How to Fuel a Long Run (Endurance Nutrition Basics, No Degree Required)

Here is something nobody tells you when you sign up for your first trail race or long run: fitness will only get you so far. At some point, probably around the 90-minute mark, your body stops caring how many kilometres you've logged and starts caring very much about whether you've eaten enough.

That's what endurance nutrition is about. Not supplements, not complicated meal plans, not eating chia seeds every morning and pretending you enjoy it. Just giving your body the fuel it needs to keep going when things get hard.

Here's the basics.

Why your body runs out of energy

Your muscles run on glycogen, which is just stored carbohydrate. The problem is your body can only store about 90 minutes' worth of it at moderate effort. Once it's gone, your legs get heavy, your brain gets foggy, and everything hurts more than it should (including your ego).

This is called bonking, or hitting the wall. It feels like a fitness problem, but it's almost always a fuelling problem. And the good news is it's almost entirely preventable.

The fix: fuel early, fuel often

The most important rule in endurance nutrition is to start fuelling before you feel like you need to. By the time your energy drops, you're already behind. The fuel you take then needs 10 to 15 minutes to kick in, which is a long time to spend shuffling along, wondering why you ever thought this was a good hobby (read: what the hell - did I think this was just a nice day in the mountains - somebody help!).

For any run over75 minutes, start taking on carbohydrates around the 45-minute mark. Then repeat every 45 minutes after that.

What to eat on a long run

In an ideal world, real food would work perfectly mid-run. And sometimes it does. But for most people at a decent effort level, solid food is slow to digest and awkward to carry. That's where purpose-built running nutrition comes in.

Energy gels are the most popular option for a reason. A single GU Energy Gel delivers around 22 grams of fast-absorbing carbohydrates in a small, portable sachet. No chewing, no fumbling, no stopping. It absorbs quickly and gives your muscles what they need within minutes. (If you're new to them, our guide to what's in a GU gel is a good place to start.)

Electrolytes matter too. Sweat takes sodium with it, and sodium plays a bigger role in how you feel and perform than most people realise. Sipping an electrolyte drink or using a hydration tablet alongside your gels keeps everything in balance.

A simple fuelling framework for beginners

•        Run under 60 min at easy effort: water only, no extra fuel needed

•        Run 60 to 90 min: one gel at the 45-minute mark, water throughout (but this isn't always necessary)

•        Run over 90 min: one gel every 45 minutes from the start, sip water every 15 to 20 minutes

•        Race day: do exactly what you practised in training. Not the time for experiments.

One more thing

Your gut needs practice, too. The first time you take a gel at race pace, your stomach might be less than thrilled. Your mouth wondering what this high-viscose stuff is. That's normal. Use gels on your long training runs consistently, and your body adapts. By race day, it becomes routine.

Endurance nutrition sounds complicated, but the basics are simple: start early, stay consistent, and don't wait until you're already suffering. That's it.