A Complete Guide to Proper Marathon Nutrition | TrainingPeaks

by Daniela Haynes | Sep 29, 2022 | Nutrition & Healthy Recipes

How do I fuel for a Marathon?

Nutrition continues to be a much discussed topic amongst marathon runners. 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.

Interestingly, the story does not start in the week before the race, like training it starts many weeks before the event! After a race it also seems to be one of the main topics, especially for runners who did not achieve their goals or had problems along the way.

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.

The 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 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.

Train Your Race 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

In the 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 carbohydrate, days of extreme carbohydrate, 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 carbohydrate does not mean overeating or eating as much as possible! It just means making sure more of your daily calories are coming from carbohydrate at the cost of some fat. It is a good idea to have the last large meal at lunch time 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 gastro-intestinal 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 travelling. 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-Race Breakfast

The 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 gastro-intestinal 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, other prefer oatmeal, waffles with syrup, a couple of energy bars or a small bowl or rice. Whatever you select, I would recommend that it has at least 100 grams of carbohydrate and that you use this breakfast with 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.

During the Race

During the race two things will be important: carbohydrate and fluids. For both it is important to take enough, but not too much. Too much fluid or carbohydrate 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 calculator on the internet that will help you do these calculations.

If you are running in similar condition 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 seem to suggest that you can use about 60 grams of carbohydrate per hour from most carbohydrate sources. Athletes should target 30 to 60 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 carbohydrate 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

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 carbohydrate, are trying to lose weight, are on a high fat diet and so on, will have a diminished capacity to absorb carbohydrate and 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.

After the 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

Weeks Before

Days Before

Pre-Race Breakfast

The Hour Before

During Your Marathon