Most marathon fuelling advice is written for a runner who'll be finished in three or four hours. If you're going to be out there for six, that advice doesn't just fall a bit short — it's built around a different problem.
Here's the difference in one sentence: a faster runner is solving a sharp, two-to-three-hour fuelling problem; you're solving a long, steady, all-day one. More hours means more total fuel, a stomach that has to keep working long after a quicker race would be over, and a pace gentle enough that you can actually eat real food along the way. Each of those changes the plan.
More hours, more total fuel
The usual guidance is to take in somewhere around 30–60 grams of carbohydrate an hour on a long effort. The headline number isn't wildly different for you — but you're doing it for six hours instead of three, so the total roughly doubles. That's a lot to carry, a lot to remember, and a lot for your gut to process. It needs planning, not improvising at the start line.
The practical move is to decide before race day roughly what you'll take and when — an amount per hour you know your stomach is happy with — rather than guessing on the day. Treat it like part of the plan, the same as the route.
Your slower pace is an advantage here
This is the part nobody tells slow runners: going easier means you can eat things a faster runner can't keep down. When you're not redlining, blood isn't being pulled away from your stomach as hard, so real food becomes an option — a sandwich, a banana, a few salted potatoes, whatever sits well. Gels are convenient, but you don't have to live on them for six hours, and most people are glad not to.
A mix tends to work best: something real when you fancy it, something quick when you don't. The goal is steady fuel you'll actually take, not the theoretically perfect product you'll be sick of by hour three.
Practise it — your gut is trainable
The single biggest fuelling mistake is trying a new plan for the first time on race day. Your stomach handles fuel better when it's used to working while you move, and that's something you build in training. Use your long time-on-feet runs to rehearse exactly what you'll eat and drink on the day, in the same amounts. By race week you want a plan your gut already knows.
Walk breaks make eating easier
If you're running walk-run — and for a long, slow marathon you probably should be — your walk breaks are the natural moments to take on food and drink. It's far easier to eat a few bites while walking than to wrestle a gel open mid-stride. Lining your fuelling up with your walk intervals turns "remembering to eat" into a simple rhythm. (More on the rhythm itself in our walk-run marathon plan.)
Don't forget the drinking
Over five-to-seven hours, hydration follows different maths than a quick race — more total fluid, electrolytes that matter more, and aid stations that may be packed up before you reach them. It deserves its own attention; a dedicated hydration guide is on the way.
A simple way to start
You don't need a spreadsheet. Pick an amount of carbohydrate per hour your stomach is comfortable with, decide what mix of real food and gels you'll carry, practise it on your long runs, and tie your fuelling to your walk breaks so it happens on rhythm. Adjust to your own body — everyone's gut is different, and the plan that works is the one yours is happy with.
For the full picture of training, fuelling, and race-day logistics, see the slow marathon pillar guide.
If you'd like the hour-by-hour version — a practical fuelling plan you can take to your next long one, plus a printable race-day card — our free Slow Finisher's Fuelling Guide lays it all out. Join the list below and we'll send it over.
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