Borneo Ultra Trail Marathon 2027 Fuel Plan for Kiulu’s Heat
For the Borneo Ultra Trail Marathon on 3 April 2027, carry enough water and food to cover gaps of about 10 km between aid stations, which on Kiulu’s climbs can mean two hours or more. Most runners will do well on 40 to 70 g of carbohydrate and 450 to 750 ml of fluid an hour, with planned sodium for anything past 90 minutes in this heat.
BUTM is not a high-altitude race. The Kiulu valley sits low, north of Kota Kinabalu, and Asia Trail Master’s race page notes it tends to run hotter and more humid than TMBT up on Kinabalu’s flanks. That shapes everything below: you sweat more, the stations are far apart, and the hills between them are long.
What is confirmed for BUTM 2027?
We checked the official site, borneoultra.com/butm, on 16 October 2026. It confirms:
- Dates: 3 and 4 April 2027. The 100 km, 50 km and 30 km run on Saturday 3 April, the short course (currently about 9 km) on Sunday.
- Start and finish: SMK Tun Fuad Stephens in Kiulu, moved from the riverside park because of bridge construction.
- Final cut-offs: 12 hours for the 30 km, 18 hours for the 50 km (the site calls it 55 km in places), and 34 hours for the 100 km.
- Aid: water and aid stations at roughly 10 km intervals. Fruit, meals and snacks at selected stations, a meal at the halfway station for the 100 km, and a meal at the finish.
- Self-sufficiency: runners must carry what they need between stations, plus a mandatory kit list that varies by category.
What isn’t published yet: exact start times (race buses leave Kota Kinabalu at 3:45am for the 100 and 50 km, so expect a pre-dawn start), intermediate cut-offs, total elevation, and which stations carry food. The organisers say the 2027 courses may change from the 2026 descriptions we’ve used here. Check the racebox downloads before you pack.
Why do 10 km gaps matter more than the distance?
Because on this course 10 km is a unit of time, and time is what decides how much you carry. The 2026 course notes describe one section of the 50 km loop, Lokub (W3) to Kelubaan Lama (W4), as about 12 km with roughly 900 m of climbing and 600 m of descent on sealed road, gravel, track and trail. A mid-pack runner can easily take two and a half hours over that.
The ISSN position stand on ultra-marathon nutrition recommends 450 to 750 ml of fluid an hour during racing, and says needs rise in hot or humid conditions (Tiller et al., 2019). Multiply that by the time to the next station, not the kilometres:
| Time to next station | Fluid at 500 ml/h | Fluid at 750 ml/h |
|---|---|---|
| 1 hour 15 | about 0.6 L | about 0.95 L |
| 2 hours | 1.0 L | 1.5 L |
| 2 hours 30 | 1.25 L | about 1.9 L |
Two 500 ml soft flasks are fine for the flatter road sections near the start. For the long climbs, a heavy sweater needs 1.5 litres or more on board. The course crosses plenty of streams. Don’t drink from them untreated just because you’ve run dry on the ridge above Sinansag.
Your own sweat rate tells you which column you’re in. Do one long run in the midday heat in February or March, weigh yourself before and after, and put the numbers into our sweat rate calculator.
How much should you eat on a hilly trail ultra?
Less per hour than on a road marathon, but for far longer. The ISSN stand suggests 30 to 50 g of carbohydrate and 150 to 400 kcal an hour for ultra-marathons, from a variety of foods, with attention to taste fatigue and the pull towards savoury food later on (Tiller et al., 2019). Jeukendrup’s guidelines go higher, 60 to 90 g an hour for events over two and a half hours, for athletes whose gut has been trained (Jeukendrup, 2014).
In practice: if you’ve trained your gut, aim for 60 g an hour on the 30 and 50 km. If you haven’t, 40 to 50 g is the realistic target, and hitting it every hour matters more than the number. Our guide to carbs per hour for running covers how to build up.
Heat is the complication. Costa and colleagues’ systematic review found gut disturbance reliably appears after about two hours of hard exercise, and that heat stress makes it worse (Costa et al., 2017). Kiulu by late morning is exactly that. Two habits help:
- Eat on the climbs, not the descents. Power-hiking up to Moingob (W2) is the easy time to chew. Running down a slippery rubber-estate track with a mouthful of rice ball is not.
- Front-load before the sun. The first two hours are the coolest of the day. Get 100 to 120 g in while your stomach still cooperates.
