Got a big race coming up? You don’t want to knacker all those weeks of sweaty training by eating the wrong things in the days and hours before the event, leaving yourself short on energy, over-stuffed, empty-bellied, or – worst of all – with a twitchy tummy that has you diving into every Portaloo you pass on the route.

Nutrition-wise, the key to sailing across the finish line like a grinning champ is carb-loading. To get the low-down on what carb-loading is, why it’s important, and how to do it, Unbound spoke to Frida Harju, keen marathon runner and in-house nutritionist at Lifesum, a Stockholm-based healthy-living app with over 11 million users.

Hi Frida. So what exactly is carb-loading, and why is it important before a big race? 

“Carbohydrates are made up of sugar molecules, which the body uses to produce glucose. Glucose is then changed into glycogen in the liver and muscles, which in turn provides a great source of long-term energy, which comes in useful during an extensive run.

“Eating carbs before a run improves your endurance, alertness and speed”

“Eating carbs before a run improves your endurance, alertness and speed, all of which will help you perform better in the race.”

How many hours or days before a race should you start carb-loading?

“In the lead-up to a long race you’d be looking to increase your carb intake by about 10% in the days before, in order to have a successful run. It’s also important to ensure that your training is less intense in the final week before the event.

“A few hours before your run, have a balanced but light meal that includes some, but not too much fibre, which can cause stomach problems during your race, so be careful. Oatmeal, a chicken sandwich or whole-grain cereal are good choices.

“Avoid heavy meals at least three hours before the race. And be sure to increase your water intake in the lead up to the big race to ensure that you’re well hydrated before you take your mark.”

What are good foods to carb-load with?

“Complex carbohydrates with low glycemic indices (GI) such as wholegrain bread, pasta and brown rice are the best source carbs, as they provide the muscles and fat tissue with glycogen.

“Porridge is another great carb food, as it contains a high amount of complex carbohydrates, which give you lasting energy by gradually releasing sugar into your bloodstream.

“It’s also advisable to snack often, choosing fruit over unhealthier options. For example, bananas are a great source of fructose, which supplies the body with glycogen – a major source of energy.”

And which foods should you avoid?

“It’s best to avoid foods that could give you an upset stomach. Obviously each individual’s tolerance to certain food types is different but, generally speaking, spicy foods and rich, creamy sauces can disrupt the digestive system or cause heartburn.

“Fizzy drinks can also cause a build up of air in the stomach, leaving you bloated and gassy”

“Also, try to avoid foods with a high salt content such as crisps or fast food, because they can dehydrate you, causing intense thirst and tiredness during your training or run. And fizzy drinks, even those low in sugar, can cause a build up of air in the stomach, leaving you feeling bloated and gassy.”

Should you be concentrating solely on consuming carbs, or also looking to take on proteins and fats and so on?

“Having too much of anything is counterproductive, so don’t just focus on eating carbs. Make sure to eat a healthy and balanced diet in the weeks before a big race.

“Cottage cheese is a great food to have”

“Lean protein, like grilled chicken, is a great food to eat both before and after exercise. Pre-workout, chicken will fill you up and give you energy without leaving you feeling bloated and full. Post-workout, the protein will help your body in its recovery mode.

“Cottage cheese is also a great food to have, as it contains glutamine, an amino acid which is valuable for muscle recovery. Cottage cheese is also rich in calcium, which strengthens your bones and prevents fractures.”

Okay then. Any final words of advice? 

“During the run, you want to stay focused on drinking fluids with a good percentage of carbohydrates, glucose and sodium in them to keep your blood-sugar levels up.

“Be sure to grab a drink of water at every drinks station, but also balance those with a sports drink such as Lucozade or Gatorade to avoid over-hydration – the body’s natural balance of electrolytes is disturbed by too much fluid.”

Ace. Thanks Frida!

The Lifesum app is available for free on iOS and Android