What is carb loading?

Felicity Mann

02 August 2017

Why should you carb load?

You may have heard of high profile endurance athletes’ carb loading before a marathon or match, but what exactly does it entail?

Essentially, carb loading is all about trying to supply your muscles with as much glycogen as possible.

When your body is digesting carbs, it breaks them down into sugar, or glucose, which is then stored in your muscles and liver as glycogen. Glycogen can then act as your body’s main fuel source, sustaining you through bouts of rigorous exercise and increasing your capacity for endurance.

The longer you exert your body, the more likely it is that you will eventually deplete your glycogen stores and ‘hit the wall.’ Once you have hit the wall and depleted your stores of glycogen, it may become difficult for you to continue with your activity as you may be overcome by exhaustion and fatigue.

Fat vs. Carbs

While most athletes do subscribe to carb loading, there are those that have concerns about the practice and insist that fat should be used as the body’s primary fuel source instead of carbohydrates.

This line of thinking does have some merit. Our bodies were originally adapted to use fat as its primary fuel source and it’s only very recently that our bodies have started to evolve to use glucose instead. This is why some sport stars prefer to switch to a high fat, low carb diet in order to adapt their body’s back to fat.

Adapting your body for using fat as its fuel instead of glucose can be difficult though. Your body can only adapt if your glycogen stores are depleted, meaning that some have to adjust to a Ketogenic diet in between bouts of fasting. 

Nevertheless, fat adaptation does hold some serious benefits, allowing you to burn fat more efficiently and increasing your anaerobic threshold. One study revealed that endurance athletes, who had stuck to a ketogenic diet, were capable of burning 59% more fat than endurance athletes on normal diets, as well as having a higher anaerobic threshold.1


The side-effects of carb loading

Carb loading can be beneficial for athletes but, if done incorrectly, it can also lead to a number of unwanted and uncomfortable side effects. Carb loading isn’t an excuse to binge on burgers and essentially eat whatever you want. Those that do try to accumulate glycogen quickly learn that the hard way.

  • 1 – Poor digestion: If you do decide to eat nothing but simple carbohydrates, you will experience some digestive side-effects. A lot of carbohydrates are chockfull of fibre, which is normally a good thing. However, if you absorb too much fibre from your diet, your digestive system will struggle to break it down properly, leading to bloating and constipation – not so good if you have to run a 20K marathon the next day!
  • 2 – Raised blood sugar levels: Consuming carbohydrates will naturally raise your blood sugar levels. If your blood glucose levels become elevated, it can cause you to experience headaches, blurred vision and fatigue, which is why you have to source low GI forms of carbohydrates that won’t have the same impact on your blood glucose.
  • 3 - Increase in weight: Finally, you have to consider your weight. As I shall go on to discuss, many athletes are encouraged to rest in the days before an event. This respite, in combination with a high carb diet, can lead to weight-gain as your body will start to store excess water and calories, increasing your body fat.

When should I carb load?

Carb loading has to be done responsibly; otherwise you may risk doing more harm than good, especially if you start loading up on carbs unnecessarily.

Consider the activity you are going to be engaging in – are you going to be active for over 90 minutes? If not, I wouldn’t bother trying to carb load as your body should still have plenty of glycogen to fuel your muscles.

If you are going to be participating in an endurance sport such as running, cycling or playing tennis, and you’re confident you will be vigorously active for over 90 minutes, I would start to prepare your body first before focusing on carb loading.

One popular method of preparing for an endurance sport is known as ‘tapering.’ Tapering refers to the idea of focusing on your recovery as well as your fitness. Starting about a couple of weeks before your race or marathon, gradually reduce your mileage and the intensity of your workouts.

Once you have established your tapering routine, then you can start to think about carb loading.

What should I eat to carb load?

Everyone has different ideas about how to carb load successfully, but I personally subscribe to the idea that you should start carb loading two or three days before your event. Carbohydrates usually form about 60% of your daily calorie intake but when loading, you should try and increase this to around 70-80%, or 8-10g per kilogram of weight.2

It might be tempting to immediately binge on simple carbs and supersize your meal portions, but this  way of thinking is irresponsible and will lead to the aforementioned side-effects I discussed earlier. Instead, rather than increasing your portion size, simply eat smaller meals more regularly throughout the day.

Try to find forms of carbohydrates that are easy to digest. Loading up on burgers, pizza and white pasta will definitely cause some digestive problems for you further down the line, so instead focus on complex forms such as wholemeal bread, oatmeal, potatoes and brown rice.

Don’t be afraid to include some fruit and veg in there either. Bananas are definitely your carb-loading friend as they contain moderate amounts of dietary fibre and are easy to digest. I would also suggest investing in some nut-butters – a brown bagel topped with almond butter and slices of banana makes for the perfect carb loading snack!

As I mentioned earlier, loading up on carbs can increase your blood sugar levels so try to focus on low GI forms of carbs too. These can include nuts, pulses, bran flakes and leafy green vegetables. Avoid cakes, packaged cereals and white bread – these are highly processed and may cause your blood sugar levels to spike!

Finally, make sure you are drinking plenty of fluids. Drinking a glass of fruit juice will help to increase your carb intake but I’m talking about good old-fashioned plain water. Water will help to keep your digestive system in check and prevent you from experiencing the symptoms of dehydration. Forget about fizzy, caffeinated drinks and focus instead on healthier alternatives.

I would recommend including Biotta’s Beetroot Juice in your routine. Research has concluded that drinking just 70ml of beetroot juice before a workout can improve your oxygen utilisation and performance. This is because beetroot juice is able to dilate your blood vessels and increase your oxygen availability, enhancing your endurance! Not to mention, Biotta’s Beetroot Juice is packed full of iron, potassium and nitrates which can help to regulate your blood pressure and support your red blood cell production. Not bad!

What about during the event?

Whether you’re running or cycling, I think it’s still important you take a healthy snack with you. Not only will this top up your carb intake on-the-go, it can also ensure that you’re getting the nutrients you need to power through. For more ideas about healthy snacks for running and cycling, please check out our blogs, how to boost your energy during a run, or 7 great snacks for cycling!

Again though, drinking water should play an important role for all the reasons that I spoke about earlier. If you are sweating, not only will you be losing fluids though, you will also be losing important electrolytes and trace minerals.

It might be worthwhile taking a sachet of our Balance Mineral Drink with you. Simply mix the sachet into your water bottle and voila! You should have a delicious, strawberry-flavour drink that’s chockfull of electrolytes and trace minerals to help keep you hydrated and to fight off the symptoms of fatigue!

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