Nutrition and Marathon: What Should Marathon Runners Eat?

In addition to training, nutrition is an important tool on the way to a successful marathon race.

Nutrition is a key element of athletic performance both during marathon training and during the marathon itself. By optimizing your diet, you can improve your performance by a few percent during training and on race day.

Many paths can lead to the goal

One widely discussed topic is carbohydrates. Especially during the training phase and in the last days before the marathon, there are different strategies that can lead to success depending on the individual. What they all have in common is that the carbohydrate stores at the start of the marathon must be as full as possible. But fat metabolism also plays an important role.

Here we explain what to pay attention to when eating and drinking during marathon training and during the marathon itself.

Nutrition during marathon training

Structured marathon training begins about 12 to 16 weeks before the marathon. This means that marathon training plans generally start 12 or 16 weeks before the race. During this time, we not only train specifically for the marathon but also adjust our nutrition to match the training.

A major risk!

Since marathon training is very demanding due to high training volumes, a balanced diet is an important component for achieving training goals. Marathon runners have a big advantage: because we burn a lot of calories while running, we rarely need to restrict our food intake. Counting calories is therefore of little importance for long-distance runners. Training could only become dangerous for runners who naturally eat very little or have a low appetite, as undernourishment could result in insufficient energy for upcoming training sessions.

What should we pay attention to during marathon training?

A permanent low-carb strategy rarely works for marathon runners. For long runs, we need carbohydrates, and also for recovery afterwards.

Our body primarily relies on carbohydrate stores as an energy source during endurance sports. If these stores are empty or sparsely filled, there is not enough energy for effective training.

It is especially recommended to consume complex (long-chain) carbohydrates, which store glycogen two-thirds in the muscles and one-third in the liver. Complex carbohydrates with a low glycemic index (GI) can be found in various whole grains, raw potatoes, corn, millet, fruits, and peas.

Nutrition in the last days before the marathon

In the last 3 - 4 days before the marathon, fully filling the carbohydrate stores is the highest priority. Your body will need the full glycogen reserves during the marathon. If the stores are not full, performance will drop earlier, or you will have to supply your body with additional carbohydrates earlier during the marathon, which can cause digestive issues.

Fluids: Not too little, but not too much!

Fluids should not be neglected. The risk of dehydration during a marathon is rather low. It is sufficient to drink as much as you normally do in the days before the marathon, or slightly more, because carbohydrates must be stored with water in the muscles and liver. This is about 3 liters per day.

Drinking too much right before or during the marathon should also be avoided. Drinking too much can lead to discomfort or digestive problems.

The last 24 hours before the marathon

No experiments. Avoid eating large or heavy meals that are hard to digest. Breakfast should be approximately three hours before the marathon and rich in carbohydrates, but not heavy foods like whole grains. Spices should also be avoided. Proven options include toast or muesli. Fatty foods should be avoided. Individual differences apply, so test your optimal "marathon breakfast" during preparatory races or training runs.

Instead of water, light fruit juices or electrolyte drinks with vitamins, carbohydrates, and minerals are recommended. One hour before the marathon, a few sips of fluid are allowed, but not too much. If hungry, a banana or an energy bar is acceptable up to 30 minutes before the start.

Tip: Enjoy breakfast and eat slowly. This helps prevent cravings shortly before or during the marathon.

Proper nutrition during the marathon

There are no universal rules for the marathon itself.

Generally, our energy reserves only last about 90 minutes. This is too short for a marathon, making the marathon much more complex than shorter distances such as 10 km.

Why we have insufficient energy for the marathon

Energy is provided to our body through adenosine triphosphate (ATP). When ATP is broken down, energy is released. ATP is produced by metabolizing nutrients, primarily carbohydrates and fats.

Not all carbohydrates are optimal

During the marathon, we need new energy in the form of carbohydrates. It is important to use carbohydrates that are quickly available to the body during the race.

High GI carbohydrates (glycemic index) cause a rapid rise in blood sugar. Energy is then available quickly. These products are especially recommended towards the end of the marathon, ideally combined with some fluids to avoid a sharp drop in blood sugar due to insulin release, which can lead to hypoglycemia and a sudden drop in performance.

The ideal ratio is 7 grams of sugar per 100 ml of fluid.

Why we need carbohydrates, not fats

Carbohydrates provide 4.1 kcal per gram, fats 9.1 kcal, but fat energy is released more slowly.

The body can store about 600 grams of carbohydrates, which equals approximately 2,400 kcal. This is generally not enough for a full marathon. Fat metabolism is slow, so energy is released slowly and is not optimal for marathon performance.

We therefore need plenty of carbohydrates and not extra fats during the marathon.

Energy gels provide fast energy; bananas less so

Energy gels are very efficient during races. Energy bars or bananas also provide carbohydrates, but bananas have a lower GI and take longer to provide energy. Therefore, bananas are less ideal towards the end of a race.

For drinking, water is recommended, as well as isotonic drinks or water with potassium and salt. Do not drink too much at individual stations; small sips more often are better.

For marathon running, it is recommended: 50 grams of carbohydrates per hour for recreational runners, 90 grams per hour for elite athletes. A 50-gram energy bar contains about 35 grams of carbohydrates, so one bar every 45 minutes is sufficient.

Nutrition after the marathon

Even if appetite is low, food and fluids must be consumed after the marathon. Immediately after, plenty of carbohydrates are needed to refill glycogen stores and speed up recovery, preferably complex carbohydrates.

Proteins are also important in the following days. Muscles are mainly composed of protein, and marathon running stresses muscle structures, so protein is necessary to rebuild damaged structures.

Optimal marathon nutrition: Key facts summarized

• During marathon training, regularly consume low GI carbohydrates
• In the last 3 - 4 days before the marathon, fully fill carbohydrate stores
• Lightly digestible meals on the evening before the marathon and for the final breakfast
• During the marathon, consume high GI carbohydrates, especially in the final phase
• After the marathon, consume low GI carbohydrates and proteins

High glycemic index foods: energy gel, maltose, glucose, honey, sweets, sugary fruit juices, french fries, cooked carrots, popcorn, instant rice, cola, bananas

Low glycemic index foods: whole grains, legumes, dairy products, vegetables, fruits, durum pasta, broccoli, raw carrots