The days leading into a marathon can be stressful. Runners have worked hard and are eager to turn their weeks of hard work into a personal best. Gastrointestinal distress is one of the biggest causes of marathon misfortune, but thankfully the IAAF and International Journal of Sport Nutrition and Exercise Metabolism have partnered and released open-access studies on the best way to fuel your upcoming 42.2K.
48 hours before race time
In the day or two before your big race, you’ll want to increase your carbohydrate load. Consider high-carb and low-fiber meals to reduce the likelihood of a mid-race bathroom issue.
The equation to determine how many carbs you should be eating ahead of your marathon is 10-12 grams of carbs per kilogram per day. So for a 135 pound person that’s roughly 720 grams of carbohydrate per day, starting about two days out. An average bagel has 50 grams of carbohydrates, so you could consume up to 14 bagels in one day. It’s recommended to diversify your intake, but the point is that you can take in a lot of carbs ahead of race time.
The morning of (4 hours before race time)
Eat your normal breakfast around four hours ahead of the gun. Remember, the rule of thumb is nothing new on race day so stick to what’s worked for you on big workout or long run days.
Two hours out
If your stomach can tolerate it, a snack 60-90 minutes ahead of go time is recommended, this is in addition to your pre-race meal. An easily digestible bar and a few sips of sports drink should do the trick–just a few carbohydrates before the gun goes. Caffeine (if you’re used to it) is also recommended in the 90 minutes before the start.
Aim for between 30 and 60 grams of carbohydrates every hour of your marathon. This can be a combination of a gel (which usually contains roughly 15 grams of carbs per pack) with a sports drink or chew. The amount of carbohydrates necessary is individual to every person but should be experimented with ahead of race day as an integral part of your training plan.