Marathon Nutrition: How to Fuel Your Next Race Like a Pro

Why do professional runners like Emily Sisson and Connor Mantz run marathons faster than you and I do? Is it because they’re genetic lottery winners who train more than 120 miles per week? No! It’s because they fuel their marathons and half marathons very differently than most runners.

Okay, it’s also because they’re genetic lottery winners who run more than 120 miles per week. But elite runners do in fact fuel their marathons differently than most runners, and science tells us they gain a significant performance advantage by doing so.

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We can’t change our genes, and you probably wouldn’t fare well on 120-plus miles of training every week (I know I wouldn’t!), but there’s nothing stopping you from lopping minutes off your finishing times by elevating your nutrition game. These three steps will set you up to fuel your next marathon like a pro:

Aim high

Arguably the most thoroughly proven fact in all of endurance sports science is that carbohydrate consumed during exercise boosts performance. If you’re not consuming carbs during races lasting longer than an hour or so, you’re leaving time on the table; it’s as simple as that. But how much carbohydrate is enough?

More than you think. Studies show that athletes perform better on 30 grams of carbs per hour than they do on zero, better still on 60 grams per hour, and best of all on 90-plus grams. Most elite runners today aim for this last number, which equates to roughly four standard gel packets per hour, but very few recreational marathoners come anywhere close to it.

Why not? A lot of runners tell me their current fueling habits seem to work just fine for them, not realizing how much better a pro-style fueling plan would work. In one study, runners who consumed 60 grams of carbs per hour completed a marathon nearly 11 minutes faster on average than fitness-matched runners who did their own thing nutritionally.

The second excuse I hear for not fueling like the pros in marathons is that taking in lots of carbs makes their tummy uncomfortable. Keep reading.

Train your gut

Blaming gels and sports drinks for in-race gastrointestinal issues such as bloating and nausea is understandable but a bit off the mark. According to a scientific review published in the International Journal of Environmental Research and Public Health in 2021, runners who consume more carbs in competition are not more likely to experience GI distress during races. But do you know who is? Runners who fail to practice high rates of carb intake in training!

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Other research has shown that the human gut can be trained to tolerate higher levels of carbohydrate intake on the run. The key is to go about the process systematically. Start by eating more carbs before you run. Try to consume at least 100 grams (or 400 calories) of carbohydrate between 2 and 3 hours before you start. If you run early in the morning and don’t have that kind of time, just do the best you can, wolfing down half a banana or a few spoonfuls of apple sauce before you head out the door. This will not only start the process of training your gut but will also give you a performance boost in its own right. A 2002 study by researchers at Loughborough University found that runners performed 10 percent better in an exhaustive treadmill run after a high-carb breakfast than they did on an empty stomach. If you think you’re “getting away with” not eating before runs . . . you’re not!

As for fueling during runs, set aside one run per week—preferably your longest run—to practice gut training. Start with an incremental increase relative to your current habits. So, for example, if you’re currently taking in one gel packet per hour, try one every 50 minutes. Keep going until you’re able to take in 90 grams per hour without significant GI issues (minor discomfort is acceptable).

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If you run into problems, don’t give up! Act as if you’ll lose your job if you aren’t able to reach that magical 90-gram threshold, which is exactly the situation the pros find themselves in. There are dozens of different products out there. Keep trying different options until you find one you can tolerate in larger amounts. And be willing to accept a two-steps-forward-one-step-back pattern of progress. If you try to consume 70 grams of carbs per hour one week and vomit, drop back down to 60 grams for a week or two and then try again at 70 grams.

Pack light

If you watch the lead group in a major marathon such as Boston or London, you’ll notice that the runners aren’t wearing fluid packs or belts or carrying bottles. That’s because fluid is heavy, and carrying it would partly negate the benefits of fueling properly. Yet non-elite runners do this all the time.

True, elite marathoners have their own bottles waiting for them on tables positioned at 5-km intervals. But I’ve run 50 marathons as an amateur and I never carried my own fluid, and you shouldn’t either! Just take cups from the aid station volunteers—that’s what they’re there for. Practice grabbing cups on the run, pinching the top to prevent spillage, and downing the contents in one big gulp between breaths. It’s not that hard.

So much for fluid. Carbs are another matter. You can get some carbs at aid stations if you choose the sports drink option over the water option, but not nearly enough to optimize performance. You’ll need to carry gel packets to supply the balance—as many as 16 of them if you’re a 4-hour marathoner aiming for 90 grams per hour—but the combined weight is minuscule compared to that of a full fluid bladder.

If you’re repulsed by the idea of slamming 16 gel packets, try this trick that I learned at some point in my 50 marathons: Purchase a couple of those little gel flasks made by Hammer Nutrition and others. Squeeze a few gel packets into each and mix in just enough water to turn the solution liquid (it takes surprisingly little). On race day, sip from the flasks at frequent intervals timed to deplete their contents just before you finish. This method is far more palatable than swallowing entire gel packets, and a 2020 study reported that consuming smaller amounts of gel more frequently results in better performance compared to a large single dose. True, the pros don’t practice this particular method, but they have the luxury of not needing to. And the reality is that you and I are not pros, so we can’t expect to do everything the same!