How Many Carbs Per Hour Do You Need for Running?

How many carbs per hour running needs depends on how long you’re out: none for runs under about 45 minutes, 30 to 60 g an hour for one to two and a half hours, and up to 90 g an hour beyond that. A gut-trained minority now pushes to 120 g, but that is a trained skill, not a starting point.

Those bands come from the joint ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position statement and from Asker Jeukendrup’s duration-based guidelines. The interesting part is why the ceilings sit where they do, and how to climb them without spending the last 10K of a Malaysian marathon looking for a toilet.

How many carbs per hour for each race length?

The amount rises with duration because the longer you run, the more your own glycogen runs down. Here are the bands from the 2016 joint position statement (Thomas et al., 2016) and Jeukendrup’s 2014 review, matched to races you’ll actually enter here.

Jeukendrup notes the numbers don’t scale with body weight or training status. A 55 kg runner and an 80 kg runner start from the same targets. He also says they may need to come down when exercise intensity is low, which matters for the walking-heavy middle of a trail ultra (Jeukendrup, 2014).

Why is 60 g per hour the first ceiling?

Because your gut absorbs glucose through a transporter that tops out around 60 g an hour. Jeukendrup’s review puts the oxidation limit for a single carbohydrate source at about 60 g an hour. Go above it with glucose-only products and the extra sugar sits in your intestine, which is a reliable recipe for bloating, cramping and the sprint to the portaloo.

Fructose uses a different transporter. Mixing glucose (or maltodextrin) with fructose lets you absorb more in total, which is why most gels aimed at long races now list both on the label. If you want to go past 60 g, check that your fuel contains two sugar types.

More is not always faster, either. In a study of 51 cyclists and triathletes across four labs, performance improved as carbohydrate rose from 0 towards 78 g an hour, then the gains flattened (Smith et al., 2013). That trial was a two-hour ride plus a time trial, so it fits a marathon better than an ultra, but the shape of the curve is the point: the jump from 0 to 60 g is worth far more than the jump from 80 to 100.

Is 120 g per hour worth it?

For most Malaysian age-group runners, not yet. The 120 g headlines come from elite athletes with trained guts.

In a Spanish trial, 20 elite male mountain runners who had already done nutrition and gut training took 60, 90 or 120 g an hour during a mountain marathon with about 4,000 m of cumulative slope. The 120 g group reported a lower internal load and showed lower markers of muscle damage the next day (Viribay et al., 2020). It did not measure finishing time as its main outcome.

A lab study with highly trained cyclists found 120 g an hour raised the amount of ingested carbohydrate burned compared with 90 g, but did not spare any more of the body’s own stores (Podlogar et al., 2022). The authors called for performance studies. So the honest summary is that 120 g is possible and probably helps some elites, and we don’t yet know how much it helps a 6-hour marathoner.

Our view: get comfortable at 60 g, then 90 g in long training runs. If you can hold 90 g through a hot four-hour run without your stomach complaining, you’re ahead of most of the field at any Malaysian ultra.

What do 60, 90 and 120 g look like in real food?

In practice, 60 g an hour is two typical gels or a gel plus a banana. Gels vary, so read the label: most give somewhere between 20 and 30 g each. A medium banana gives roughly 25 g. A 6% sports drink gives 30 g per 500 ml.

• 60 g an hour: one gel every 30 minutes, or a gel plus half a banana from the aid station.
• 90 g an hour: two gels plus 500 ml of 6% sports drink, or three gels with water.
• 120 g an hour: four gels, or a high-carb drink mix plus gels. Only after weeks of practice.

At most Malaysian road races you’ll find water, an isotonic drink and sometimes bananas. Don’t count on anything else, and don’t count on the isotonic drink being the same one you trained with. If you rely on a sports drink for half your carbs, check the brand the organiser has announced and work out its grams per cup.

How do you train your gut to take more?

You train it the same way you train your legs: by doing it regularly, at race effort, and building up. The best-known study is from Ricardo Costa’s group at Monash University. Runners did two weeks of repeated gut-challenge sessions, taking 30 g of carbohydrate every 20 minutes during exercise, which is 90 g an hour. Gastrointestinal symptoms dropped by about 60%, and performance in a one-hour distance test after a two-hour run improved by about 5% in the carbohydrate groups, with no improvement on placebo (Costa et al., 2017).

