Marathon Fueling Strategy Example for Race Day

The marathon is rarely decided by one dramatic mistake. More often, performance slips because an athlete starts well fuelled, then takes the first gel too late, drinks reactively, and reaches 30 km trying to repay an energy debt. This marathon fuelling strategy example gives you a clear race-day structure: carbohydrate before and during the race, fluid matched to conditions, and sodium delivered with intent.

It is written for a runner targeting a marathon of around 3:30 to 4:15. The principles also work for faster and slower runners, but the details must be adjusted to your expected time on feet, your sweat rate, weather, aid-station access and, above all, what your gut has already tolerated in training.

"The runners who fade at 32 km are rarely unfit. They're underfuelled — from a first gel that came too late, a drink that came from the wrong station, a sodium plan that was never rehearsed in heat. Write the schedule. Set the alerts. Run the plan you built, not the one you invent when you're tired."
— Alistair Brownlee, Two-time Olympic Triathlon Champion and founder of truefuels

Start with the numbers that matter

For most marathon runners, the target during the race is 60–90 g of carbohydrate per hour. That range is not a challenge to force-feed. It is a performance target to build towards. If you currently tolerate 40–50 g per hour, repeatedly practising 60 g per hour is more valuable than attempting 90 g for the first time on race day.

The upper end works best when your fuel uses multiple transportable carbohydrates, typically glucose and fructose, and when your gut has been trained to absorb it. At 90 g per hour, you are taking in a meaningful amount of energy under stress. Product choice, concentration and timing all matter.

Fluid is more individual. A useful starting range is 400–800 ml per hour, with the lower end often suitable in cool conditions and the higher end more likely in heat or for heavier sweaters. Sodium requirements commonly sit between 300–800 mg per hour, but can be higher for athletes with salty sweat, long race times or hot conditions. Do not copy another runner's bottle plan without understanding the conditions behind it.

The objective is not to replace every gram of sweat lost. It is to avoid excessive dehydration while also avoiding overdrinking. Drinking beyond thirst and need can dilute blood sodium and create a serious problem. Use your training data, take drinks steadily, and let conditions change the plan.

truefuels Performance Gel

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Marathon fuelling strategy example: a 3:45 race

A 3:45 marathon requires controlled execution for almost four hours. The example below targets 75 g carbohydrate, around 550 ml fluid and 500 mg sodium per hour in mild conditions. That is 280–285 g carbohydrate across the race, excluding your pre-race meal.

Assume your gels provide 25 g carbohydrate each and your drink provides 30 g carbohydrate plus 400–500 mg sodium per 500 ml. If your own products differ, retain the hourly targets and recalculate the servings. Do not assume every gel or electrolyte sachet delivers the same amount.

Three to four hours before the start

Eat 1–3 g carbohydrate per kg of body mass, depending on your appetite and how close to the start you are eating. A 70 kg athlete might take 100–140 g carbohydrate from familiar, low-fibre foods: porridge with banana and honey, white toast with jam, or rice with yoghurt if that is already part of their routine.

Keep fat, fibre and heavy protein modest. The purpose is to top up liver glycogen after the overnight fast without creating a full stomach at the start line. Sip 400–600 ml fluid during this period, ideally including some sodium if conditions are warm or you tend to wake dehydrated.

Fifteen minutes before the gun

Take one 25 g gel with a few mouthfuls of water. This is not compulsory if you are prone to nausea, but it is a useful final carbohydrate top-up for many runners. It also gives you a simple timing anchor: you begin fuelling before fatigue, not once you feel you need rescuing.

From 0 to 60 minutes

Take one gel at 20 minutes and another at 40 minutes. Drink about 250–300 ml during the hour, split across aid stations rather than swallowed in one go. If you are carrying a carbohydrate-electrolyte drink, aim to finish roughly 500 ml across the first hour and reduce the number of gels only if that drink carbohydrate is included in your total.

For this example, the first hour could be two gels at 25 g each plus 500 ml drink at 30 g. Total: 80 g carbohydrate and approximately 450 mg sodium. Starting early keeps blood glucose more stable and prevents the common late-race pattern of chasing energy with large, poorly timed doses.

From 60 to 150 minutes

Continue the same rhythm: a gel every 20 minutes, with steady drinks. By this stage, aid stations can become crowded and concentration can drift. Make your plan operational. Know which stations you will drink at, whether you are carrying bottles, and where spare gels sit in your shorts or belt.

