Get access to everything we publish when you sign up for Outside+.
Running a successful marathon is undoubtedly challenging. At 26.2 miles, there’s more opportunity for problems to undermine the outcome of the race.
And one area that sets the marathon apart from shorter races is fueling. The human body only stores enough carbohydrate in the muscles, blood, and liver (in the form of glycogen) for roughly 20 miles of running, especially at more strenuous intensities.
Run out of fuel and the inevitable crash or bonk happens. Any marathoner who has “hit the wall” around mile 20 of a marathon will attest to the pervasive fatigue and dead-leggedness that follows. Slowing down is physiologically necessary to conserve the rapidly diminishing fuel stores that power a marathon performance.
The solution? First, proper marathon training is essential to teach your body to conserve fuel and use it wisely. Next, a combination of carb-loading before and during the race will boost carbohydrate stores and available fuel to help you finish the marathon strong.
Follow these do’s and don’ts of marathon fueling to help your next marathon be your best.
Do carb-load before the race
Carb-loading works. In an interesting study published in the International Journal of Sports Medicine, researchers followed over 250 runners who competed at the London Marathon. They found that only 12 percent consumed enough carbohydrates before the race—and those that did ran an average of 13.4 percent faster!
The new guidelines suggest 7 to 10 grams of carbohydrates for every kilogram (2.2 pounds) of body weight. This is admittedly more carbohydrates than most runners are used to eating; 1 to 2 liters of sports drink is a helpful way to make eating all those carbs possible.
Take your pre-race fueling seriously. For a 4-hour marathoner, this could mean running more than 25 minutes faster than if you didn’t focus on carb-loading!
Don’t wing it
A runner once told me he was going to rely on adrenaline to get him over the finish line of his first marathon. But that’s a very bad idea!
First, adrenaline is not adequate fuel for an endurance event (it’s for short bursts of high intensity energy, typically in a “fight or flight” situation).
Not having a nutrition plan for race day is like going into an exam without studying. You simply will not be prepared.
Instead, use the tips in this article to put a plan together. And of course, practice it before the race.
Don’t do anything new on race day
This is a well-worn piece of advice for any runner, no matter the distance. Don’t wear new shoes, shorts, or have different foods for breakfast. And experimenting with new fuels or a different fueling schedule is introducing a potentially disagreeable GI situation!
Stick with foods that are compatible with your stomach both the day before and on race day.
Which leads us to my next point…
Do practice before race day
Just like you practice long runs, pacing, and racing strategy before your goal marathon, you should also practice your exact fueling strategy before the big day. There should never be any surprises when you’re racing.
Aim to run two to three long runs using the same fueling schedule you plan to use on race day. Make sure everything is planned: use the same fuel, at the same time of day, in the same timing pattern that you will on the day you race your marathon.
This helps ensure that there won’t be any surprises when you finally line up to race.
Do consume adequate carbs during the marathon
During the race (and when you’re practicing), it’s essential to eat the right amount of carbohydrates.
Too little and you risk limiting your potential. Too much, and you risk GI distress.
With proper carb-loading before the race, most runners then need about 45 to 60 grams of carbohydrate per hour during a marathon for optimal performance. This works out to be about two gels (or equivalent) per hour.
To supply a steady stream of fuel and to reduce the likelihood of a porta-potty break, break that into two sessions: one gel every 30 minutes during a marathon.
Also be sure to drink roughly 4 ounces of water with each gel. The electrolytes in the gels must be processed with water (and too many electrolytes, if you drink sports drink, can leech water from your cells for that processing, causing dehydration). One or two mouthfuls of water is all you need.
With these strategies, fueling for a marathon becomes simpler. And racing the marathon will be a lot more successful!