Your Marathon Fuelling Guide

Training, recovery, and nutrition are probably the most important aspects when it comes to your marathon or any athletic performance. Over the years, we are seeing a greater focus on performance nutrition. This trend may have been the result of athletes experiencing DNFs, gastro-intestinal (GI) issues, hitting the wall, dehydration, overhydrating, cramping, overeating, or not eating enough, etc. Or perhaps they realised the incredible performance potential from optimising their fuelling and hydration during training and racing. 

There have been many trends over the years on how best to fuel from low fat, high fat, low carb, fasted, etc. There is no right or wrong way to fuel and hydrate. The most important takeaway from this read: fuel and hydrate during your races with what you have tried and tested during training and stick with what works for you.

How good nutrition can support your marathon

A marathon is long no matter which way you look at it. For those super humans, it can take around 2 to 3 hours. For the rest of us, anywhere up to 6 hours.

An element in determining the level of detail in your nutritional plan is to consider if you want to perform at your best, or if you just want to finish with no time allocation. 

If you are simply keen on finishing with no time allocation, then you may get away with little to no nutritional considerations. If you are walking for the most part and if this means low intensity for you, then you can probably eat and drink almost anything to get you through the distance, and without any concerns of gastrointestinal (GI) issues. 

Given that we store around 100,000 calories of fat and it takes around 3,000 calories (carbohydrates and fat) to complete a marathon, it’s fair to say you will likely have enough energy stores to fuel your marathon - at this intensity, fat will be your primary fuel. 

If however, you wish to perform at your best and your intensity reaches moderate to higher levels, then you would be wise to devise a well-rounded nutrition plan.

Fat and carbohydrates are our main fuel sources. Think of fat as the slow burning diesel and carbohydrates as the high octane stuff. Fat requires more oxygen and energy to be broken down and used as fuel than carbohydrates. Fat is usually the main fuel source for efforts of low to moderate intensity or anything up to around 70% of our maximum heart rate.

We store carbohydrates in the form of glycogen in the body, with the muscles housing the largest amount of approximately 500-700g, the liver about 100-160g and smaller amounts in other parts of the body such as the brain, heart, kidneys, and some in our fat cells. Low levels of glucose float about in our blood making it ready for uptake mainly by the brain. Our total internal glucose and glycogen levels are largely dependent on an individual’s body size, mass, fitness, and diet. When muscle glycogen stores get low, the liver starts to release its stores to satisfy the needs of our working muscles.

How many carbohydrates and what type to consume?

Consuming 45g to 60g of carbohydrates per hour during your marathon is a good place to start to prevent your energy levels from dipping too low. This amount is also well tolerated by the gut for most people. Given an energy gel is usually 20-30g or carbohydrates per serving, it would mean consuming 1 to 2 gels within 60 minutes. Remember, this is over a 60 minute period and not on the 60 minute mark. Consuming the energy gels gradually over the hour tends to sit better in the gut for most athletes.

It is worth noting that almost everyone gets a sensitive gut when doing longer distances such as marathons. The key is to minimise this uncomfortable state to a level that allows you to still consume what you need to perform.  

It does not matter where your source of carbohydrates come from. What is important is being aware of what you can handle and digest. Bananas are a great natural source, but they can take longer to digest and sit in the stomach for longer. Gels, chews, drink mix, etc are all very effective ways to get your carbohydrates in and they usually have other ingredients such as electrolytes that bring additional benefits. Whatever source of carbohydrates you choose, just be sure to trial them during training.

If you are after more details, then this article focuses on fuelling guidelines before, during and after your marathon. In addition, we show you how to take on more carbohydrates to improve performance. 

In summary: consuming carbohydrates during your training sessions and marathon can enhance both your physical and mental performance, reduce the chances of bonking and DNFs. The total amount of carbohydrate required depends on the duration and intensity of your session:

• Sessions lasting up to 1 hour: Up to 30g carbohydrate per hour should suffice.
• Sessions lasting between 1-2.5 hours: Aim for 30-60g carbohydrate per hour.
• Sessions lasting more than 2.5 hours: 60-90g carbohydrate per hour.

Hitting the wall or bonking

When we hit the wall or bonk, it means our muscle glycogen (the primary fuel source during moderate exercise at approximately 75% max heart rate and above) gets depleted at a rate faster than it is topped up. Although not completely empty, glycogen levels are low enough to render the muscles ineffective to meet the physical demands. This usually happens around the 32km or 20 mile mark.

