How many carbs per hour should I eat in a marathon?

What do the guidelines say?

The 2016 joint position statement from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine sets up to 90 g of carbohydrate an hour for exercise lasting more than 2.5 to 3 hours.

Two reviews split it by how long you'll be out there. Burke et al. 2011 call 30 to 60 g/h a fitting target for longer events, and up to 90 g/h for events over 2.5 hours, from blends of different carbs. Jeukendrup 2014 recommends up to about 60 g/h from a single carb source for 2 to 3 hours of exercise, and about 90 g/h for longer efforts, which has to come from mixed sugars such as glucose plus fructose. Jeukendrup wrote it while at the Gatorade Sports Science Institute (PepsiCo), which sells sports drinks.

So your target depends on your finish time, not the distance.

Your finish time sets your carb target

Guideline carbs per hour during the race, by how long you will be out there

Seville average: 35 g/h

2 to 3 hours30 to 60 g/h · one sugar is fine

Over 2.5 to 3 hoursup to 90 g/h · mixed sugars

0306090

Your finish time sets your carb target

Race length	Guideline
2 to 3 hours	30 to 60 g/h
Over 2.5 to 3 hours	up to 90 g/h

How much do marathoners actually eat?

Much less. Jiménez-Alfageme et al. 2025 surveyed 160 runners at the 2022 Seville Marathon. They averaged 35 g of carbs an hour. 41.3% took under 30 g/h, and only 9.0% landed in the 60 to 90 g/h range. Under-fueling grew with finish time: 22.2% of runners under 3 hours took less than 30 g/h, rising to 42.1% at 3 to 4 hours and 66.7% over 4 hours.

Most marathoners under-fuel, and slower runners most

Share of 2022 Seville Marathon runners taking under 30 g of carbs an hour, by finish time

35 g/haverage intake

9%in the 60 to 90 g/h range

Under 3 h

22.2%

3 to 4 h

42.1%

Over 4 h

66.7%

0%25%50%75%100%

Share of 2022 Seville Marathon runners taking under 30 g of carbs an hour, by finish time

Finish time	Under 30 g/h
Under 3 h	22.2%
3 to 4 h	42.1%
Over 4 h	66.7%

It's a survey of self-reported intake, mostly from men, and carbs stopped predicting finish time once sex was accounted for. It shows what runners do, not what works.

Does fueling help you avoid the wall?

Hitting the wall is common. Smyth 2021 analyzed more than 4 million marathon results and found that 28% of men and 17% of women slowed by at least 25% for 5 km or more late in the race. On average it started at 29.6 km for men and 29.3 km for women, and cost about 31.5 and 33.2 minutes against a recent best. This is observational race data: it shows how often the wall happens, not that fueling alone prevents it.

A computer model of marathon fuel use (Rapoport 2010) adds that where you run out depends on your pace and your carb stores, and mid-race carbs can push it back. It's a model, not measured runners.

Do more carbs protect your late-race pace?

In the lab, for trained athletes, yes. In Norte et al. 2026, 16 trained cyclists and triathletes rode for 3 hours, then did a short all-out test. Their critical power was 277 W fresh. After the ride it fell to 236 W with water, 257 W with 60 g/h and 266 W with 120 g/h. Mazza et al. 2026 found the same pattern in 15 trained men: after 4 hours of riding, 15-minute time trial power fell 9.3% at 60 g/h and 6.4% at 100 g/h.

More carbs, more power left late

Critical power after 3 hours of moderate cycling, by carbs taken during the ride

No carbs60 g/h120 g/h

Fresh: 277 W

Waterno carbs

236 W

60 g/h

257 W

120 g/h

266 W

0100200300

Critical power after 3 hours of moderate cycling, by carbs taken during the ride

During the ride	Critical power after 3 h
Water	236 W
60 g/h	257 W
120 g/h	266 W
Fresh	277 W

Both are small lab studies of cyclists, almost all men, and neither measured race time. They suggest fueling protects late-race power.

Can you train your gut to take more?

Yes, and fairly quickly. In Costa et al. 2017, 25 runners practiced taking carbs on runs for 2 weeks. Gut symptoms fell 60% in the gel group and 63% in the food group, and distance in a 1-hour running test rose 5.2% and 4.3%, while the placebo group's fell 2.1%. In Miall et al. 2018, 18 runners took 90 g/h on daily 1-hour runs for 2 weeks: gut symptoms and malabsorption dropped, and running distance rose from 11.7 to 12.3 km.

Two weeks of gut training paid off

Change in distance on a 1-hour running test after 2 weeks of practice

Gut trainingPlacebo

Carb gelssymptoms down 60%

+5.2%

Carb foodsymptoms down 63%

+4.3%

Placebo

-2.1%

-4%0%+4%+8%

Change in distance on a 1-hour running test after 2 weeks of practice

Group	Distance change
Carb gels	+5.2%
Carb food	+4.3%
Placebo	-2.1%

Both are small trials from the same lab, but they agree: your gut adapts to the fueling you practice.

What it means for your race

Marathon. Start from your expected finish time. Around 2 to 3 hours, the guideline is about 60 g/h. Longer than about 2.5 to 3 hours, work toward up to 90 g/h if your gut handles it. Either way, most runners have room to take more than they do now.

Ultra. Guidance for long efforts sits around 90 g/h from mixed sugars. Ultras add heat, terrain and many hours of eating, so they get their own article.

Triathlon. A 70.3 or full distance lasts well past 2.5 hours for almost everyone, so the up to 90 g/h guidance applies. A review of 70.3 studies, von Känel-Cordoba et al. 2026, linked conservative bike pacing that spares glycogen to a better final run. That's an observed link, not proof.

When to start. Gut training has its own window: start about 12 weeks out, reach your race-level carbs by 4 to 6 weeks out, then use your race fueling in every long session after that. See your own timeline: try the demo.

Our take

This is our opinion, not a study finding. Pick your target from your finish time, not from what a pro takes. Write it down in grams per hour, practice it in every long run from about 12 weeks out, and raise it in small steps only when your stomach stays quiet. For most age-group marathoners, 90 g/h is a ceiling, not a starting point: the studies of 120 g/h used trained or elite athletes, and no study has tested it in recreational runners yet.

See where you stand for your race. Try the demo