How to Fuel a Marathon

Marathon fuelling is mostly about starting early and staying consistent through the race, rather than finding a single perfect product. Waiting until you feel low on energy is the most common mistake, since by then you're already behind and hitting the wall becomes considerably more likely. The good news is that the underlying approach is simple and repeatable: get some carbohydrate in at regular intervals, pair it with fluid, and rehearse the exact plan in training so nothing on race morning is a surprise. Most of the real work happens well before the start line, on the long runs where you figure out what your stomach can actually handle at marathon pace, not on the day itself.

Why the marathon is different

Glycogen stores generally last somewhere around 90 minutes to two hours of continuous running for most people, well short of the time most recreational runners spend covering marathon distance. That gap is exactly why fuelling during the race matters so much more here than for shorter distances, where finishing before glycogen runs low is much more realistic. A 5K or 10K is usually over before stored glycogen becomes the limiting factor; a marathon, for most recreational finishers, is not. Once those stores run low, pace usually drops sharply and running starts to feel far harder than the effort should justify, which is the physical sensation behind hitting the wall. Fuelling during the race is simply a way of topping up that supply before it runs critically low, rather than trying to recover once it already has.

A practical timing approach

A commonly used starting point among recreational marathoners is a gel or equivalent quick carbohydrate source roughly every 40 to 60 minutes, starting earlier than feels necessary, often from around 45 minutes into the race. This is a general starting framework, not a fixed rule, and your own tolerance and training will refine it. For a four-and-a-half to five-hour marathon, that works out to somewhere around five to seven fuelling stops over the full distance, which is worth knowing in advance so you can plan how many gels or chews to carry versus rely on aid stations for. Setting a repeating phone alarm or watch alert for your chosen interval on training long runs is a simple way to build the habit before race day, since relying on remembering when you feel like it is exactly the pattern that leads to under-fuelling.

• Start fuelling earlier than feels necessary, generally by 45 minutes to an hour in, even if you feel completely fine
• Aim for roughly one gel or equivalent every 40 to 60 minutes as a starting point, adjusted from what you've tested in training
• Pair gels with water rather than taking them completely dry where possible, since this helps them move through your system more comfortably
• Set a watch or phone alert for your fuelling interval on long runs so the habit becomes automatic well before race day
• Adjust the exact timing and product based on what you've practiced in training, not on what worked for someone else

A sample race-morning fuelling timeline

There's no single correct schedule, but seeing a full timeline laid out can make the abstract every 40 to 60 minutes guidance more concrete. This is one reasonable version for a runner targeting a four-and-a-half to five-hour marathon; treat it as a starting template to adjust after your own long runs, not as a prescription to follow exactly.

Gels, chews, and other options

Gels are the most common choice because they're compact and quick to consume, but chews, sports drinks, and even familiar solid foods work for some runners, particularly on longer training runs. The right choice is largely about what your stomach tolerates and what you'll actually remember to use consistently, not which option is theoretically fastest to digest. Chews take a little longer to eat since you're chewing rather than swallowing a liquid, which some runners actually prefer because it feels more like eating and less like a chore mid-race. Sports drinks handle fuel and fluid together, which can simplify things, but only work well if you're comfortable carrying your own bottle or timing them carefully around aid stations. A smaller group of runners do well on real food, dates, banana pieces, or small bites of familiar snacks, though this generally takes more practice to get portioning and timing right than a gel does.

How fuelling needs differ: half marathon versus full marathon

The core idea, start early and stay consistent, applies to both distances, but the stakes and the exact approach differ. A half marathon for most recreational runners finishes in a window where glycogen stores are stretched but rarely fully exhausted, so fuelling during a half is more about maintaining steady energy than avoiding a hard wall. One or two gels around the midpoint is often enough, and some faster half marathon finishers skip fuelling entirely and feel fine. A full marathon is a different proposition: for the overwhelming majority of recreational finishers, the race takes long enough that stored glycogen genuinely becomes the limiting factor, which is why the every 40 to 60 minute approach matters much more here. If you're moving from half to full marathon training, don't assume your half marathon fuelling habits will simply scale up; treat marathon fuelling as its own thing to practice on your longest training runs, ideally the ones that get closest to your expected finish time.

Test everything in training first

Whatever fuelling plan you land on, test the exact product, brand, and flavour on at least one or two long training runs before race day. Different products can sit very differently, and marathon day is not the time to discover that a particular gel doesn't agree with your stomach. Ideally, test at or close to marathon pace and marathon-length effort, since fuelling that sits fine on an easy recovery run can behave differently once you're running harder and your gut has less spare capacity to work with. If you're planning to use aid station drinks on race day, it's worth trying the same brand in training if you can find it, since the concentration and flavour of sports drinks vary between brands more than people expect.

What to do if your stomach turns on you mid-race

Even with careful testing, stomach trouble mid-race happens; heat, nerves, and dehydration can all make a previously fine product suddenly sit badly. If you feel nauseous or crampy after a gel, the first move is usually to back off, not push through with more fuel. Slow your pace slightly, switch to sipping plain water instead of anything sugary for a few minutes, and let your stomach settle before trying anything else. If a specific product is the clear trigger, switching to plain water and whatever solid food is on offer at aid stations for the rest of the race is a reasonable fallback, even if it means less than ideal fuelling for the remaining distance. Pushing harder on fuel when your stomach is already unhappy usually makes things worse, not better, so treat this as a moment to manage discomfort rather than stick rigidly to your original plan.

Hydration alongside fuelling

Fuelling and hydration work together, and getting one right while ignoring the other still leaves you vulnerable to a rough second half. Taking gels without enough fluid alongside them can make them sit heavier and slower to digest, and being dehydrated on top of low energy compounds both problems rather than simply adding to them. See hydration planning for race day for how much to drink and how to adjust for heat, and carb loading explained for how pre-race eating sets up the fuel you're working with on the day. If you're also using an electrolyte drink or tablets, electrolytes for runners covers how that fits alongside your gel or chew schedule rather than replacing it.

Know what's on the course

Some marathons offer gels or sports drinks at aid stations, others only offer water, and spacing between stations varies by event. Check your specific race's category page for aid station details rather than assuming, since planning around the wrong assumption can leave you short on fuel or water later in the race. If your event does offer gels on course, it's still worth carrying at least one or two of your own tested product as backup, since course-provided gels may be a brand or flavour you haven't tried, and running out of your familiar option is not a good time to experiment. Wider aid station spacing, common on courses that use fewer, larger stations rather than many small ones, also means you may need to carry more fluid or fuel yourself between stops than on a race with closer spacing.

Common marathon fuelling mistakes

• Waiting until you feel low on energy before taking your first gel, rather than starting on a schedule
• Trying a brand-new product, flavour, or brand for the first time on race morning
• Taking gels completely dry with no water, which can make them sit heavily and digest more slowly
• Assuming aid stations will have gels or sports drinks without checking your specific event's category page
• Abandoning fuelling entirely after one bad stomach moment, instead of easing back and adjusting rather than stopping altogether