Yes, while your body is likely to switch to burning fatty acids at this time but burning fat require about 2.4 times more oxygen compared to burning carbohydrates. While the burning of fat yields a tremendous amount of energy, it’s not the high octane stuff needed to keep you going at moderate to more intense efforts. As a result of switching to fat fuel, your body will slow down to facilitate this conversion.

Glucose is a critical energy source for the brain. It can consume up to 60% of the glucose floating around in the blood. If you aren’t fuelling well in the marathon and muscle and liver glycogen and blood glucose levels drop too low, you could enter a hypoglycaemic state (low blood sugar), therefore impacting your mental and physical state leaving you feeling dizzy, lightheaded, confused, and grumpy.

This can result in poor choices, or even the simplest of tasks seem complex and frustrating during your marathon. This low energy state may result in a DNF in some cases, as you practically run out of energy.

Carb Loading 

Carb loading is about maximising your carbohydrate stores, so you have a full tank of energy come race day. There have been many carb loading protocols over the years. Keeping it simple, the latest recommendation is to consume 10 to 12g of carbohydrate per kg of body weight (g/kg) per day, for the 36 to 48 hours before your marathon. For a 60kg (132 lb) athlete that’s 600g to 720g of carbohydrates per day. Training volume reduces during this part of the mesocycle so it is likely you will consume more carbohydrates than you need on the days leading up to your marathon.

For some this will feel like overeating and getting in that many carbohydrates may feel impossible. However, you could consider taking your carbohydrates in liquid form such as carbohydrate drink mixes or fruit juices, pizzas, white bread with jam sandwiches, pancakes and topping up the rest with a handful of sweets. Aim to keep protein, fat, and fibre levels low, as those nutrients will fill you up and restrict carbohydrate intake. You’re only doing this for a day or two so enjoy the sweets guilt-free. Remember, this is about saturating your glycogen stores and not a get out of jail free card to eat whatever whenever. You still need to be strategic in food selection. 

It's worth noting carbohydrates retain roughly three times as much water, 1:3 ratio. Extra carbohydrates and extra water means extra weight. However, this extra weight is usually offset by having additional energy and water, which you will need and use during your marathon.

Train Your Gut

You can train your gut to take on more and different types of fuel and liquids just as you can train your muscles to go harder for longer. The key is to practice your fuelling and hydration during training.

Gastrointestinal (GI) issues are very common with athletes and can result in stitches, stomach cramps, reflux, stomach fullness, vomiting, bloating, etc. Taking in fuel and hydration in small amounts during training gets your body used to taking in these nutrients on the go, as this is when the stomach gets sensitive. Small and often is usually the best approach when consuming during exercise.

It's important to note that the higher the intensity, the harder it becomes for the body to digest as most of the energy and blood is directed to working muscles. Anything consumed may sit in the stomach and take longer than what is desired to digest and get sent to the working muscles.

A good place to start is to eat something before your runs to ensure you start your training or marathon properly fuelled. You could try 2 to 3g of carbohydrates per kilogram of body weight, 2 to 3 hours before you run. For a 60kg runner, this is about 120g (480 calories or 3.5 slices of raisin bread) – 180g (720 calories) 2 to 3 hours before your run. If you are within the hour of your run or have never been able to stomach anything before your run, especially if it’s an early morning effort, you could try half a banana, table spoon of honey, a few dates, etc. Start with something small that has a high carbohydrate source and is easy to digest and go from there.

Training your gut is somewhat easier on the longer slower runs, as intensity is lower, and you can handle your nutrition easier with less fumbling. Each week, slowly increase your dosage until you feel you’re getting enough energy and hydration or are feeling a little full. Stick with that amount for another training session or two, then up the intake again. Repeat this process until you are happy with the amount of fuel and hydration you are taking in. This means you are not feeling low on energy, heart rate does not drop too low on longer efforts, you stomach is not feeling too full, sloshy or bloated, etc. If you feel it gets too sloshy in your stomach or you’ve taken on a little too much, then cut back on the next session. It’s all about trial and error and can take several weeks to get right. The more you practice it in your training, the quicker you will learn what you can take on board and when.

Remember to try different sources of fuel and hydration as your gut may prefer more liquid forms than solid forms when exercising.

Ideally, you want to nail your nutrition strategy at least 10 weeks before your marathon. Put another way, 10 weeks before your marathon you should not be changing your nutrition strategy – it should be well in place and being practiced during training. Fuelling well does boost performance as you can see from this study. So, train that gut. 

Caffeine

Previously thought as a powerful diuretic, caffeine is now reclassified as a mild diuretic. Caffeine effects are very personal and while some can handle the upper end of the recommended dose, there are others that can experience the impacts of caffeine at a very low dosage.

