Is a high-carb meal before an endurance event a good idea?
Eating a high-carb meal before an endurance event has been considered the norm for years. But is it the right thing to do, asks Rachel Jacqueline
If you're running a marathon, traditional wisdom suggests you should eat a bowl of pasta the night before. Carbo-loading, so the logic goes, will help you store energy reserves in your muscles.
But now sports scientists are reconsidering the need for endurance athletes to consume foods that are high in carbohydrates before they partake in endurance sports.
Carbo-loading is based on science, which says our bodies need carbohydrates to carry out high-intensity exercise. Stored as glycogen in muscles and liver, carbs offer a fast and readily available source of fuel, so before a big run, swim or bike you need to "load up".
Starches like rice and potatoes - are bad when consumed in excess, but used in moderation can help control one's weight
However, our carb tank is finite. "Our untrained bodies are only designed to carry enough energy to sustain around 90 minutes of moderately intensive exercise," says Dr Duncan Macfarlane, a sports physiologist and associate professor at University of Hong Kong's Institute of Human Performance.
"While you can train your body to store more glycogen … you need to eat during the race to boost your carbohydrate metabolism. That's the type of exercise when you are working so hard that you cannot hold a conversation at the same time."
Yet if you've depleted your glycogen levels, you will become tired and slow down. You can't perform at a high intensity for an extended period without muscle glycogen; you can supplement your stores, but can't do it quickly enough to keep up a fast pace.
In a marathon, reaching this stage of fatigue can mean "hitting the wall". But it doesn't have to mean your race is over and you have to stop.
Luckily, your body has more than one source of fuel, as it also has a conveniently large fat tank. Fat is surprisingly good as a source of energy as it has more calories per gram - nine - than the four in carbohydrate. What's more, you have enough fat stores in your body to run from here to the Great Wall of China - and back.