Ultra Marathon Nutrition: A Practical Guide, 50K to 100K

Ultra marathon nutrition for a 50K to 100K comes down to eating steadily from the first hour: roughly 150 to 400 kcal an hour, most of it carbohydrate, with fluid matched to your sweat rate and sodium matched to that fluid. The runners who finish are usually not the ones with the cleverest plan; they are the ones who kept eating when their stomach and the heat told them to stop.

This page is our map for race nutrition on trails and ultras in Malaysia. Each section gives the short answer and points to the guide that goes deeper. If you want numbers for your own race straight away, put your duration and hourly targets into the race fueling calculator.

Start here: the race nutrition guides on this site

Why does an ultra need a different plan from a marathon?

Because the problem changes from running out of glycogen to running out of appetite. In a marathon you can carry nearly everything you need and the race is over before your gut gives up. In a 12-hour trail race you will burn several thousand kilocalories more than you can eat, the pace drops to a walk on the climbs, the sun moves overhead, and the food that looked fine at the start line becomes hard to swallow by the afternoon.

The International Society of Sports Nutrition’s position stand on single-stage ultras is the most complete summary of the evidence. It accepts that runners will finish in a calorie deficit, and frames the job as shrinking that deficit: 150 to 400 kcal an hour during racing, from 30 to 50 g of carbohydrate and 5 to 10 g of protein an hour, using a variety of calorie-dense foods (Tiller et al., 2019). The same paper points out that palatability, individual tolerance and a growing preference for savoury food in longer races all matter as much as the numbers.

That 30 to 50 g figure looks low next to the 60 to 90 g an hour often quoted for marathons. The two do not really disagree. The higher numbers come from lab and road studies at steady, fairly high intensity, and a review of ultra nutrition by Ricardo Costa and colleagues notes that whether those rates are tolerable in ultra competition is questionable, for both practical and gut reasons (Costa et al., 2019). Treat 30 to 50 g as a floor most runners can reach and 60 to 90 g as a ceiling you train towards. We explain the carbohydrate side in full in How Many Carbs Per Hour Do You Need for Running?

Does eating more actually help you finish?

The evidence we have says yes, though it is not tidy. At the Western States 100-mile race in California, researchers analysed the race diets of 16 runners. The six who finished took in calories at almost twice the rate of the ten who dropped: 4.6 against 2.5 kcal per kg per hour, with carbohydrate at 0.98 against 0.56 g per kg per hour. Finishers also ate more in the first 48 km (Stuempfle et al., 2011).

For a 60 kg runner, the finishers’ rate works out to about 59 g of carbohydrate an hour; the non-finishers’ to about 34 g. That is a small study, and the authors are careful to say that intake ranges were wide and other factors played a part. A runner who is struggling for other reasons will also stop eating, so the arrow points both ways. But it fits what most experienced ultra runners will tell you over teh tarik after a DNF: the trouble started hours before they stopped, when they skipped a feed because they did not feel like it.

The early hours are the cheapest time to eat. Your stomach is still calm, the morning is cooler, and you are moving fast enough on runnable trail that the calories are needed. Do not save your appetite for later. Later is when it disappears.

Why does your stomach fail in an ultra?

Because long running, heat and food are a hard combination for the gut, and almost everyone gets some symptoms. In a post-race survey of 272 Western States runners, 96% reported gastrointestinal symptoms at some point. Nausea was the one that mattered most: among finishers who said gut problems hurt their race, 86% named nausea, and among runners who dropped out because of their gut, 91% named it. Nausea peaked during the hottest and hardest part of the course (Stuempfle and Hoffman, 2015).

Heat is the part Malaysians should underline. A trail ultra here often starts in the dark at 4 or 5 am and runs straight into a humid late morning, which is exactly when that study found nausea at its worst. A follow-up study at a 161 km race linked nausea to endotoxaemia, a sign of a stressed and leaky gut, rather than to dehydration, core temperature or what runners ate (Stuempfle et al., 2016). In plain terms: the gut is suffering from the effort and the heat itself, and the cure is less about finding a magic food than about pacing, cooling and training the gut to cope.

