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How To Fuel Before, During, And After An Ultra Marathon

ultra marathon running race how to fuel nutrition hydration

Fuelling for an ultra marathon is possibly one of the most difficult areas to get right and one of the main reasons runners drop during distance racing. As runners, we tend to focus on the obvious: our physical training and endless kit choices. However, fuelling and mindset are two really important areas which can be neglected.

This year I am competing in the Centurion Grand Slam: a series of four 100-mile foot races in May, July, August and October. I have completed this distance twice previously but doing all four within a year has been a very different experience and a massive learning curve. Time of year, trail conditions, course and temperatures all play a big part in the fuelling strategy.

Pre-Race Fuelling

Pre-race fuelling is the easy part. Contrary to popular opinion, 'carb-loading' shouldn't be eating everything in sight the night before the race. Instead, you should gradually increase your carbohydrate intake in the week leading up to the race in order to get your body used to storing more fuel.

There is a limit to how much fuel can be stored in the muscles. Most sources estimate 400gm or 1600 calories, but each individual is different. Personally, my diet does not change too much the week before a race. I tend to eat little and often with 6 smaller portion meals which are easier to digest than opting for 3 larger meals which will just leave me feeling bloated and uncomfortable. I also ensure I am hydrating well.

I tend to increase my carb intake and reduce my consumption of fruit and vegetables; the less fibre the better as this will prevent gastric issues while you are running. Normally I love spice in my food, but on endurance events your digestion system will be taking a back seat as all energy focuses through the big movement muscles, therefore it is best to stick to plain and bland foods to avoid stomach upset.

I am very much a creature of habit on the “final dinner” which is always pasta with fresh tomatoes, garlic, basil and olive oil. I eat dinner 2 hours earlier than normal, followed by a sandwich an hour before bed. You want to allow time for your dinner to digest before bed, so when you have to get up for an early start, your body is ready to complete the digestion process – meaning no last minute toilet queues!

Key points:

  • Don't eat everything in sight the night before the race. Carb load for an entire week before the race by eating little and often and gradually increasing your carb intake.
  • Reduce or eliminate entirely your intake of fruit and vegetables. Less fibre will prevent an upset stomach or gastric issues/emergency toilet stops.
  • Avoid spicy foods, stick with plain and bland foods.

ultra running marathon race endurance trail nutrition hydration fuelling

Race Day Fuelling

If you can eat breakfast, keep it light. If nerves get the better of you and you feel like you can't eat: don’t worry.

For marathon distance, gels work well for most people and are a convenient choice, however on the longer distance you really need to be able to eat “real” food. Checkpoints are usually stocked with a variety of sweet and savoury foods and on longer distances, the later checkpoints will even provide hot food and drinks.

It is worth checking your race information, which usually lists the type of foods and drinks you can expect. If you have specific dietary requirements, you may need to be more self-sufficient – I am vegan so this applies to me. It is also worth carrying emergency supplies on your person.

Start fuelling early and take plastic bags with you so that you can take away foods from the checkpoints to eat while you continue to run. You may need to slow your pace to allow your body to digest the food properly. 

Some ultra marathons and most races beyond 100km will allow access to drop bags and crew at designated points so ensure you pack some food into your drop bag (in addition to extra kit). It is difficult to decide before the race what you will feel like eating, but get some of your favourites in there – it’s always nice to have a special treat to look forward to.

fuelling for running marathon ultra race nutrition hydration


Nausea is one of the most common things that prevents runners from finishing ultra marathons. If you are feeling or being sick, you are losing energy and hydration – lack of both will cause the body to dip mentally and physically. As difficult as it may be, you need to keep eating and hydrating. If you feel nauseous, try slowly chewing crystalised ginger as this can settle the stomach. Also try chewing gum.

Hot Weather

Weather conditions also affect your fuelling strategy. Extreme heat can make it difficult to eat and you might have a tendency to drink in excess which will cause a sloshing effect on an empty stomach. It’s always a good idea to carry some money so that you can buy a cold drink or ice cream, or ask your crew to have some ice and cold drinks available.

Night Races

If your race takes you through the night, the body will find it difficult to digest as it’s simply not used to eating through the night. Keep eating little and often and if there are hot drinks available from checkpoints and crew take advantage of this; it will also keep you warm.

Sodium Replenishment

Replenishing sodium is something you should have practised in your training. As you sweat, you will lose body salts and minerals so over long endurance events it is vital to replace as you go along, otherwise you may suffer nausea and muscle cramp. There are lots of products on the market in tablet and liquid form – get to know your body and practise in training, and carry additional in your hydration vest on race day. Also bear in mind seasonal factors; it’s easy to tell you are sweating in the height of summer, but you will also be working up a sweat in the middle of winter.

Post Race Fuelling

Race completed: permission to eat the world granted! Do not be surprised if in the first 24 hours you have no appetite – your digestion system has to re-boot and this generally requires sleep. I find that after a 100-mile ultra marathon I sleep for a few hours, wake up hungry, eat a little, then sleep again – this is the first 24 hour routine.

Once your appetite returns, make sure you fuel little and often. It’s natural to feel fatigued between meals as your body runs out of food. The best advice on post ultra-fuelling is to listen to your body. Ideally, you require all food groups, but you may crave protein as the body will want to repair muscles. I tend to want protein and masses of fruit and vegetables as my body craves the nutrients from the vegetables. Dependant on the distance of your ultra, recovery will take from one week to usually six weeks for a 100-miler. A spa treat to relax both body and mind the week after a tough race is a great idea. Look after your body – it has served you well!

About the author: Sheila Rose is a personal trainer, ultra runner and Sundried ambassador. 

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