Station food isn’t confirmed station by station, so carry all your carbohydrate for the first half and treat anything you’re handed as a bonus. For mixing gels with real food, see gels vs real food at ultra aid stations.
Do you need sodium for BUTM?
For the 9 km, no: water is enough. For every other category you’ll be out well past 90 minutes in lowland heat, so plan sodium and size it to what you actually drink. A starting range is 200 to 550 mg an hour.
Alan McCubbin’s modelling showed sodium replacement matters most when long duration, high fluid intake and salty sweat come together, and matters little when any of those is missing (McCubbin, 2022). A 30 km runner finishing in five hours and drinking 450 ml an hour sits at the low end. A 100 km runner out for 20-plus hours, drinking 700 ml an hour and finishing with white salt lines on the pack straps, sits at the top.
The bigger risk on a long race is drinking far more than you sweat once evening cools things down. The hyponatraemia consensus statement names overdrinking as the main cause of exercise-associated hyponatraemia (Hew-Butler et al., 2015). Drink to thirst after dark. Sodium does not make overdrinking safe; our piece on dehydration vs hyponatremia explains how to tell the two apart.
If you want sodium you can count exactly, our Elec Stamina caplets contain 220 mg each, which slots neatly into a per-station plan. If you’re running the 30 km and don’t sweat salty, salted food from your own bag may be all you need. The full method is in our sodium per hour guide.
What changes on the 100 km?
The 100 km is a figure of eight. The first loop is the 50 km course. You come back through the halfway station at the Kiulu hall, where there’s a meal and the only chance to swap kit, then head out on a second loop that finishes over the same ground as the 30 km, including the rope-assisted stream crossings between Namadan (W9) and The Adventure Centre (W10).
- Eat the halfway meal even if you don’t want it. Twelve-plus hours in, appetite is usually the first thing to go. Sit, eat something salty and starchy, and leave. Ten minutes here can save an hour later.
- Reset your drinking for the night. Sweat rate drops once the sun has gone. Keep drinking at the afternoon rate and you’re overdrinking.
- Save caffeine for when sleep bites. The ISSN stand supports caffeine in the later stages of a race, particularly with sleep loss (Tiller et al., 2019). After midnight, not on the first climb. Our caffeine for ultras guide covers doses.
A worked example: the 50 km in 10 hours
Take a 62 kg Klang Valley runner aiming for about 10 hours in the 50 km. A two-hour midday run on the Bukit Gasing trails gave a sweat rate of 0.9 litres an hour, with faint salt marks on the cap.
- Carried from the start: 1.5 litres of fluid, about 250 g of carbohydrate (gels, two rice balls, a bag of dates), and enough sodium for five hours.
- Per hour: 50 to 60 g of carbohydrate, 600 to 700 ml of fluid, about 400 mg of sodium from food, drink and caplets combined.
- At every station: refill to full, however close the next one looks on the map. Eat whatever fruit is out.
- Before W3 to W4: the full 1.5 litres and something real to eat. This is the longest climb of the day.
The aim isn’t to replace every millilitre. Losing a little body weight over ten hours is normal. Arriving at W4 empty in the midday heat is the failure to plan against.
Before race day
When the 2027 racebox is out, check the start times, intermediate cut-offs and which stations serve food. Then run the whole plan once in training, in the heat, with the same pack. For the wider picture, see our ultra marathon nutrition guide, the ultra drop bag checklist, and our other Malaysian race nutrition guides, including the TMBT fuel plan for the same organisers’ September race.
References
- 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
- 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
- Costa RJS, Snipe RMJ, Kitic CM, Gibson PR (2017). Systematic review: exercise-induced gastrointestinal syndrome, implications for health and intestinal disease. Alimentary Pharmacology & Therapeutics, 46(3), 246-265. doi:10.1111/apt.14157
- McCubbin AJ (2022). Modelling sodium requirements of athletes across a variety of exercise scenarios. European Journal of Sport Science, 23(6), 992-1000. doi:10.1080/17461391.2022.2083526
- Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. (2015). Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference. British Journal of Sports Medicine, 49(22), 1432-1446. doi:10.1136/bjsports-2015-095004
- Borneo Ultra Trail Marathon, official site: General race information, Course maps and profiles and Registration, checked 16 October 2026.
- Asia Trail Master: Borneo Ultra Trail Marathon (MAS), checked 16 October 2026.
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