Practical things that help on race day:

• Slow down when nausea starts. Walking for ten minutes, sipping water and pouring some over your head often settles it faster than forcing food.
• Switch texture. When gels stop going down, soup, rice, crackers or a liquid feed may still work.
• Eat small and often rather than big and occasionally. Half a gel every 20 minutes sits better than a full one every 40.
• Keep sipping fluid with food. A concentrated gel on a dry mouth is slow to leave the stomach.

Can you train your gut?

Yes, and it is one of the best-supported things you can do. In a randomised trial at Monash University, endurance runners spent two weeks doing daily one-hour runs while taking 90 g of carbohydrate an hour, or a placebo. On the carbohydrate programme, gut discomfort, total, upper and lower gut symptoms and nausea all fell during a later gut-challenge run, carbohydrate malabsorption dropped, and they covered more distance in the final one-hour effort. The placebo group did not improve (Miall et al., 2018). The ISSN position stand lists progressive gut training among its recommendations for ultra racing (Tiller et al., 2019).

For an ultra, gut training has two extra layers that road runners can skip. Train with the actual foods you will meet at aid stations, not just your favourite gel. And train some of it in the heat of the day: a plan that works at 6 am on the Bukit Kiara trails can fall apart at 11 am on an exposed ridge. The ultra plan in our 12-week training plan for your first 50K gives you the long runs to practise on.

What should you eat in the days before?

For a race of several hours, eat a high-carbohydrate diet for a day or two before, then a familiar, easy breakfast. The joint ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position statement recommends carbohydrate loading at 10 to 12 g per kg of body weight per day for 36 to 48 hours before events longer than 90 minutes, and 1 to 4 g per kg in the one to four hours before starting (Thomas et al., 2016).

For a 65 kg runner, 10 g per kg is 650 g of carbohydrate a day. That is a lot of rice, more than most people manage without trying, so lean on low-fibre, low-fat sources: white rice, noodles, bread, kaya toast, bananas, juice. Nasi lemak with extra sambal and fried chicken is a fine Malaysian dinner, but the coconut and oil add bulk without adding much carbohydrate, and it is not what you want the night before a 4 am flag-off.

The breakfast rule has to bend to the clock. If your race starts at 5 am, eating 1 to 4 g per kg four hours before means sitting down to breakfast at 1 am. Most runners do better with a solid carbohydrate dinner, a modest breakfast of 1 to 2 g per kg about 90 minutes to two hours before the start, and then feeding from early in the race.

How much should you eat per hour, and of what?

Start with 150 to 400 kcal and 30 to 50 g of carbohydrate an hour, then train upwards if your gut allows. Here is how that looks in practice, using food you can actually find or carry in Malaysia:

The ISSN stand’s point about savoury food is worth taking literally. After six or seven hours of sweet gels, many runners cannot face another one, and a salty potato or a cup of Milo at a checkpoint is suddenly the best thing they have ever tasted. Build both into the plan from the start, and alternate before you get sick of either.

Protein is a smaller question than it sounds. The ISSN stand suggests 5 to 10 g an hour during ultras (Tiller et al., 2019), mostly for practical reasons over many hours. Our guide to protein during ultramarathons weighs it up. For runners who want carbohydrate and protein in one drink at a drop bag, our QC Stamina pouch lists 42.2 g of carbohydrate, 13 g of protein and 221 mg of sodium per serving, mixed with 150 to 200 ml of water; the label suggests one every two to three hours in long events. If your race is under about four hours, gels, sports drink and water are simpler.

How much fluid and sodium in an ultra?

Drink to thirst within a ceiling set by your sweat rate, and plan sodium against the fluid you actually drink. The ISSN stand suggests 450 to 750 ml an hour during racing, about 150 to 250 ml every 20 minutes, rising in hot and humid conditions, and notes that ultra runners may need sodium at concentrations above most commercial drinks, more than 575 mg per litre, to reduce the risk of hyponatraemia (Tiller et al., 2019). Costa’s review adds that ultra runners can end up either underhydrated or overhydrated depending on duration and conditions, and that drinking to thirst generally keeps them in between (Costa et al., 2019).

