Carb loading is an effective strategy to improve performance in endurance events/races. Some people often think carb loading means eating larger portions or a large bowl of pasta the night before an event. Below we provide an overview of what carb loading is and top tips for reaching your targets.
What is carb loading?
Carbohydrates, or carbs, are the main source of energy for endurance exercise. Carbs are stored in our muscles in the form glycogen. Our muscles can store up to around 400g of carbohydrates, equivalent to 1600 calories. During exercise, these stores are used up and start to deplete after around 90 minutes. After this point, it becomes difficult to sustain performance as you run out of fuel and run the risk of "hitting the wall".
Carb loading is an effective method to increase and enhance your carb stores in preparation for an endurance event/race - essentially filling up your tank. It has been shown to improve performance by 2-3%. (1)
Carb loading involves increasing your carb intake from 3 days before the event, eating 8-12g of carbs per kg of your bodyweight (BW) per day, whilst also tapering your exercise to reduce the amount of carbs being used up. For example, for someone who weighs 60kg, this means 480-720g of carbs per day.
Your intake depends on the duration and intensity of the event/race, with the upper end ideal for competitive and ultra-endurance events, such as an Ironman. You can’t completely fill up your muscles and liver with glycogen with a single meal, which is why you should start carb loading 1-3 days before your event/race. As carbohydrate stores start to deplete after around 90 minutes, it is not necessary to carb load to events/exercise of shorter duration.
Top tips to reach carbohydrate targets
Avoid high fibre foods/carbs as these will fill you up (and potentially prevent reaching your intake goals). Stick to simple, refined carbs such as white bread, bagels, pasta, rice, rice pudding and sweets.
Reduce protein and fat intake to prioritise carb intake. Having high protein, high fat meals will make you feel full, increasing the risk of not eating enough carbs.
It's essential to keep hydrated and maintain electrolyte balance whilst carb loading. Sports drinks and gels which contain carbs and electrolytes can be helpful to obtain both at the same time.
Have fruit juices and smoothies to boost carb intake. These will also help with hydration.
The day before race/event day, front load your intake to have a larger proportion in the morning/afternoon. Don’t leave it all for the evening!
Carbs are stored with water in our muscles, therefore you will likely gain some weight (water weight) whilst carb loading. To prevent gaining body fat, it's important to stick within your daily calorie targets whilst carb loading, adjusting your macronutrient ratios so that carbs are more than protein and fat. It is best to plan your carb loading strategy in advance and avoid simply having larger portions of your regular meals. You should try out carb loading during training, for example before one of your long runs/rides/sessions, before implementing for race/event day.
References:
Hawley JA, Schabort EJ, Noakes TD, Dennis SC. Carbohydrate-loading and exercise performance. An update. Sports Med. 1997 Aug;24(2):73-81. doi: 10.2165/00007256-199724020-00001. PMID: 9291549.
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