
A 20-minute HIIT session doesn’t need a particularly focused approach to carbs, just a generally healthy diet.
“e body naturally stores enough glycogen to support roughly 90 minutes of exercise,” says Sutton. He points to a study among cyclists, who raced to exhaustion at maximum intensity. Consuming a low-carb diet for three to four days prior impaired the cyclists’ times, compared to a group who had consumed a high-carb diet. However, when the scientists compared the high-carb group to cyclists who ate a moderate carbohydrate diet all the time, the di erence disappeared.
Carb loading can make a big di erence to performance. By making a habit of upping your intake of healthy, wholegrain, slow-release carbs in the days leading up to an event, then tapering o and relying on higher-GI, easily digestible options, you can boost your chances of success. According to research conducted by the Sports Science Institute of South Africa, a smart approach to pre-race carbs can improve endurance performance by as much as three per cent – that’s seven minutes o a four-hour marathon time. In other words, it’s worth getting right.