Caffeine has been shown to stimulate the central nervous system, improve performance and focus, and reduce perceived exertion in some people but not in everyone. Others, however, can be extremely sensitive to the drug and should therefore be used sensibly. If you plan on using caffeine, then trying it during training is essential to see how it affects you, your tolerance and sensitivity levels to it.

Currently the dosage recommendation is 3 to 6mg per kilogram of body weight (mg/kg) (1.4-2.7mg/lbs). For a 70kg / 150lb athlete that works out roughly to 200 to 400mg of caffeine. 400mg of caffeine roughly equates to 2 espressos.

Caffeine sources come in all sorts from gummies, gels, tablets, etc. It can take up to 60 minutes for caffeine to digest and take effect. If you plan on using caffeine, then consider the timing of your intake. If you want to use caffeine to get you ready for the start line, then consuming it around the 60 minute mark before the gun goes off is likely the ideal time to take it. Again, its effects are very personal.

If you are going to take caffeine towards the end of your race, remember that its half-life is around 2 - 5 hours. Meaning 5 hours after you’ve consumed your dose you will have half that dose still floating around your system. This residual amount floating about can negatively impact sleep. This is something to consider if you are wanting to get some sleep after your marathon or get to bed early before your marathon the next day and you’ve had a coffee of two.

Fluid intake

Two ways that can guide us to take on enough fluids are drinking to thirst and following a planned strategy. Drinking to thirst works most of the time for most people but as conditions get hotter, the race gets harder and longer, our thirst mechanism can become less effective at reminding us of when to drink. That’s when a planned strategy can work nicely, for example, drinking 2 cups of plain water at every aid station whether you feel thirsty or not.

Aim to ingest a regular supply of fluids regardless of the plan you choose. You are not looking to replace your entire sweat loss, which you can work out here but rather to replace enough fluids to prevent you from going into severe dehydration or hyponatraemia.

Getting your fluids and fuel in early is usually a good idea as your gut becomes more sensitive later in the race. This way you get more fluids on board earlier and should you experience gut issues, then at least you have something to keep you going a little longer or until the gut settles.

Adding electrolytes, in particular sodium, can help the body absorb and retain fluids. This is why many athletes take an extra pinch or two of salt in their meals a day or two before the race. The sodium in drinks can also keep you thirsty so you keep drinking. This is your thirst mechanism at work here. 

During your marathon, common sense can be rare with so much going on around you and adrenaline pumping through your veins. When it comes to fuelling or hydrating, it’s usually better practice to pay attention to what your body is feeling. If you are feeling a little bloated or hear/feel fluids sloshing around, then cut back on your intake and slow your pace to allow the fluids and fuel to empty from your gut. If you’re feeling low on energy, then gradually top up your fuel. As mentioned previously, taking on fluids and fuel gradually is the preferred approach, unless you have trialled taking on larger amounts during training with no adverse effects on how your gut is feeling.

Dehydration

When we exercise, we expel fluids mainly through sweating and exhaling. Sweating is our body's way of keeping cool. Increasing our rate of work and the temperatures in which we exercise can mean our breathing rate increases, core temperature rises, and the body works very hard to keep cool by sweating more. When our sweat rate is greater than our fluid intake, we go into fluid deficit and we get dehydrated.

Dehydration reduces blood volume - essentially our blood gets thicker. This means the heart must work harder to deliver oxygen and remove carbon dioxide from the muscles. This loss in cardiac efficiency means the rate of perceived exertion goes up and we are likely to slow down. 

Fluids do not necessarily improve performance but rather can prevent the decline in cardiac efficiency and cardiac performance, which in turn can hinder performance.

The lack of fluid intake can indirectly impact performance on runs longer than 60 minutes. Shorter runs may not develop enough dehydration to impact performance. Longer runs however, are usually more important to monitor fluid levels, reduce dehydration and to prevent any drop in performance.

While it is never advisable to replace all our fluid loss when exercising, it is essential to keep our dehydration levels in check.

Losing up to 2 - 3% body weight through sweat may not have much of an impact on your performance but any higher than this and you may find your performance being impaired. This is of course very individual, and some athletes have gone up to +6% dehydration and still performed well. Drinking 200ml – 800ml per hour of fluids is usually tolerable and the recommended bandwidth. Women tend to tolerate slightly lower levels than men but trialling your intake during training should give you a good idea at the levels you can handle. The faster you’re going, the less you’ll be able to digest.

