TL;DR
A GU Energy gel is a small sachet of fast-absorbing carbohydrates that tops up your fuel stores mid-run without the digestion hassle of real food. If you're running over 75 minutes at any decent effort, gels are worth taking seriously. Under 30 minutes at an easy pace, eat a banana and move on.
Let's be honest. The first time most of us saw someone squeeze a mystery packet into their mouth mid-run, it looked deeply unpleasant. A bit of squinting. A slight grimace. Then they just... carried on running. Faster, somehow.
So what is that stuff? And should you be doing it too?
The short version
A GU Energy gel is a small sachet of fast-acting carbohydrates: the primary fuel your muscles burn during exercise. Runners might call them ‘running energy gels’. Whether it’s running, swimming or cycling, when your energy stores start running low (usually around the 60 to 90 minute mark), a gel tops them back up quickly so you can keep moving without your legs staging a protest.
Think of your body like a car with a small performance fuel tank. It's fast-burning, efficient, and great for hard efforts, but it doesn't hold much. Gels are how you refuel on the go, without pulling over.
What's inside GU Energy gels?
They’re not baby food. Mostly:
• Carbohydrates (maltodextrin + fructose) - the actual energy. The blend of two types means your gut can absorb more, faster, without cramping. Science, but the useful kind.
• Sodium (some flavours) - you sweat it out, gels help put a little back. Also helps the carbs absorb properly, which is a bonus.
• Amino acids (in some flavours) - help reduce muscle breakdown on longer efforts.
• Caffeine (in select flavours) - optional, but effective. Roughly half a cup of coffee per gel. We'll save the full caffeine conversation for another day.
Do I actually need energy gels?
It depends on how long you're out there. For a quick 30-minute jog? No. You'll be fine. Eat a banana afterwards and carry on.
But for anything over 75 to 120 minutes at a solid effort: trail runs, long training sessions, race day, yes, gels are worth taking seriously. The athletes who bonk (that joyless experience of your legs turning to cement and your brain going offline, we’ve all been there) are almost always the ones who skipped fuelling or left it too late.
"Don't wait to feel flat. Top up from the start." Fuelling isn't a rescue plan. It's a strategy.
Why choose GU?
We've tested a lot of energy gels. GU has been around since 1993, the formulations are well-researched, and - this matters more than people admit - they actually taste good. When you're 4 hours into a run, and your relationship with food is complicated, "tastes fine and stays down" is high praise.
GU also makes it easy to build a consistent fuelling habit, which is really what this is all about.
Do GU Energy gels sound like a fit for your exercise routine? Order now and get 10% off your first order.
Next up: why energy gels actually work… The short version, no textbook required.
Frequently Asked Questions
What is actually inside a GU Energy gel? ▼
Mostly carbohydrates — a blend of maltodextrin and fructose that absorbs quickly without overwhelming your gut. Depending on the flavour, you'll also find sodium (helps replace what you sweat out and aids carb absorption), amino acids (reduce muscle breakdown on longer efforts), and caffeine in select flavours — roughly the equivalent of half a cup of coffee per gel.
Do I actually need energy gels? ▼
For runs under 60 minutes at an easy pace, no. For anything over 75–120 minutes at a solid effort — trail runs, long sessions, race day — yes. Athletes who bonk mid-race almost always skipped fuelling or started too late. Gels are how you stop that from happening.
Why not just eat real food instead? ▼
During exercise, your body redirects blood away from your digestive system to your working muscles — great for performance, terrible for processing food. Gels are formulated to absorb quickly without a long digestive queue. Real food works for some athletes at slower efforts, but for most people racing at pace, gels are more reliable and a lot less messy.
Why GU specifically? ▼
GU has been around since 1993 with well-researched formulations, a wide flavour range, and — this matters more than people admit — they actually taste good. When you're 4 hours into a run and your relationship with food is complicated, "stays down and tastes fine" is high praise. Consistent fuelling requires a gel you'll actually keep taking.
Are caffeinated gels safe to use? ▼
For most healthy adults, yes. Each caffeinated GU gel contains around 20–40mg of caffeine — roughly half a cup of coffee. If you're sensitive to caffeine or running late in the day, stick to the non-caffeinated flavours. Save caffeinated gels for the back half of long efforts when you need the edge most.
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