Image Of An Athletic Woman Slicing Fruit While Preparing Smoothie In The Kitchen For Honing In On Her Marathon Nutrition

A Complete Guide to Proper Marathon Nutrition

BY Asker Jeukendrup

Training for your marathon means more than just putting in miles. Having your nutrition plan dialed in for before, during, and after the race is equally important. This guide from sports nutrition expert Asker Jeukendrup will help you create the right plan for all aspects of your race day nutrition.

Training and nutrition are the two of the most important factors determining performance on race day. Most runners spend many hours per week training, planning, and preparing their training sessions, but how much time is spent on nutrition? Often, nutrition is taken for granted and this could jeopardize all the hours and days of hard training.

Questions about what to eat before, during, and after the race are commonly asked by beginners and even advanced runners. Here is a quick guide to getting your nutrition for your marathon just right.

How Do I Fuel for a Marathon?

Interestingly, the story does not start the week before the race. Like training, it starts many weeks before the event!

  • Test a variety of food options in your training to determine which ones work best for you.
  • Understand what will be provided in aid stations.
  • Increase your carbohydrate intake moderately in the days before your race to fill up your glycogen stores.
  • Eat a familiar breakfast 3-4 hours before your start. Avoid excessive fiber, fat or protein.
  • Bring a gel or carbohydrate drink to sip the hour before your start.
  • Focus on hydration and carbohydrate intake during your race.

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Early Preparation

Preparation starts many weeks before the event. You need to know some of the basics of the race like: what nutrition will be provided on the course, where are the feed stations, and what are the weather conditions likely to be. You may not be able to influence the weather, but you can prepare for the conditions. Finding out what nutrition is going to be handed out is important too because it would be a good idea to practice with this nutrition and make sure you can tolerate it and you can adapt to it. If you can’t tolerate it, it is better to find out weeks in advance than on race day.

Creating Your Marathon Nutrition Plan

The first step is to figure out what nutrition works best for you. This includes not only products but timing as well. Start doing this 10 weeks before the event, pick your long-run training to practice and follow your plan, or build up to it. As mentioned above, first try using the products that will be available on the course. If those do not agree with you, start experimenting with other products.

Carbo-Loading Before a Marathon

In the days before the race, you should make sure your fuel stores (muscle glycogen) are full. In the old days, extreme carbo-loading regimes were followed with days of no carbohydrates, days of extreme carbohydrates, a depletion run a week before, etc. This practice is not necessary. Very high muscle glycogen levels can be achieved by just eating more carbohydrates.

Eating more carbohydrates does not mean overeating or eating as much as possible! It just means making sure more of your daily calories are coming from carbohydrates at the cost of some fat. It is a good idea to have the last large meal at lunchtime the day before and to have a lighter meal in the evening. This is also something you should practice in the weeks before or when you have a smaller race coming up. If you frequently suffer from gastrointestinal problems, reduce your fiber intake to a minimum the day before the race.

From a purely practical point of view, you also need to plan in advance, especially if you are traveling. Make a reservation at a place where you know the food is good. Don’t wait and make it up on the go and end up at fast food place or lining up for hours. Your legs need to work hard enough the next day.

Pre-Marathon Breakfast

Breakfast is important because it replenishes your liver glycogen. Carbohydrate is stored in the liver but during the night, the brain uses this carbohydrate, so when you wake up, there is not much left. Since this will delay the point at which you bonk, it is important to eat a carbohydrate-rich breakfast. Again if you suffer from gastrointestinal problems, reduce your fiber intake

Exactly what the breakfast should consist of depends on personal preferences. Some people run really well on a couple of bagels and a coffee, others prefer oatmeal, waffles with syrup, a couple of energy bars or a small bowl of rice. Whatever you choose, I would recommend that it has at least 100 grams of carbohydrates and that you use this breakfast at exactly the same timing before hard training and smaller races.

The best timing is probably 3 to 4 hours before the start. If you don’t suffer from gastrointestinal distress, 2 to 3 hours before might still work. Check your urine color. If it is pretty light, you are ok, if it is dark, keep drinking a little more. No need to go crazy on the fluids, but you don’t want to start with dark-colored urine.

The Hour Before the Start

The hour before is usually spent anxiously waiting. Make sure you bring a water bottle to sip and a gel to take in the 15 minutes before the race starts. Practice this several times in training. Whatever you consume in the minutes before the start will become available during the run because it takes a little time to absorb. I, therefore, usually calculate anything you take in this timeframe as part of your carbohydrate intake during the race.

What to Eat During a Marathon

During the race, two things will be important: carbohydrates and fluids. For both, it is important to take enough, but not too much. Too much fluid or carbohydrates can cause an upset stomach. Drinking large amounts of fluid that lead to weight gain is certainly not recommended and may even cause hyponatremia—a potentially health-threatening condition.


The only way to really understand your sweat rate and how much drinking is required is by weighing yourself before and after training in the weeks leading up to the marathon. This way, your sweat rate can be calculated by subtracting the weight after from the weight before and adding the volume of fluids consumed. There are various sweat calculators on the internet that will help you do these calculations.