Having a Plan 

Starting your marathon well hydrated can help both reduce and delay dehydration levels. You can start hydrating 24 hours before the race starts. Keep it simple and just add 500ml water to your daily intake. You can consume a drink mix that contributes to your carbohydrate intake and has all the electrolytes you need, or add salt tablets to your water or even easier, add a pinch of salt to your food or drink. The sodium will help retain the water in the body.

Before the marathon

As with all hydrations and fuelling ideas you want to make sure you’ve tried and tested these before race day. Remember – nothing new on race day! You want to practice reducing the chances of dehydration, while avoiding overfilling the gut. It’s always easier to top up as you go than get rid of what is already in the gut.

From 1 to 4 hours before the start, you can probably take in anything from 2 – 7ml of fluids per kilogram of body weight.

Current research on fuelling before the race suggests you can consume 1 – 4 grams of carbohydrates per kilogram of body weight 1 – 4 hours before you start. So, if you weigh 60kg, that’s anywhere from 60 grams 60 minutes before to 240 grams 4 hours before the gun goes off.

The table below sums all this up for you. 

 

 

You may have race nerves and a sensitive gut on race morning so you may not be able to handle what you usually can on a typical training day. Therefore, go with smaller amounts to start and see how you feel.

During the marathon

Your number one priority is to manage your dehydration levels. Fuelling and electrolytes come after.

Most, if not all, large scale marathons are required to have aid stations. Sometimes the food offerings at these stations look tempting but unless you’ve tried what’s on offer during training, it’s probably best you avoid them unless necessary.

Nutrition offered at the aid stations can have higher levels of fat, fibre, etc. than what you are used to when training and consuming them during your marathon may result in GI issues. You could always search the event website, contact the race organiser beforehand or read the athlete brief to see what will be offered on race day. That way, you can get your hands on the same nutrition and practice fuelling it during training.

If you have no choice and need to consume what’s on offer, then start small i.e., take on less than what you normally would and see how you handle it. If no GI issues present themselves, then you’re in a good place to probably continue with the fuel and hydration sources on offer.

At my last race, they had snake gummies on offer. Who wouldn’t want to eat a handful of snake gummies when you’re low on energy and 60km into a run? Two snakes are the equivalent to about 1 gel. So, while they can be very tempting, they can very easily and unintentionally throw you well over your fuelling intake requirements. 

You could run with a hand flask that has a drink mix topped with water or a flask with a very high concentration of drink mix chased with water from the aid stations. The drink mix option tends to carry more electrolytes than other options, but you will need to carry the drink mix.

There is no need to carry regular water for your marathon if there are aid stations. Carrying water is heavy and costs energy. Take the cups from the aid stations and remember to thank the volunteers. Pinch the cup at the top to avoid it spilling – keep your shoes dry to reduce blistering.

If you are one for using gels, then you could consider squeezing a few gels into a small handheld flask and top it up with water. You could mark on the flask the amount of fuel you’ll need at certain times of the run. Gels don’t carry a lot of electrolytes so you could add a pinch of salt or add a salt tablet to the flask if it’s needed.

After the marathon

Your marathon is going to be tough mentally and physically. You are likely to feel aches and pains the next day but you can speed up recovery with good nutrition.

Unless you plan on doing another marathon or have another training session 24 hours after your marathon, just head to the post-race nutrition buffet and enjoy the feed. If you do have another training session however, and need to speed up recovery, then taking in 1 to 1.2 grams of carbohydrates per kilogram of body weight per hour after exercise stimulates the highest rate of glycogen synthesis and is an important and effective strategy to quickly replenish your fuel stores for your next session. Do this for the following 2 – 3 hours post-race. For a 60kg (132 lb) athlete that’s about 60 to 72 grams (2 to 3 slices of wholewheat bread) every hour.

Consuming 0.3 to 0.4 grams of protein per kilogram of body weight within the first hour after exercise has been shown to optimize muscle protein synthesis, i.e., repair damaged muscles quickly. Master athletes, however, should look at slightly higher levels of around 30 to 40 grams of protein within the first hour after exercise as the repair process can be somewhat slower.

Consuming 1.5 times the fluids lost will help quickly replace fluids and keep dehydration at bay. If you lose 1 litre of sweat, then drink 1.5 litres of fluids. Chances are the foods you’re eating will have sodium in them, so you don’t need to add extra sodium to your drink. If they don’t, then adding a pinch of salt will work well to help retain the water you’re taking in and balance out your electrolytes. 

Whatever your chosen nutrition strategy is, just ensure you practice it during training. Remember, avoid anything new on race day. There is a good chance your strategy may need changing on the fly. If it does, just stay calm, reassess your current situation, adapt, work with what you’ve got, consume small amounts and listen to your body.