An earlier Australian Institute of Sport study found that 28 days of training with high carbohydrate availability increased how much ingested glucose cyclists could burn during exercise (Cox et al., 2010). The gut and the muscles both adapt.

A practical way to start:

1. Pick one long run a week. Take 40 to 60 g an hour from the first 30 minutes.
2. Each week, add about 10 g an hour if your stomach stayed quiet.
3. Use the exact gels, drinks and timing you’ll race with.
4. Do some of these runs in the heat of the day, not only at 5.30 am.

The last point matters more here than in most countries. Sports Dietitians Australia’s position statement on exercise in heat notes that heat stress can disturb gut function (McCubbin et al., 2020). A plan you tested on a cool evening at Bukit Jalil may not survive 10 am in Putrajaya.

What changes in Malaysian heat and humidity?

Heat makes the same carb target harder to stomach, so you need fluid with it and a little more patience. A few things we see go wrong on Malaysian courses:

Gels without water. A concentrated gel on a dry mouth is unpleasant and slow to leave the stomach. Time your gels just before a water station so you can wash them down.

Warm sports drink. A cup of isotonic drink that’s been in the sun since 4 am is still carbohydrate. Count it, even if it tastes like regret.

Skipping early fuel because you’re “not hungry yet”. In the heat, appetite fades as the morning warms up. Fuel from the first 30 to 45 minutes in races over two hours, while your stomach still cooperates.

For the sodium side of a hot race, see How Much Sodium Do Runners Need Per Hour?, and for a full race-day timeline, our KLSCM race nutrition plan.

How does fuelling change in an ultra?

In an ultra the hourly target stays similar, but the food gets more real and the plan matters more than the number. Over eight to 20 hours, gels alone get hard to face. Rice balls, potatoes, sandwiches and noodle soup at night checkpoints give you carbohydrate with texture and salt, and a break from sweetness.

Intensity is lower too. On long climbs where you’re power-hiking, you burn carbohydrate more slowly, and Jeukendrup suggests targets can come down a little when intensity is low. A sensible ultra plan for most runners is 60 to 90 g an hour, with more on runnable sections and less on long hikes.

Some ultra runners also want a little protein in the middle hours; we looked at that in Protein During Ultramarathons. If that’s you, our QC Stamina pouch lists 42.2 g of carbohydrate, 13 g of protein and 221 mg of sodium per 65 g serving, mixed with 150 to 200 ml of water, and is meant for the middle and later hours of long events. If you’re racing under about four hours, gels, sports drink and water will do the job.

For a training block that builds this in from week one, our 12-week plan for your first 50K trail ultra includes long runs where you can rehearse it.

References

1. Thomas DT, Erdman KA, Burke LM (2016). American College of Sports Medicine joint position statement: nutrition and athletic performance. Medicine & Science in Sports & Exercise, 48(3), 543-568. doi:10.1249/MSS.0000000000000852
2. Jeukendrup A (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), S25-S33. doi:10.1007/s40279-014-0148-z
3. Smith JW, Pascoe DD, Passe DH, et al. (2013). Curvilinear dose-response relationship of carbohydrate (0-120 g/h) and performance. Medicine & Science in Sports & Exercise, 45(2), 336-341. doi:10.1249/MSS.0b013e31827205d1
4. Viribay A, Arribalzaga S, Mielgo-Ayuso J, et al. (2020). Effects of 120 g/h of carbohydrates intake during a mountain marathon on exercise-induced muscle damage in elite runners. Nutrients, 12(5), 1367. doi:10.3390/nu12051367
5. Podlogar T, Bokal Š, Cirnski S, Wallis GA (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g/h versus 90 g/h. European Journal of Applied Physiology, 122(11), 2393-2401. doi:10.1007/s00421-022-05019-w
6. Costa RJS, Miall A, Khoo A, et al. (2017). Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism, 42(5), 547-557. doi:10.1139/apnm-2016-0453
7. Cox GR, Clark SA, Cox AJ, et al. (2010). Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology, 109(1), 126-134. doi:10.1152/japplphysiol.00950.2009
8. McCubbin AJ, Allanson BA, Caldwell Odgers JN, et al. (2020). Sports Dietitians Australia position statement: nutrition for exercise in hot environments. International Journal of Sport Nutrition and Exercise Metabolism, 30(1), 83-98. doi:10.1123/ijsnem.2019-0300