The catch in Malaysia is that sweat rates here can easily outrun 750 ml an hour on exposed sections, then drop sharply at night or in the rain. Measure yours with the sweat rate calculator before you set a number. The full picture on fluid, sodium and overdrinking is in our hub page, Running Electrolytes and Hydration in Malaysia, and the hourly sodium numbers are in How Much Sodium Do Runners Need Per Hour?

One rule is worth repeating here because ultras are where it bites. If you weigh yourself at a drop bag and you are heavier than at the start, you are drinking too much, and more salt will not fix it. Large field studies at 161 km races found exercise-associated hyponatraemia in about one in seven finishers tested, and found that sodium supplements did not protect the runners who developed it (Hoffman et al., 2013; Hoffman and Stuempfle, 2015).

What changes when the race runs through the night?

Appetite, temperature and alertness all drop, and your plan has to account for each. Night sections in the hills, from Fraser’s Hill to the Crocker Range in Sabah, can be cool enough that your sweat rate halves. Drinking at your daytime rate then pushes you towards overdrinking, so cut back and let thirst lead.

Eating at night takes discipline because nothing feels urgent. Set a timer on your watch for every 30 or 40 minutes and eat something each time it goes off, even if it is only half a gel or a few crackers. Warm food at night checkpoints is worth sitting down for; a cup of soup or porridge gives you carbohydrate, fluid and salt at once.

Caffeine earns its place in the small hours. The ISSN ultra stand supports strategic use of caffeine to sustain performance late in races, particularly when sleep deprivation may compromise safety (Tiller et al., 2019). The ISSN caffeine position stand puts the effective range at 3 to 6 mg per kg of body weight, notes that doses as low as 2 mg per kg may work, and says very high doses around 9 mg per kg bring more side effects without extra benefit (Guest et al., 2021). For a 65 kg runner, 3 mg per kg is about 200 mg, roughly two cups of kopi. Most ultra runners split it into smaller doses through the night rather than taking it in one go, and hold it back until they need it.

What do 50K and 100K plans look like?

Here are two sketches for a 65 kg runner. They are starting points to test in training, not prescriptions. Plug your own numbers into the race fueling calculator to see the totals.

A 50K trail race, about 8 hours

Think of a hilly 50K on the trails of Hulu Langat or Janda Baik, starting at 6 am, with aid stations every 8 to 12 km.

• Night before: a big carbohydrate dinner, salted normally. Rice, noodles or bread with something you know your stomach likes.
• Breakfast, about 4.30 am: 80 to 130 g of carbohydrate, such as two slices of bread with kaya, a banana and a sweet drink.
• Hours 1 to 4: 40 to 60 g an hour, mostly gels and sports drink while the trail is runnable and the air is cooler.
• Hours 4 to 8: 30 to 50 g an hour, switching to bananas, potatoes and rice at aid stations as it gets hot and the gels lose their appeal.
• Totals: roughly 280 to 440 g of carbohydrate over the race, with fluid and sodium sized from a sweat test done in similar heat.

A 100K trail race, 18 to 22 hours

Think of the 100 km at the Borneo Ultra Trail Marathon in Sabah, or any 100K that runs through a full day and a night.

• Two days before: carbohydrate loading at 8 to 10 g per kg if you can manage it, about 520 to 650 g a day.
• Hours 1 to 6: 50 to 60 g an hour while you can still run and your stomach is fresh. This is where finishers in the Western States data pulled ahead.
• Hours 6 to 14: 30 to 50 g an hour, mixing sweet and savoury. Use drop bags for real food and a liquid feed you have tested.
• Night hours: a timer every 30 to 40 minutes, warm food at checkpoints, caffeine in small doses from midnight onwards, fluid cut back as the air cools.
• Last hours: whatever goes down. Sweet drinks, soup, the last gel in your pack. Something beats nothing.

On a 100K the drop bags do a lot of the work, so plan them with the same care as the race itself. Our ultra drop bag checklist covers what to pack and where.

