Is your idea of a carbohydrate load a big bowl of pasta the night before your marathon? If so, it's time to re-think your pre-race strategy. In this short blog I will explain the what, the why, the how and the when for carbohydrate loading.

Why carbohydrate load before a race?

A carbohydrate load well executed is one that has you ready at the start line with maximal glycogen stores (aka your stored carbohydrate). Depletion of glycogen is a major cause of fatigue during exercise. By optimising your carbohydrate status within the muscle and liver (where glycogen is stored) you get performance benefits. Filled glycogen stores will allow you to run for longer and harder before running out. It's well documented that runners who start a race well fuelled are more likely to finish the race stronger and faster than those who just rely on willpower alone.

When should I do it?

It is recommended for events lasting more than 90 minutes. The carbohydrate loading phase occurs at least 24 hours before, ideally up to 72 hours before the event. Some people prefer to scale back a little the day before an event but push their intake the 2 days prior – this can help with feeling less bloated.

What should I do?

72–48 hours before an endurance event – You want to ensure your diet is rich in carbohydrates. Guidelines suggest up to 10–12g/kg body weight of carbohydrate per day (for a 60kg athlete this is around 600–720g of carbs, the equivalent to 30–36 slices of bread!). However, this can be quite difficult to achieve due to volume of food required, even in trained elite athletes. Intakes of around 8g/kg body weight may be more realistic (for a 60kg athlete around 480g of carbs, which is around 2000 calories from carbs). To keep things simple, I would suggest runners aim to increase overall carbohydrate intake in the 2–3 days leading up to their event: increase portions of carbohydrates at each meal, choose carbohydrate-rich snacks throughout the day, and use carbohydrate-rich fluids to help maximise intake without causing unnecessary gastrointestinal upset.

Choose high-carbohydrate meals, particularly from low-fibre options such as white breads and pasta. Aim for most of the meal to be carbohydrate with a small contribution from proteins, fats and fibre. This will look different to what is considered a more everyday healthy balanced diet – remember this is only a short-term change to help maximise stored energy ready for race day.

What about race day?

1–4 hours before an endurance event – Consider this the fine-tuning part of preparations. Some of the glycogen will have been used overnight during sleep. Therefore a carbohydrate-rich breakfast will help restore glycogen. On race day it is recommended an intake of 1–4g per kg body weight, 1–4 hours prior to the event, to top up glycogen stores following the overnight fast. Allowing sufficient time to eat and digest a meal is also important – this may mean getting up earlier to do so.

Why have I gained weight?

It is perfectly normal to see a rise in scale weight during the carbohydrate loading phase. This is a temporary shift in weight due to water retention. For every 1g of glycogen the body stores around 3g of water with it. As you use up the glycogen, the water weight is lost.

Examples of carbohydrate-rich foods

  • Breakfast: White bagel toasted with butter and jam, banana and small glass of OJ
  • Lunch: Bowl of white pasta with tomato sauce and sprinkle of cheese, or small portion of chicken and pot of full-sugar jelly
  • Dinner: Savoury rice dish, bread roll and pudding (e.g. sponge cake and custard)
  • Snacks: Low-fibre cereal and milk, crackers, biscuits, scone, toast, fruit bread, jelly, fruit yoghurt, banana, glass of milk (or flavoured), sports drinks, salted pretzels, rice cakes, custard, rice pudding

Final word

Think of the carbohydrate load as the final part of your race prep – imagine it's like going on a long car journey: you're going to want to fill the tank before you set off!