What to eat before a marathon: what does science say and how to use it in practice?

Nutrition is without doubt just as important an aspect of preparing for a race as training itself; unfortunately many athletes usually do not give it enough attention. In a marathon, though, good or bad nutrition can decide whether you finish the race in your dream time or, in the worst case, do not finish it at all.

Athletes whose race did not go as they imagined often blame the failure on nutrition: they ran out of energy, they were dehydrated or they had digestive problems. Very often the reality is that athletes take in far too much energy and fluid, or on the contrary very little.

Another common mistake is trying out new products that the athlete has not tested in training. In this article we will give you the basic knowledge you need for a successful nutrition strategy and for getting through a marathon in your dream time without any problems.

In this article you will learn

• Why nutrition is key to a successful marathon
• The role of carbohydrates and the importance of topping them up
• What carbohydrate loading (carb-loading) is
• How to get breakfast right on race day
• What to eat and drink just before the start
• Nutrition and hydration during the race
• The importance of caffeine for performance
• How to prevent dehydration and digestive problems
• Why you should train your nutrition strategy too

Why is nutrition so important for a marathon?

Marathon times range, depending on physical fitness, from 2 to 6 hours. The current record for men is held by Kelvin Kiptum at 2:00:35 and for women by Tigist Assefa at 2:11:53. Energy expenditure over these 42.195 km ranges between 2200 and 3200 kcal, with body weight the main factor. Interestingly, energy expenditure over this distance is almost unrelated to pace! There is a simple reason for that. A runner who burns half as many calories per minute as a faster competitor will be running for that much longer – and the resulting energy expenditure will therefore be very similar.

What problems might you come across during a marathon?

Incorrect nutrition can lead to hypoglycaemia (a lack of sugar in the blood) and the runner then barely walks to the finish, weakened and with heavy legs. Even if a low sugar level does not show up immediately, the supply of energy to the muscles may be insufficient, which has a negative effect on performance.

In warm conditions dehydration may be added on top – fatigue, headache and confusion are common consequences.

And the third common problem is digestive trouble. On the course we often see runners vomiting at the side or rushing towards the portable toilets; such is the reality of the marathon for runners who do not give marathon nutrition enough attention.

How can you prevent these problems and increase your chances of a great race?

Besides being well trained and rested, marathon performance is affected by four key nutritional factors:

1. Enough energy stores to get through the marathon:

   • enough muscle glycogen

   • enough liver glycogen

   • topping up carbohydrates continuously during the race

2. Correct hydration
   Preventing dehydration during the race, but also avoiding an excessive fluid intake. This is fundamental above all in the heat.

3. Minimising the risk of digestive problems
   Some runners are lucky and these problems pass them by. Most, though, face them to some degree, and that is why nutrition needs to be well tested and adapted.

4. Food supplements – in moderation
   Apart from sports nutrition such as energy gels, drinks and bars, the greatest acute effect on performance will come from caffeine, which is why we will look at it later in the article.

Carbohydrates as fuel for performance

The body uses two main sources as fuel: carbohydrates and fats.

• Fats are the primary source of energy at low to moderate intensity, that is, in the aerobic phase.
• Carbohydrates, on the other hand, have the main say at moderate to high intensity, since they can supply energy to the body much faster.

For this reason carbohydrates are the main source of energy during exercise, while fats find their main use over longer distances at low intensity.

The body has stores of both fuels, but the store of carbohydrates is considerably smaller than the store of fat. Even the leanest athlete has enough fat stored to get through the longest races at low intensity. By contrast, the store of carbohydrates in the form of glycogen in the muscles is usually 500–800 g and in the liver roughly 80 g – which is enough for 2–3 hours of intense activity.

Many marathon runners know the term “hitting the wall” – the moment when the body runs out of its carbohydrate stores, usually between 28 and 32 km. The body is then left with fats alone, which means that the intensity of exercise cannot be maintained unless you take in more carbohydrates.

There are, however, several simple strategies for preventing this moment: starting with full glycogen stores and topping up energy regularly during the race – with drinks, gels or food.

