You’ve done the hard bit.
You entered the London Marathon, you’re ticking off the miles, you’ve invested in decent shoes, kit and time.
But there’s one thing that still trips runners up every single year:
Leaving fuelling to the last minute and grabbing whatever cheap nasty gels are left on the supermarket shelf.
You’ve probably seen it (or done it):
The runner who turns up after just orange juice and a coffee…
The one who feels amazing until mile 10, then suddenly crashes, cramps, or has to dive for the loo because their gels don’t agree with them.
This blog will show you:
-
The #1 fuelling mistake London Marathon runners make
-
What your body actually needs on race day
-
How to fuel smarter with KMC NRG GEL and refillable energy gels so you can run stronger, avoid gut issues and give yourself a real shot at your PB.
The classic London Marathon fuelling mistake
It usually looks like this:
-
You train for months, focused on mileage, pace and strength work.
-
A week or two before race day, panic sets in: “I should probably get some gels…”
-
You buy the cheapest, thickest, most generic gels you can find, having never tried them in training.
-
On race day, you neck them out of fear rather than a plan.
The result?
-
Energy crashes around mile 10–18
-
Stomach cramps, bloating or emergency toilet stops
-
Sticky hands, sticky pockets and plastic wrappers dropped all over the course
-
A long, painful shuffle instead of the finish you trained for
You’ve put in too much work to let that be your story.
What your body actually needs on marathon day
The London Marathon is 26.2 miles of controlled damage. Your muscles are burning through stored carbohydrate (glycogen) from the moment you cross the start line.
To keep running strong, you need:
-
Carbohydrates: around 60–90 g per hour for most marathon runners
-
Electrolytes: especially sodium, to help you absorb fluid and avoid cramp
-
Fluids: to stay hydrated without overdoing it
-
Optionally, caffeine: to help with focus and perceived effort
You can’t cover that demand off orange juice, a coffee and hope.
You need a fuelling plan that’s:
-
Tested in training
-
Easy on your stomach
-
Simple to repeat every 30–40 minutes on race day
Why cheap, generic gels let you down
Traditional mass-market gels have a few big problems:
-
Thick, sickly textures that are hard to swallow at race pace
-
Single-carb formulas that hit hard then fade fast
-
Higher risk of gut issues – bloating, cramp, that horrible sloshy feeling
-
Overly sweet flavours that become unbearable after 3–4 servings
-
Single-use packaging that creates a trail of sticky plastic waste
They technically “do the job”, but they don’t leave you feeling energised, fresh or confident.
A different approach: KMC NRG GEL & refillable energy gels
Now imagine a gel that:
-
Tastes clean and refreshing, not sickly
-
Uses a dual-carbohydrate formula for fast and long-lasting energy
-
Includes all 4 key electrolytes to support hydration
-
Is infused with natural peppermint, helping it feel lighter on your stomach
-
Comes in a refillable format so you cut plastic, not performance
That’s exactly what we built with KMC NRG GEL and our refillable energy gels.
-
Rated among the best energy gels in the UK by outlets like The Telegraph for stomach-friendly, long-lasting energy
-
Trusted by thousands of runners chasing London Marathon PBs and beyond
-
Available in refillable pouches + soft flasks, so you can carry up to multiple gels in a single, easy-to-use flask instead of a belt full of sticky wrappers
When you squeeze a KMC gel mid-race, you’re not just “taking a gel” — you’re topping up the energy, electrolytes and focus you’ve already trained your body to use.
A simple London Marathon fuelling plan (you can adapt)
Every runner is different, but here’s a simple structure to start from and test in training.
2–3 hours before the start
-
Have a carb-rich breakfast you’re used to: porridge, toast, bagel, rice pudding, etc.
-
Sip water or a weak KMC ISO MIX to start topping up fluids and electrolytes.
15–20 minutes before the gun
-
Take 1 × KMC NRG GEL (caffeinated or non-caffeinated depending on your preference).
-
Wash down with a few sips of water.
During the race
Aim for around 60–90 g of carbs per hour from gels and drink:
-
Every 30–40 minutes:
-
1 × KMC NRG GEL, or
-
A good squeeze from your refillable gel flask (each full flask = roughly 2 gels’ worth of carbs).
-
-
Drink little and often:
-
Water + KMC ISO MIX in your bottles or pick up water at aid stations.
-
Don’t smash a whole bottle at once; steady sips work better for your gut.
-
For most London Marathon runners, that works out at roughly 5–7 gels over the race, depending on pace and body size.
After you finish
-
Start sipping ISO MIX as soon as you can.
-
Eat a carb + protein snack or meal within the first hour to kick-start recovery.
The golden rule: practise your race fuelling now
The biggest mistake isn’t just buying cheap gels.
It’s trying anything for the first time on race day.
Your training plans or coach will always tell you the same thing, progress isn't made with one magic session or golden bullet supplement..
Progress comes with being consistent and disciplined.
Your nutrition should be the same.
Instead:
-
Use every long run between now and London to practise:
-
The same breakfast
-
The same timing for gels
-
The same KMC NRG GEL or refillable flavours you’ll use on the day
-
-
Get your stomach used to taking on carbs early and often
-
Notice how much fluid you’re comfortable with per hour
By the time race week arrives, your fuelling should feel boringly familiar. No surprises. No guesses. Just execution.
Don’t let fuelling be the weak link
You’ve:
-
Entered one of the world’s most iconic marathons
-
Put in the miles, the early mornings and the grim winter sessions
-
Invested in your kit, your training plan and your goal
Don’t be the runner who crashes out at mile 10 because they “forgot about nutrition”.
Be the one who:
-
Fuels early, consistently and confidently
-
Chooses gels that are easy on the stomach, not a battle with every squeeze
-
Turns up on race day knowing their plan is tested, not guessed
Fuel smart. Run stronger. Fight fatigue. Recover better.
You handle the training.
We’ll make sure the energy is there when you need it most.