Find out how to fuel for a half marathon with this beginner’s guide to pre-, mid- and post-race nutrition from Science in Sport…

Having an optimum fuelling plan for those 13.1 miles could help you smash your PB – here’s how to fuel for a half marathon, with the help of Science in Sport.

Half marathons come with their own unique challenges, especially if it’s the first time you’ve raced at this distance. You may have put in plenty of running time preparing for the event, but getting your nutrition right is as crucial to your success as all that endurance training.

To ensure you get your nutrition on point before, during and after the event, the endurance nutrition team at Science in Sport – world leaders in endurance sports nutrition – have put together the following blueprint for race-day success.

Load up

Carbohydrate loading – maximising the glycogen you have stored in your muscles and liver – is a well-established pre-race practice among endurance athletes. (Research suggests that 10-12g of carbohydrates per kg of body weight for around 36-48 hours before an event works best.)

You may not need to load up so much for a half marathon, but you don’t want to get to the start line in a carb-depleted state either. To prevent that, ensure your meal choices contain a good level of carbs – porridge, pasta, rice and potatoes are all good sources – in the days building up to the race.

Rise and shine

On race day, ensure you leave enough time between your last meal and the start of the half marathon – ideally around 3-4 hours.

Your pre-race meal should contain around 140-330g of carbohydrates and, most importantly, it should be a meal you are familiar with – having tested it in training.

Runner running through quiet city streets taking science in sport energy gel

Carb boost

30-60 minutes before the race start, you can take on an additional energy boost. Sipping on a carb/electrolyte drink – such as the SiS GO Electrolyte powder, or having a gel 30 minutes before the start (like SiS GO Isotonic Energy Gels) will provide some extra oomph.

If you’ve been used to caffeine in training, then having a SiS GO Energy Gel with Caffeine can help give an additional kick pre-race.

Finishing formula

If you’ve correctly fuelled the day before the race, your body’s energy stores should be sufficient for between 60-90 minutes of exercise. If your estimated finish time is over 90 minutes, then you will need to think about taking fuel on board mid-race to prevent fatigue.

So, how to fuel during the event is highly determined by your predicted race duration.

Take on fluids

Ensuring you’re properly hydrated at the start line and during the race will combat the loss of fluids due to sweating. Even slight dehydration – as low as 2% – has been shown to affect physical performance by as much as 20%. Taking on electrolyte drinks, especially if your estimated finish time is over 2 hours, will help keep you in a hydrated state throughout.

How to fuel for a half marathon

The SiS table below is a useful guide to know what fuelling to take on – and when – depending you your estimated finishing time…

Estimated finish time Fuelling guidance Example products
60-90 mins ·       If you’ve fuelled well prior to the event, you may not require extra fuel.·       Though, if you prefer to take something on, an energy gel with caffeine could be beneficial.

·       This could be taken between 30-45 mins into your race (the halfway point).

SiS GO Energy + Caffeine (only use caffeine supplements if you are used to them in training)
90-120 mins ·       Ideally, you would take on a small amount of fuel to try and maintain blood glucose and prevent fatigue.·       Around 30-60g of carbohydrates per hour would be recommended.

·       This can be something as simple as a single Beta Fuel Gel or Chew or a few of GO Isotonic Energy Gels.

SiS GO Isotonic Energy GelsSiS Beta Fuel Gels

SiS Beta Fuel Chews (a more solid food option)

120 mins + ·       For longer durations over 2 hours, you may want to consider taking on around 60-90g of carbohydrate per hour.·       Beta Fuel Gels and Chews are great for longer durations, as they contain a higher level of carbohydrate. Same as above but also consider SiS GO Electrolyte powder if you are carrying your own hydration, to ensure you have carbohydrates but also electrolytes.

For further nutritional advice for long-distance running, or to discover the range of endurance sport nutrition available from Science in Sport, visit


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