We also sweat while running. It is a fundamental process that helps us regulate body temperature. Without sweating we would quickly overheat, in the same way that a car engine would overheat without a cooling system. If the loss of fluid is too great, it starts to have a negative effect on the way the body works. Cardiovascular strain increases (heart rate, for example), the ability to regulate temperature gets worse and the risk of digestive problems grows too.

That is why it is important to drink enough to prevent these large losses. Smaller fluid losses are fine and can sometimes even be an advantage.

This means that in the weeks before a marathon and during the race itself we should ensure three key things:

1. Enough energy in the form of muscle glycogen

2. Enough energy stored in the liver as liver glycogen

3. The right level of hydration throughout the race

Carbohydrate loading (carb-loading)

To start the race with full glycogen stores, it is important to increase your carbohydrate intake one or more days before the race, ideally combined with a reduction in training load. This process is known as carbohydrate loading. Careful, though, this is not about overeating – just about replacing part of your protein and fat with a larger amount of carbohydrates. Suitable foods we can recommend are: pasta, rice, potatoes, bread. The extreme diets of the 1970s are not needed.

Breakfast on race day

Breakfast is the basis; in the morning after a night the body has almost exhausted its stores of liver glycogen, because it used them up during sleep. The liver helps to keep your blood sugar level up during the race – breakfast is therefore absolutely fundamental for replenishing it. A suitable breakfast contains 100–200 g of carbohydrates roughly 3–4 hours before the start.

Athletes prone to digestive problems should avoid foods high in fibre, fat and protein. Sensitive individuals can try lactose-free dairy products or leave them out altogether to be safe.

Suitable sources of carbohydrates on race day

• White rice

• Corn or rice cereals

• White bread, bagels without seeds

• Pancakes

• Cooked vegetables (without seeds), boiled potatoes

• Ripe bananas

• Cooked fruit, purée, fruit pouches

• Rice cakes, honey, syrup

• Juices without pulp

Nutrition just before the start

15–30 minutes before the start it is a good idea to top up your liver glycogen stores – it is recommended to take in 20–30 g of carbohydrates (80–120 kcal) and 90–180 ml of water. The carbohydrates start to be absorbed and are used mainly in the first kilometres. Gels or energy chews are popular, but here too the rule applies: practise it in advance.

The ideal option is to use the pre-workout drink hyve Endurance pro, which contains 30 g of carbohydrates per serving in a glucose to fructose ratio of 2:1. This ratio allows you to take in up to 90 g of carbohydrates an hour. However, do not try to reach such an amount of carbohydrates in a race; you need to train for it for several weeks in advance in order to avoid digestive problems.

Nutrition during the race

Nutrition in a marathon requires some planning. It is important to find out what refreshments will be available on the course and to create a plan that takes into account what you can take from the aid stations and what, on the other hand, you have to carry with you. For longer races your target carbohydrate intake should be higher than for shorter ones. In races lasting longer than 2 hours athletes can benefit from taking in roughly 60 grams of carbohydrates an hour. But do not, under any circumstances, try this approach for the first time in the marathon itself! You should build up to this intake gradually during training. Your digestion will quickly get used to it.

Which foods and drinks you use for this is individual. 60 g of carbohydrates an hour can be covered by various combinations of water, sports drinks, gels, chews, bars or ordinary food. In recent years some elite marathon runners have been taking in 90 g of carbohydrates an hour or more. There are even reports of runners who managed up to 120 g/h. Such a strategy, however, requires careful preparation; without it, it could cause problems. The key is to choose the right types of carbohydrates and to practise everything repeatedly in training for several weeks before the race. If you have not done that, it is better not to try this strategy.

Tips:

• Eat before an aid station where there is water.

• Drink at least a few sips of water with every gel or mouthful.

Solid food

Energy bars often contain 30–60 g of carbohydrates, but also fat, fibre and protein – which can slow down digestion. Versions with a low content of these components are therefore ideal. Bars help against the feeling of an empty stomach, but they tend to be harder to digest while running. Gels or chews are more suitable for some athletes.

Gels and chews

Gels: small volumes with a high carbohydrate content (20–25 g); versions with caffeine also exist. Chews: a compromise between a bar and a gel – easy to chew, portions of about 6–10 g.

