Races aren't lost at the finish.
They're lost at mile 18.
The truefuels system is built for what happens after the easy miles run out.
Informed Sport certified · Built by Alistair Brownlee · 4.86★ (200+ reviews)
60–90% of endurance athletes underfuel.
The wall, cramp and overheating are fuelling failures — not fitness failures.
Hitting the Wall
The wall happens because glycogen runs out. At marathon pace you have roughly 90 minutes worth in your muscles and liver. When stores deplete, blood glucose falls. Your brain — which runs exclusively on glucose — fails first: confusion, loss of focus, that feeling that your target pace is impossible to hold. Most runners hit the wall not from lack of fitness, but because they haven't trained their gut. The gut is a trainable organ.
Energy Gels
The truefuels 1:1 glucose:fructose ratio activates two transport pathways simultaneously — SGLT1 for glucose, GLUT5 for fructose — absorbing up to 1.75g/min versus 1g/min from glucose alone. Over a 4-hour marathon that unlocks the equivalent of three extra gels. Start at 30-40g carbohydrate per hour. Add 10-15g per week. Within 6-8 weeks your gut processes 80-90g/hr without distress — the rate that keeps glycogen stable through the final miles.
Shop NowCramps
Cramps don't come from lactic acid. Current sports science points to altered neuromuscular control driven by electrolyte depletion — sodium and potassium specifically. When levels drop low enough, nerve signals become dysregulated. The calf seizes. The hamstring locks. Athletes lose up to 1,840mg of sodium per hour through sweat. A three-hour marathon without electrolyte replacement means a massive deficit by the finish — and water alone makes it worse by diluting what's left.
Electrolytes
390mg of sodium per sachet — matched to what your body actually loses in sweat, not inflated. Your hydration stays on track, from the first mile to the finish. Make electrolytes a daily habit. One sachet in water on waking on training days. One per hour during sessions over 60 minutes. One after training. That's the protocol that stops the cramp at km 35.
Shop NowHeat
For every calorie of work done during exercise, three to four calories of heat are generated. In cool conditions sweating manages this. In warm conditions it cannot keep pace — core temperature climbs, performance drops 5-10%.
CoreCtrl
CoreCtrl is heat preparation. Taken in the days before a hot race or during heat training, it helps your body manage thermal load. Try it for a week and see how your sessions respond.
Shop NowYour Race Fuelling Calculator
Enter your race details and get a personalised gel and electrolyte plan.
Products & Bundles
Start with a bundle or build your own stack. Bundles save you vs buying separately.
RACE READY SYSTEM
40× Energy Gels + 20× Electrolyte sachets + 8× CoreCtrl sachets + FREE truefuels bottle
TRAINING BUNDLE
20× Energy Gels (mixed low + high salt) + 20× Electrolyte sachets
Gel — Low Salt (0.25g)
40g carbs · 0.25g salt · cool conditions · training
Gel — High Salt (1g)
40g carbs · 1g salt · hot weather · heavy sweaters
Electrolytes
400mg sodium · 150mg potassium · 25mg magnesium
CoreCtrl™
4,000mg taurine · cramping + heat management
The Science
Energy Gels
Glucose uses SGLT1. Fructose uses GLUT5. The 1:1 ratio activates both transport pathways simultaneously — absorbing up to 1.75g/min versus 1g/min glucose alone. Over a 4-hour event that unlocks the equivalent of three extra gels. Start at 30-40g/hr and build 10-15g per week. The gut adapts to what you train it to handle.
Shop NowElectrolytes
400mg sodium + 150mg potassium + 25mg magnesium — matched to sweat loss profile." potassium + 25mg magnesium per sachet — matched to sweat loss during endurance exercise. Not just for races. The daily habit that keeps neuromuscular function intact through a training week and eliminates the compounding deficit that causes race-day cramps.
Shop NowCoreCtrl
4,000mg taurine shown to reduce exercise-induced cramping (Peel 2024). Potassium + magnesium support neuromuscular signalling under fatigue. Taken daily in training, not just on race day. This is how you arrive at the start line with reserves intact.
Shop Now
"I built truefuels because I needed a system that worked at Kona — heat, pace, everything against you. This is it."
— Alistair Brownlee, 2x Olympic Champion, truefuels co-founder
Alistair built truefuels because no existing product met the demands of elite triathlon — heat, duration, GI stress all at once. Tested by Alistair and 50+ elite athletes.
Real Fuel. Real Sessions.
★★★★★ 4.86 from 200+ verified athletes
During last weekends Bath Beat Cross Country marathon, I hit the wall around 18-19 miles in, I was ready to through the towel in, my legs had had it,(the temperature was 22 degrees) I was running this after running the Paris Marathon less than two weeks earlier, I drank some of the true fuels electrolytes followed by your energy gel with 1g, within 4-5 min I really started to feel better and went on to finish the marathon feeling good at the finish! I normally use SiS , but will be using Truefuel from now on!! And will be taking these to the Ironman world championships in Kona in October.
Used during the Paris Marathon 2026. Never cramped, got a stitch, or had any stomach discomfort, which I’ve had with other gels.
Really easy to open and take whilst on the move. I struggle with gels but these have not upset my tummy and seem to be helping with performance. I used them for a half marathon trail race, took them in water the day before too. Finished 4th in V40 female category and 30th overall and had no tummy issues. Excited to see how they support me at London 2026
I’ve been using the truefuels products for a few months now during marathon preparation. They’ve been absolutely brilliant. Felt strong throughout. They are light and sit in the stomach well! Highly recommend
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Frequently Asked Questions
Start fuelling at 45–60 minutes. Take a gel every 30–45 minutes after that. Don't wait until you're tired.
2–3 gels. Use the calculator with your target finish time.
60–90g per hour for efforts over 90 minutes. Two gels per hour hits the upper end.
Yes — and you should. The gut needs training to absorb at 80-90g/hr. Using truefuels on long training runs builds that tolerance. Race day is not the place to experiment with fuelling.
Most GI issues with gels come from fructose-only or high-fructose formulas. The 1:1 glucose:fructose ratio in truefuels reduces gut stress by splitting the absorption load across two transport pathways. Start at one gel per hour and build gradually.
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