Marathon Fueling: What to eat during your Marathon with Coach Brian Comer

What is marathon fueling and what should you eat during your marathon? In sports and life, nutrition bears special importance for maximizing performance and healthy living. While good nutrition should be made a habit, there is particular emphasis that surrounds athletic competitions. The nutrition needs of the endurance athlete are unique and this is only emphasized more as race distances increase. 

As you get towards the marathon and beyond, you’re less likely to be able to get away with simply a pre and post run nutrition plan. That’s where fueling on the run comes into play. While not everyone is blessed with an “iron gut”, like shoes or other running gear, it often comes down to personal preference and what works for you individually. This article will seek to focus on marathon fueling, not so much for marathon training, but the pre-race, intra-race, and post-race considerations for marathon fueling as another spring marathon season looms on the near horizon.

Pre-Race Nutrition

Now when we say pre-race nutrition, while by default that would include nutrition during training, the purpose of the article is to look at the more immediate nutrition for the runner soon to embark on a marathon race. Nutrition is meant to nourish you and balance is key. 

While I used to be an advocate for the night before the race carbo load, I’ve since adopted the strategy of carbo loading 48 hours before a race then leaning more towards lean protein the night before. I feel less lethargic and full on the start line this way than when I carbo loaded the night prior. The night before protein rebuilds muscles, while 48 hours out I still get the carb benefits for race day. But as I mentioned, everyone has their own system, needs and preferences along with what they can physically tolerate. 

Much like new gear, you don’t want to be trying something new on race day, just stick to what you know. It’s important to pay close attention to what time your race starts, not just from a practice standpoint in training, but to allow yourself enough time in the morning to get up, eat, and digest. You’ll also want to make sure you’re hydrating and consuming carbohydrates as the body’s quickest and main source of energy. As alluded to, this can be overdone so be careful but the general recommendation is a maximum of 1 gram of carbohydrate per kilogram in body weight times the number of hours before exercise.  

Before the race is a good time to practice race day nutrition strategies when you’re out crushing your long run. Here’s where you can find out if you can stomach energy gels or chews or if you’re more of a sports drink kind of person. Most traditional sports drinks tend to be loaded with sugar so if you have the time and ability, you can try making your own. I’ve found that the Endurance Fuel powder from Tailwind Nutrition works wonders, as advertised, no gut bombs. They also have recovery powder as well but that’s more relevant for the post-run and post-race nutrition. As far as energy chews, some come packed with a little extra caffeine than others, both cross brand and within the same brand as well. It’s important to pay attention because while some like the extra kick of the caffeine, others may be more sensitive to caffeine and can have stomach problems because of too much caffeine intake. With gels, you can generally take one at the start of the race and then again every 30-45 minutes during the race. You can adopt the same timeline for sports drinks or even consume a little more often, as often as every 15 minutes if keeping to no more than 4-8 ounces.

Intra-Race Nutrition

Fueling strategies have also evolved and developed over time as more products make their way to shelves and give runners more options than ever before. While the go-to strategy originally was fast acting carbohydrates, it has since morphed into an emphasis of slow acting carbohydrates or a combination of fast and slow acting. The fast-acting carbohydrate strategy made sense at the time.  Your blood glucose falls naturally after 2-4 hours and given that you’re running at least that long if not longer during a marathon, quick fuel makes sense given the natural decrease within that time frame. 

By intaking chews, gels and sports drinks during the race, you’re also bringing some blood back to your GI tract.  The fact that your blood moves from your GI tract to your working muscles while you run is often why your GI tract may be extra sensitive. 

Slow acting carbohydrates are a little more generous to your gut as blood glucose levels are maintained a little more steadily compared to the spikes of fast acting carbohydrates. Factor in that your brain triggers insulin to ensure your blood glucose doesn’t get too high and you have all hands on deck as you make your way towards the marathon finish line. The combo strategy of fast and slow acting carbs for marathon fueling brings the best of both worlds. For most of the race, you use the slow acting strategy then add fast acting carbohydrates in the last 30-45 minutes of the race. You have steady energy for the bulk of the race and avoid the GI issues found with the fast-acting carbohydrates but then get the big energy burst in the homestretch. 

To review a comparison of popular gels on the market, check out this article: Comparing Popular Running Gels

So many options!

Post-Race Nutrition

While often a little harder to get down, especially immediately following the race, protein is the top source for rebuilding muscles after being torn down and put through the ringer. Consuming protein right after a run helps with the recovery process. That’s when you could consider finding more palatable options like the Tailwind recovery powder or a shake. Not everyone can stomach them though and if presented with whole food options, always opt for that over supplements. Even then, many runners have a hard time getting anything down immediately following a run and need some time for things to settle. Besides, if you’ve just been consuming gels and chews for the past 4 hours or so, the last thing you’d probably be feeling like is a shake.  This may not be practical or worth it immediately following the race but you want to make sure you at least get something into your system within that anabolic window that lasts for about 30 minutes after finishing. This often looks like a banana with some peanut butter, which is a good protein source. Chocolate milk has long been a go-to for many but if the lactose puts you off or is something you physically can’t do, there are various milk alternatives in addition to sports drinks to top off your electrolyte stores. The key here is to not wait too long before fueling post-race. Like all the other categories, everyone has their own preferences, it is just a matter of finding what works best for you. 


To reiterate, just like how there is no one-size-fits-all marathon training program, there is no cookie cutter one-size-fits-all marathon fueling strategy either. Through experimentation in training, you can find the fuels and strategies that work best for you while keeping in mind the general principles for good nutrition and more specifically, good marathon nutrition. With the sheer number of products available to runners looking for a marathon fuel source, it can be almost overwhelming but on the bright side, it leads to a surplus of options as you determine what keeps you running and what gets you across that finish line.

brian comer running coach

Brian Comer is a coach with Team RunRun. To learn more about him or to work with him, check out his coach profile.