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Christopher Bradley  •  Running Training •  05.05.2022 •  8 min read

How to fuel your marathon

This article is designed as a starting point to decide how to fuel your next marathon. This is not concerned with meal plans in a training block, eating for recovery, or special performance-oriented diets - this is a broad strokes introduction on what to consume and at what frequency to get the most out of your body when it comes to notching that first marathon time or chasing your PB.

The basic science

Your body’s two main fuel sources are fats and carbohydrates. Nearly everyone will be utilising carbohydrates as their main fuel source when racing a marathon, so while being able to metabolise fat is a great physiological adaptation to have, this article will be focusing on using carbohydrates as the primary fuel source. 

Glucose is formed from the breakdown of carbohydrates in our diets and is stored as glycogen in the muscles and liver, but there is a limit to the amount of glycogen the body can store. We have about 60 to 90 minutes' worth of glycogen stored, depending on the intensity at which we are exercising and allowing for physiological differences between individuals.

Laying the foundation

Obviously, eating a really greasy takeaway the night before any sporting endeavour is going to negatively impact your body’s ability to perform to its best. Throw in a fry-up and a milkshake the morning of and you will – without a shadow of a doubt – perform even more poorly. 

How you fuel the night before and the morning of your race will have a huge impact on your performance. Don’t fall into the trap of thinking carb-loading is an excuse to hoover up double portions - you shouldn’t be taking in bigger quantities of food overall, just shifting to a higher percentage of carbohydrates to appropriately fuel the effort you’re preparing to lay down. A high carbohydrate meal the night before a race to top up the body’s endogenous glycogen stores is the best option. Foods such as rice or potatoes are easy to digest and high in carbohydrates. 

Avoid foods high in fats, as fat blocks carbohydrate absorption, and will therefore limit the effectiveness of the high carb meal, and may even cause stomach distress during your race. 

So no, pizza the night before your marathon is not a good idea. 

The morning of the race, ideally a couple of hours before your start time, something like porridge or oatmeal with fruit would be good to top up your carbohydrate stores without overloading the stomach. If you know from experience that consuming milk before a run negatively affects your stomach, switch to a dairy-free alternative. 

It might even be an option to make up a bottle of Maurten 320 to sip, either if you’re pushed for an early start time or you have an especially sensitive stomach. 

The most important thing to avoid is foods high in fibre, as this could well lead to stomach distress in your race.

Keeping the engine running

If you’ve eaten right the night before and in the morning, you should be starting your marathon with between 60 and 90 minutes of endogenous carbohydrate stores, but this won’t be enough for 99.99 per cent of athletes to go and fuel their best showing over 26.2 miles of asphalt. 

This can be where things get complicated…

Have you put down a detailed nutrition plan? Have you practiced said nutrition plan in training?

Typically, most city marathons will have water stations dotted along their course, and some will give out their sponsoring nutrition brand’s products at some of these stations, but three or four gels over the course of three to potentially more than six hours just isn’t enough. And it’s quite easy over the course of a goal event to mentally check out and miss one of these opportunities to refuel.

As early as you can in your training cycle it’s important to experiment with different products and see what works best for you.

Energy gels

Gels are easy to carry, don’t require chewing, and are almost impossible to choke on - an important quality when you’re putting your body through 26.2 miles of concrete as fast as you’re physically able. For these reasons, they’re the most popular way to fuel a marathon, and they’ll be the main focus of this article. 

Most gels contain 20-30g of carbohydrates. Depending on your target time and the intensity you work at during your race, runners could fuel their marathon on as many as one gel every 20 minutes to one gel every 45 minutes. The quicker the race and more intensely an athlete is able to work, the more frequently they will need to take on exogenous carbohydrates (like gels) to sustain the effort.*

One of the most common complaints from athletes about gels is that they get stomach distress. Assuming this isn’t a hangover from the pizza party the night before or the obvious result of a heavy bowl of muesli drowning in rich Jersey milk an hour before the start line, some gels are specifically designed with this in mind.

High 5 and SiS gels are isotonic. They are mixed with the right quantity of water for the absorption of the carbohydrates, and this, coupled with them not being as thick as more traditional gels, can make them a bit easier on the gut. However, they contain slightly less carbohydrates, so for the same effort, an athlete would need to consume more isotonic gels than traditional-style gels. 

Swedish brand Maurten use hydrogel technology in their gels and drink mixes, which enables a smoother transportation of carbohydrates through the stomach to the intestine where the carbohydrates are absorbed, dramatically reducing the risk of gastronomic distress while still delivering a product with a high carbohydrate-to-weight ratio. 

As well as the Gel 100, which contains 25 grams of carbohydrates, they also produce a Gel 100 Caf 100, which as the name suggests, adds 100 milligrams of caffeine, which can reduce an athlete’s perception of effort and reduce pain (depending on an individual’s sensitivity to caffeine). 

Torq energy gels use natural flavourings and have a thin consistency, so while they are able to pack in 30 grams of carbohydrates per gel, they’re still easier on the gut than most gels on the market today. 

Other options

Some athletes prefer to get all their calories mixed with water, so drink mixes like Tailwind, SiS’s Beta Fuel, and Maurten’s Drink Mix 160 are all potentially compelling options to fuel marathons. The only caveat is that you’ll have to think about how to carry your drink in a race, as water and fuel stations won’t be tailored to individuals. 

If you can’t get on with gels, aren’t a fan of drink mixes and want to stick by solid, chewable nutrition, you could try Sport Beans or Clif Bar Shot Bloks. Both are easy to carry, carbohydrate-rich fuel sources. 

Practice makes perfect

The most important thing about fuelling a marathon is practicing in training what you intend to do on race day. It’s far better to discover your body doesn’t agree with a particular product or flavour of gel on a training run than halfway through a race, and the earlier you start practicing your nutrition, the better. You can train your body to take on calories, and fine-tune your plan as you learn what works best for you. 

*It’s important to note that while your body has 60 to 90 minutes’ worth of endogenous carbohydrates, you should start topping them up far, far earlier than this. Once you begin to bonk, it’ll be extremely difficult (perhaps impossible) to come back. If your plan is to take a gel every 45 minutes, take your first gel 45 minutes into the race, if it’s every 30, take it 30 minutes in. Remember that you’re fuelling to sustain an effort, not depleting your reserves and replacing them.

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