Ultra-Trail Snowdonia is one of the toughest one-day races in the UK calendar. Steep climbs, technical descents, unpredictable Welsh weather and the sheer time on feet — most athletes spend 8 to 20+ hours moving — turn fuelling into the single biggest controllable variable on race day. Get it right and you finish strong. Get it wrong and the race ends before the climbs do.

This guide breaks down the fuelling strategy our nutritionists use with athletes preparing for UTS, from race-week preparation through the final climb back to Llanberis. Concrete numbers, proven products, and the protocol that lets your body actually absorb the fuel you put in.

Key points

  • Aim for 60 to 90g of carbs per hour — gut-trained athletes can push 90 to 120g/h.
  • Drink 500 to 1,000ml of fluid per hour with 500 to 1,000mg of sodium per hour.
  • Use dual-carb sources (glucose + fructose) to absorb more without GI distress.
  • Fuel from the first 30 minutes — don't wait for hunger or low-energy signals.
  • Switch in real food (sandwiches, salted potatoes, rice cakes) after hour 4 to fight palate fatigue.

Why fuelling makes or breaks UTS

UTS isn't a race where you can wing it with nutrition. The combination of technical terrain (Crib Goch's exposed scrambles, the long Carneddau ridge, the relentless climbs and descents on every loop), 8 to 20+ hours of moving, and 3,000 to 7,000m of vertical gain means glycogen burns through fast.

Once muscle and liver glycogen drop below threshold, performance falls off a cliff. You slow, decision-making fades, and recovery becomes hours away — not the kind of position you want on a Welsh ridge in a storm. Fuelling early and consistently keeps the engine running before the wall has a chance to appear.

How many carbs per hour for UTS?

The headline number is 60 to 90g of carbs per hour. Faster athletes on the shorter UTS distances (50K, 100K) can push toward the upper end. Slower athletes on UTS Plus (165K) or those running into a second night typically settle at 60 to 75g/h to protect the gut over many hours.

The science is settled here. Studies by Jeukendrup (2014), Currell & Jeukendrup (2008), and Stellingwerff & Cox (2014) all show that combining glucose with fructose in roughly a 2:1 ratio lets the body absorb significantly more carbohydrate per hour than glucose alone — up to 90g/h vs ~60g/h with glucose only. This is the reason STYRKR's GEL50 and MIX+ both use a dual-carb formula.

The STYRKR fuelling system for UTS

A simple, race-tested setup:

  • GEL50 dual-carb energy gels — 50g of carbs each, glucose-fructose for fast absorption. 1 to 2 gels per hour.
  • MIX+ drink mix — 40g of carbs and electrolytes per 500ml serve. Pour into your soft flasks at every aid station.
  • SLT+ high-strength electrolyte supplement — for sodium pre-loading and high-loss athletes. 1 in the hour before the start, then 1 per 90 minutes during the race.
  • BAR50 energy rice bars — 30g of carbs per bar, easy to chew on climbs. Use these every 60 to 90 minutes for satiety and to break up the gel monotony.

Test this combination in your final 3 to 4 long training runs. UTS race day is not the time to debut a new fuel.

STYRKR MIX+ being mixed into a bottle for an ultra training session

Pre-race fuelling: race week and race morning

Race week

  • 2 to 3 days out, eat 8 to 10g of carbs per kg of body weight per day. A 70kg athlete: 560 to 700g of carbs daily, mostly from rice, pasta, bread, potatoes and bananas.
  • Cut fibre 24 hours before the start. White rice, white bread, white pasta — the lower the residue, the cleaner the gut on race morning.
  • Pre-load sodium with one SLT+ in the hour before bed and another in the hour before the start.

Race morning

  • Eat your main breakfast 2 to 3 hours before the gun. 100 to 150g of carbs from low-fibre staples — porridge with honey and banana, bagels with jam, or white toast and peanut butter. Whatever you've trained on.
  • Sip a MIX+ drink mix (40g of carbs) in the 30 minutes before the start.
  • Avoid fizzy drinks, large coffees and anything new.

During the race: hourly fuelling cadence

The single rule: take in 60 to 90g of carbs per hour from the first 30 minutes onwards. Don't wait for hunger or low-energy signals — by the time you feel them, you're already 30 minutes behind on absorption.

A practical hourly rotation:

  • Every 30 minutes: one GEL50 (50g carbs) with 100 to 200ml of plain water from your soft flask.
  • Continuously: sip a MIX+ bottle for steady carb + electrolyte intake (40g per 500ml).
  • Every 60 to 90 minutes: one BAR50 (30g) for chew + satiety variety.
  • Every aid station: top up MIX+ and water. Take in salty broth or salted potatoes if available.

Hydration and electrolytes for UTS

Sweat rates on UTS vary wildly with weather. In the cold and wet, expect 400 to 600ml/h. In summer heat, 800 to 1,200ml/h. Sodium losses range from 200 to 2,000mg per litre of sweat — if you're a salty sweater (white salt rings on your kit, eye-stinging sweat), you're at the higher end.

Target: 500 to 1,000ml of fluid per hour with 500 to 1,000mg of sodium per hour. SLT+ pre-loaded plus a MIX+ flask covers most athletes. Heavy salty sweaters add a second SLT+ during the race.

Real-food strategy for ultras

For UTS Plus (165K) or anyone over 8 hours, gels alone don't cut it. Palate fatigue (sweet aversion) kicks in around hour 4 and the gut craves something different.

What works:

  • Salted potatoes — boiled, with extra salt. Aid stations often have these.
  • Sandwiches — peanut butter on white bread, jam sandwiches, salted ham wraps.
  • Rice cakes — homemade or store-bought, salted, with a dab of jam.
  • Fruit — bananas (25g carbs each), dates (16g per Medjool).
  • Sweet/savoury rotation — alternate sweet (gels) with savoury (potatoes, broth) every 90 minutes to keep eating.

Crewing and aid station execution

If you have a crew, brief them on your fuelling plan in writing before race day:

  • Pre-prepared bottles with MIX+ already mixed.
  • A small pouch of gels, bars and tabs ready to hand over.
  • Specific aid station times and what to deliver at each.

Don't rely on thinking clearly mid-race — by hour 8, decision-making is impaired. The crew's job is to remove choices, not present them.

Fuelling the final push

In the last 4 to 6 hours of UTS, your appetite will drop and the gut will resist food. Your job is to keep eating anyway.

Discipline rules:

  • Switch to liquid calories (MIX+, broth, gels) if solids are off.
  • Add 100 to 200mg of caffeine via a caffeinated gel in the final 2 hours — research shows it reduces perceived effort and pushes back fatigue.
  • Don't try anything new — stick to the products that worked in the first 12 hours.

Deep dives: take each piece further

This guide covers the full UTS fuelling system at high level. Each of the following deep dives goes further on a single piece of the protocol:

Final word

UTS Snowdonia rewards athletes who treat fuelling as a discipline, not an afterthought. Carbs in early and consistently, fluid and sodium matched to your sweat rate, real food when palate fatigue kicks in, and the right products tested in long training runs. None of this is glamorous, but on race day it's the difference between finishing strong and DNF'ing on a Welsh hillside.

Train your fuelling like you train your legs. The race is won (or lost) in the months before the start gun.