If you are running in similar conditions and at a similar pace to the actual marathon, sweat rates will be similar. The cups you receive during a marathon usually contain about 150 ml (5 oz.) and you probably consume about 100 ml of that (3 oz.). To prevent dehydration, you will have to drink amounts that are similar to your sweat rate. A runner’s stomach can empty about 6 to 7 ounces (180 to 210 ml) of fluid every 15 minutes during running, representing about 24 to 28 ounces (720 to 840 ml) per hour. This, however, can be trained, practiced, and improved if needed.


Carbohydrate requirements are more straightforward. Studies suggest that you can use over 60 grams of carbohydrates per hour from most carbohydrate sources. Athletes should target 50 to 70 grams per hour. An athlete finishing in the 4 to 5-hour range will be OK with being at the lower end of this. Athletes aiming for a 3-hour finish could benefit more from being at the higher end of this range. Recent studies also suggest a dose-response relationship. In other words: more carbohydrates could be better for performance. But of course, too much might cause gastrointestinal problems and have the opposite effect. It becomes a balancing act with your “gut feeling” as your gauge.

Carbohydrate sources

  • 1 Banana 24-30 g
  • Gel   21-27 g
  • Energy bar 20-40 g
  • 4-5 Chews 16-25 g
  • 10 Jelly beans 11 g

The good news is that your gut is extremely trainable, and you could actually train it to tolerate these drinks, gels, bars, etc., which means you will have to use it in training regularly. So use all the products you will use in the race in training!

Also, avoid experimenting on race day with new products. There is also a flipside to this coin. Those athletes who are not regularly consuming carbohydrates, are trying to lose weight, are on a high-fat diet, and so on, will have a diminished capacity to absorb carbohydrates and are more likely to have gastrointestinal problems during exercise.

Electrolytes (sodium) may help with absorption, and some sodium in your drinks or gels is therefore recommended but don’t overdo it! A marathon is too short to cause extreme sodium losses that will impact performance or health.

Many athletes use caffeine before or during a marathon to boost their performance. This practice is indeed supported by scientific evidence, although there may be individual differences in tolerance and perception. It works for most but may cause negative effects for a few. Studies have demonstrated that relatively small amounts of caffeine are required to give optimal effects (3mg per kilogram body weight; 200mg for a 70kg person), and a general recommendation is not to exceed a daily intake of 400 mg caffeine from all sources. Caffeinated gels usually contain between 25 and 50mg of caffeine, and an espresso 80 to 100 mg.

What to Eat After a Marathon

Although there are guidelines to recover quickly after a marathon. Does it really matter that much? Most people won’t run another marathon the next day or race again for a couple of weeks. So enjoy your achievement and indulge in moderation!

A Helpful Checklist for Proper Marathon Nutrition

Weeks Before

  • Study the course, the nutrition on the course, and develop a plan.
  • Practice, practice, practice: Train with your race nutrition plan, train with the drinks on course, train with gels or whatever you will use.
  • Practice your breakfast plan and also the meal plan the night before. Find out what works best for you.
  • Make a reservation for dinner the night before at a place that you know is good. Don’t wait till the last moment.

Days Before

  • Buy your race nutrition, don’t wait till the last moment.
  • Increase your carbohydrate intake by eating more carbohydrate-rich (not just eating more).
  • Reduce fiber intake 1 to 2 days before the event if you often suffer from gastrointestinal problems.

Pre-Race Breakfast

  • Have your standard race breakfast that you have trained with 2.5-4 hours before.
  • Avoid high fiber, high fat and high protein foods.
  • Aim for at least 100 grams of carbohydrates.
  • Drink enough fluid and check that your urine color is light.

The Hour Before

  • Start your race fueling  5-15 min before the start (a gel with a few sips of water is an example).

During Your Marathon

  • Stick to your nutrition plan, but don’t stick to it at all costs.
  • Don’t experiment with anything new. Stick to what you have practiced.
  • Aim for 30-60 grams per hour.
  • Use sports drinks, gels, chews, and bars, depending on your personal preference. You can mix and match to achieve your carbohydrate goals.
  • Avoid high fiber fat and protein intake during the run.
  • Don’t overdrink, don’t under drink. Try to match our sweat loss or a little less. Some weight loss at the end (2% of your body weight is fine).
  • Don’t use excessive salt or electrolyte intake.


Cermak, N.M. & Van Loon, L.J.C. (2013, November). The use of carbohydrates during exercise as an ergogenic aid. Retrieved from

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About Asker Jeukendrup

Asker Jeukendrup PhD is a Professor associated with Loughborough University and director of MySportScience Ltd. After obtaining his degrees at Maastricht University in the Netherlands, he spent a year at the University of Texas at Austin before accepting a position at the University of Birmingham where he was the director of the Human Performance Laboratory. He was the Global Senior Director of the Gatorade Sports Science Institute, defining strategies for research, education and sport science services.’He has published over 200 papers and book chapters and has published 8 books. Asker has been a training and nutrition consultant to several elite athletes worldwide, including the Dutch Olympic teams, Chelsea FC, UK Athletics and some of the World’s best marathon runners (Haile Gebrselassie), swimmers, and triathletes (Chrissie Wellington, Andreas Raelert). Asker has completed 21 Ironman races including the Ironman world championships in Hawaii.

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