How should you plan around aid stations?

Plan by time between stations, not by kilometres. A 10 km gap on a flat estate road might take an hour; the same distance over a ridge with 900 m of climbing can take three. The ISSN stand notes that ultra runners face multiple barriers to eating, and the gaps between aid stations are one of the most predictable (Tiller et al., 2019).

• Read the race manual for the aid station list and what each one serves. Many Malaysian trail races serve water and isotonic drink at every point, with fruit, biscuits and hot food only at the larger ones. Check, do not assume.
• Carry enough food for the slowest likely split between stations, plus one spare feed.
• Know what you will do at each station before you arrive: refill, eat, leave. A five-minute stop at each of eight stations is 40 minutes.
• In the heat, fill one bottle with plain water so you can pour it over your head without wasting your sports drink.

The 20 tips for hot, humid trail ultras in Malaysia go further into cooling and kit.

What about recovery after the race?

Start eating soon, and do not worry about precision. The joint position statement suggests 1.0 to 1.2 g of carbohydrate per kg an hour for the first four hours when rapid refuelling matters (Thomas et al., 2016), but after an ultra most runners are not racing again for weeks, so the priority is simply to get food and fluid in and let the gut settle. Rice, noodles, a sweet drink and something salty will do. Our guide to recovery after a marathon or ultra covers the days that follow.

Where should you start?

Pick your race, then work backwards. Measure your sweat rate in conditions like race day. Set your hourly carbohydrate, fluid and sodium in the race fueling calculator. Rehearse the plan on at least three long runs, one of them through the hot part of the day, with the foods you will meet on course. Then expect to change it on the day, because the plan that survives contact with a Malaysian ridge at noon is rarely the one you wrote at your desk.

References

1. Tiller NB, Roberts JD, Beasley L, et al. (2019). International Society of Sports Nutrition position stand: nutritional considerations for single-stage ultra-marathon training and racing. Journal of the International Society of Sports Nutrition, 16(1), 50. doi:10.1186/s12970-019-0312-9
2. Costa RJS, Knechtle B, Tarnopolsky M, Hoffman MD (2019). Nutrition for ultramarathon running: trail, track, and road. International Journal of Sport Nutrition and Exercise Metabolism, 29(2), 130-140. doi:10.1123/ijsnem.2018-0255
3. Stuempfle KJ, Hoffman MD, Weschler LB, Rogers IR, Hew-Butler T (2011). Race diet of finishers and non-finishers in a 100 mile (161 km) mountain footrace. Journal of the American College of Nutrition, 30(6), 529-535. doi:10.1080/07315724.2011.10719999
4. Stuempfle KJ, Hoffman MD (2015). Gastrointestinal distress is common during a 161-km ultramarathon. Journal of Sports Sciences, 33(17), 1814-1821. doi:10.1080/02640414.2015.1012104
5. Stuempfle KJ, Valentino T, Hew-Butler T, Hecht FM, Hoffman MD (2016). Nausea is associated with endotoxemia during a 161-km ultramarathon. Journal of Sports Sciences, 34(17), 1662-1668. doi:10.1080/02640414.2015.1130238
6. Miall A, Khoo A, Rauch C, et al. (2018). Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption. Scandinavian Journal of Medicine & Science in Sports, 28(2), 630-640. doi:10.1111/sms.12912
7. 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
8. Guest NS, VanDusseldorp TA, Nelson MT, et al. (2021). International Society of Sports Nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition, 18(1), 1. doi:10.1186/s12970-020-00383-4
9. Hoffman MD, Hew-Butler T, Stuempfle KJ (2013). Exercise-associated hyponatremia and hydration status in 161-km ultramarathoners. Medicine & Science in Sports & Exercise, 45(4), 784-791. doi:10.1249/MSS.0b013e31827985a8
10. Hoffman MD, Stuempfle KJ (2015). Sodium supplementation and exercise-associated hyponatremia during prolonged exercise. Medicine & Science in Sports & Exercise, 47(9), 1781-1787. doi:10.1249/MSS.0000000000000599