Carb Loading: What Is It And How Can It Help With Performance?


What is it?

Carbohydrate loading, or ‘carb loading’, is a method widely used to increase energy available for endurance events. During exercise, our muscles use glycogen, or stored glucose, for energy. Carbohydrates is the easiest food group for our body to convert to glucose. After about 90 minutes of exercise, carbohydrate levels are usually depleted and the body starts to run low on glycogen. Therefore, it has to revert to fats and protein, which are much more inefficiently converted, and so athletes often hit ‘the wall’, as their bodies are forced to work harder to produce readily available glucose.

The basis of carb loading, is to fill your muscles to the brim with glycogen; it won’t make you faster on race day, but it will hopefully allow you to perform your best for longer, and prolong hitting the dreaded ‘wall’. Carb loading is only really advised for events longer than 90 minutes (so typically marathons or longer-distance triathlons), as there is no benefit of having higher levels of carbohydrate stored if you’re activity does not demand it.


When to do it?

It’s not a good idea to try carb loading for the first time ever during the week of an event, so practise your carb loading during your training regimes before-hand, perhaps for those particularly long run or bike sessions.

You can’t completely fill your muscles with glycogen from just one meal, so the process of carb-loading takes perhaps 4-5 days. 4 or 5 days out, begin depleting glycogen stores by adapting a low-carb diet, along with some intense exercise to wipe out the glycogen that’s already in the tanks. The reason for this is that within 24 hours of the depletion of glycogen reserves, the body rebuilds the reserves and over the following few days, can actually store an above-average capacity of glycogen!

Then, for the final 2-3 days leading up to the event, begin a loading period; carbs should make up around 80% of your diet. The target is approximately 10g of carbohydrate per kilogram of bodyweight, so for example a person weight 70kg would aim to consume 700g of carbohydrate each day.


What to eat?

Some people equate carb-loading with overeating, particularly with favourite foods such as chocolates, cakes, desserts and pastries. This is not the case unfortunately! You should try and stay clear of high sugar and high fat foods. Sugary carbs (such as white potatoes, white bread, and chocolate etc) can spike blood sugar and then lead to a crash. So, take on carbs that provide slow-release energy such as sweet potatoes or wheat toast.

You also need to be wary of fibre intake in the days leading up to the race. Some high-carb foods get their carbohydrates from fibre (such as cereal and fruits). Taking in too much fibre can lead to bathroom issues, and the miles will only seem to go by slower if you’re desperately on the lookout for a lovely porta-loo! Therefore, try to keep your fibre levels consistent with what you’ve eaten during training to elude any toilet-related incidents during the race, and also to avoid bloating and tummy aches.

It’s important keep total caloric intake relatively similar to normal, but to increase the ratio of carbs to proteins and fats. Increasing body weight significantly can actually hinder performance on the day even more than skimping on carbs! However, do be prepared to see a slight rise in weight gain due to the high levels of water in carb-rich foods.