Drinks with carbohydrates

Hypotonic drinks
Hypotonic sports drinks usually have a concentration of 6–7 %, i.e. 60–70 g/l. A 600 ml bottle therefore contains about 35 g of carbohydrates. It also contains sodium and other electrolytes, which help with hydration.

Hypertonic drinks
These drinks are designed to contain considerably more carbohydrates than ordinary sports drinks. They still supply fluid, but their main purpose is to top up energy. These drinks are especially useful in longer races, when it is not realistic to carry a larger volume of fluid with you but you still need to take in enough carbohydrates. Some of these drinks contain up to 90 grams of carbohydrates in a single 500 ml bottle.

Caffeine and performance

Caffeine increases performance – about 3 mg/kg of body weight is recommended, which is 200 mg for a 70 kg person. It is absorbed within 30–90 minutes, but it also works later during the race. The best timing? That is individual. What matters is not to exceed a daily dose of 400 mg.

An overview of the caffeine content in common products:

• Gels: 25–50 mg

• hyve 100% Natural caffeine: 50 mg/capsule

• Cola (355 ml): 40–50 mg

• Energy drink (250 ml): 50–100 mg

• Espresso: 80–100 mg

Dehydration

Dehydration is another common cause of fatigue in a race. We regulate body temperature by sweating – the higher the pace, the more heat and so the more sweat. If we lose too much fluid (more than 3 % of body weight), performance drops. To prevent this we recommend the hydration drink hyve Hydration pro, which hydrates the body effectively and tops up energy during exercise. To prevent dehydration, it is important to start the race well hydrated and to keep the right level of hydration throughout the run.

Hydration strategy:

• Before the race drink at least 500 ml of fluid about 2 hours before the start.

• Watch the colour of your urine – it should be pale.

• During the race drink enough to lose at most 2–3 % of your weight.

• For slower runners it is enough to “drink to thirst”; faster runners should have a plan.

• Towards the end of the race the stomach may absorb less – so hydrate properly right from the very start of the race. It makes sense to use the first part of the race, when the digestive tract works without problems, to take in both carbohydrates and fluids. Do not drink excessively and use common sense; there is a risk of hyponatraemia (overhydration). A slight loss of weight (1–2 kg) at the finish is normal.

If bloating or a feeling of a “full stomach” appears during the race, slow the pace slightly and give your body time to process the fluid.

Athletes who want to prepare really thoroughly can measure in training how much they sweat in given conditions and adjust their fluid intake accordingly. Gaining weight during a race is a clear signal of excessive drinking, which can lead to dangerous overhydration. Do not forget that proper hydration starts in the days before the race.

Practising your nutrition is just as important as running training itself

Whoever is prepared is not surprised. Nutrition is not something you start practising at the expo the day before the race! Start 6–10 weeks in advance. Your preparation should also include “nutrition sessions”. During easy runs, recovery runs and interval sessions you can train in a low-carbohydrate, higher-fat mode; on long runs, on the other hand, typically on Sunday for many runners, simulate the race and practise your plan for topping up energy and fluids. It is a good idea to practise breakfast itself too.

The three most common nutrition mistakes in a marathon

1. Having no plan.
   Setting off on a marathon with the idea “I will drink when I am thirsty and take something at an aid station if I need it” is a gamble. It may work out, it may not. If you have invested dozens of hours of training in your preparation and planned every run, why should you not also plan your energy and fluid intake? That is exactly what will significantly increase your chances of success.
2. Sticking to the plan too strictly.
   Some runners do have a plan, but they hold on to it far too firmly. A plan is important, but that does not mean it cannot be changed. When the weather is warmer than usual, you may need more fluid. When digestive problems appear, it is fine to reduce your intake temporarily.
3. Trying new things.
   Many runners get excited at the expo the day before the race, buy new gels or drinks and then try them for the first time in the race itself. That is a recipe for problems. Stick to what you have tested in training and know works for you. The marathon is not a day for experiments.

The best tips to finish with

• Do not try new products on race day.

• Train with the products you are going to use for at least 6 weeks in advance.

• Listen to your stomach – if fluids are not being absorbed, slow down.

• Start the race hydrated – drink enough a day or two before the race as well.

• Plan your breakfast in advance. Do not let the hotel's offering catch you out.