If the race supplies a sports drink, only use it as a primary fuel source if you have trained with it and know its carbohydrate and sodium content. An unknown drink can turn a precise plan into guesswork. Carrying your own measured fuel gives you control; relying on course provision can reduce what you carry. The right choice depends on your tolerance for logistics versus uncertainty.

At 90–120 minutes, assess execution rather than searching for sensations. Are you still hitting the schedule? Have you missed a drink because an aid station was congested? Is the day warmer than forecast? Small corrections now are easier than trying to recover at 32 km.

From 150 minutes to the finish

This is where a plan earns its place. Continue taking carbohydrate every 20 minutes unless you are so close to the finish that another serving will not be useful. Do not stop fuelling simply because your stomach feels settled or because the finish feels near. Marathon pace becomes more expensive as glycogen availability falls and muscle damage accumulates.

If you struggle with sweetness late in the race, solve that in training. Some athletes tolerate a less sweet gel, a lightly flavoured drink or water alongside fuel better than repeated concentrated flavours. Do not replace carbohydrate with plain water, however. Flavour fatigue is real, but energy needs do not disappear.

In a 3:45 race, you may take a final gel around 3:20–3:25. That dose can still support the final 20 minutes. The total race intake would be about nine gels, including the pre-start gel, plus 1.5–2.0 litres of carbohydrate-electrolyte drink. Adjust the fluid volume upward in heat, but make sure sodium rises with it rather than relying on water alone.

Make hydration conditional, not fixed

Temperature, humidity, wind and sun exposure can change your fluid requirement more than most runners expect. A cool spring marathon may allow 400 ml per hour. A warm, humid race could demand 750 ml per hour or more. Your carbohydrate plan should remain steady where possible; your hydration plan needs greater flexibility.

The most useful field test is a simple sweat-rate check. Weigh yourself before and after a one-hour run at planned marathon effort in representative conditions. Record fluid consumed, then compare body mass change. Repeat on another day because sweat rate varies. This will not create a perfect number, but it gives you a defensible starting point.

Sodium is equally personal. White salt marks on kit, stinging sweat in the eyes, repeated cramping history and large body-mass losses can suggest higher needs, though none is a diagnosis on its own. Athletes with medical conditions, blood-pressure concerns or a history of exercise-associated hyponatraemia should seek individual clinical guidance rather than self-prescribing high sodium intake.

Train the gut as deliberately as the legs

A race-day plan only works if it has been rehearsed under load. Use long runs and marathon-pace sessions to practise the same gel intervals, fluid volume and sodium dose you intend to use on race day. Begin at a tolerable carbohydrate rate, then increase by 10–15 g per hour over several sessions if your gut is calm.

Practise when tired, not only on easy runs. Include at least one long session after a higher-carbohydrate day so you can separate the effect of fuelling during the run from poor preparation beforehand. Also rehearse practical details: opening gels with cold hands, carrying bottles, taking fuel while running at pace and drinking from cups without losing half of it.

A structured system such as truefuels can make that rehearsal simpler because the carbohydrate and electrolyte delivery are clear. But the principle remains the same with any product: calculate the intake, repeat it in training, and arrive knowing exactly what each serving contributes.

The mistakes that flatten good runners

The first is waiting for hunger. Hunger is not a reliable marathon fuelling alarm, and low energy availability often arrives before you feel it. The second is treating gels as emergency treatment rather than scheduled intake. The third is taking gels without enough fluid when the product requires water, which can increase gastrointestinal discomfort.

Another common error is changing everything for a hot forecast. You may need more fluid and sodium, but doubling gel intake without a carbohydrate target can overwhelm the gut. Keep your carbohydrate rate measured, increase fluids progressively, and use electrolyte delivery to support the larger fluid intake.

Race day should feel controlled, not improvised. Set your watch alerts if they help, label bottles, pack one more gel than you expect to need, and give every kilometre a job. When the final 10 km demands your full attention, the best fuelling plan is the one you have practised so often that you simply keep moving and take the next dose.

The complete marathon fuelling system. Carbohydrate, sodium and heat regulation, planned by hour.

Performance Gel, Active Hydration and CoreCtrl — 40 gels, 40 electrolyte sticks, 8 CoreCtrl sachets. Every part of the protocol covered, built by Alistair Brownlee and tested at the highest level of triathlon.

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