What to eat before a marathon: Night before to start line

Pre-marathon nutrition isn't complicated. But it does require intention. The decisions you make from the evening before to the moment the gun goes have a direct and measurable impact on how well your glycogen stores are loaded, how your gut behaves in the back half, and whether you arrive at the start line with a cellular energy system that's primed or merely fed.

Here is a complete guide to what to eat before a marathon, starting the evening before and running through to race morning, with the specific timings and portions that the evidence supports.

The evening before: your main glycogen-loading window

Dinner the night before is more important than your race-morning breakfast. Here is why. Glycogen replenishment from a large carbohydrate meal takes three to four hours. Your race-morning breakfast, eaten 60 to 90 minutes before the start, contributes relatively little glycogen by the time you're running. The night-before meal is where you actually fill the tank.

Target 150 to 200g of carbohydrate at dinner, from a refined, low-fibre source. Pasta with a simple tomato sauce is the classic for good reason: high carbohydrate, easy to digest, familiar. White rice with chicken or fish works equally well. The key variables are high carbohydrate, low fat, low fibre, and nothing you haven't eaten before a hard run before. This is not the night for a new restaurant, experimental food, or a heavy meal that will sit in your stomach until kilometre 12.

Eat by 8pm if your race starts before 9am. Add a small carbohydrate snack before bed (a banana, white toast with honey, a small bowl of rice) if you finish dinner early. It will top up your liver glycogen, which gets drawn down overnight to maintain blood glucose while you sleep.

Race morning: what to eat and when

Race morning is not a glycogen-loading event. Your main reserves are already in place. The goal of race-morning food is to top up blood glucose, give your gut something settled to work with, and avoid the reactive hypoglycaemia that can flatten your opening kilometres if you eat at the wrong time.

The evidence-based target is 1 to 4g of carbohydrate per kilogram of body weight, eaten 1 to 4 hours before the start. For a 70kg runner starting at 9am, that means eating 70 to 280g of carbohydrate between 5am and 8am. Most practical meal plans for marathon morning land at 1.5 to 2g per kilogram, eaten 90 to 120 minutes before the start.

Good choices include porridge (oats with water, no full-fat milk), white toast with jam or honey, a banana or two, white rice with a small amount of low-fat protein, or a commercial carbohydrate drink if your gut prefers liquid. Keep fat below 10 to 15g in the race-morning meal. High fat slows gastric emptying and delays the carbohydrate you need from reaching your bloodstream before the start.

 

The timing mistake most marathon runners make

Eating too close to the gun. Many athletes eat their race-morning meal 30 to 45 minutes before the start, triggering an insulin response that drops blood glucose just as the race begins. This reactive hypoglycaemia typically resolves within the first few minutes of exercise as adrenalin overrides the insulin response, but the first kilometre can feel awful: heavy legs, fogged head, energy that doesn't match your training.

Aim to finish your race-morning meal at least 90 minutes before the gun. If you're running an early start and logistics don't allow 90 minutes, keep the meal very small (under 200 calories) and eat it as close to the 15-minute mark as possible. Small quantities eaten within 15 minutes of the start provide a blood glucose boost without triggering a significant insulin response.

Caffeine: the one supplement with clear marathon evidence

Caffeine has robust evidence for endurance performance: it reduces perceived effort, increases time-to-exhaustion, and improves pace in trained athletes. The effective dose is 3 to 6mg per kilogram of body weight, taken 45 to 60 minutes before the start.

For a 70kg runner, that is 210 to 420mg. A double espresso contains roughly 120 to 150mg. A standard pre-workout caffeine capsule or gel with added caffeine can supplement if coffee alone doesn't reach the dose. Habitual caffeine users should maintain their normal intake in the days before the race to avoid withdrawal effects. A brief abstinence of four to seven days before the race (if you can tolerate it) can amplify the race-day effect.

Hydration before the start

Arrive at the start well-hydrated, not aggressively hydrated. 500 to 750ml of water in the two hours before the race is adequate for most athletes in cool conditions. In warm weather, increase this to 750 to 1,000ml and consider an electrolyte drink to avoid diluting your sodium levels before the start.

The final 30 minutes: sip, don't chug. A full stomach at the gun is uncomfortable and slows your early pace. Many experienced marathon runners take a small gel with water in the final 15 minutes before the start to prime blood glucose without the insulin response issue. A 20 to 30g gel is enough.

The cellular layer: what food alone can't do

Carbohydrates provide the substrate for ATP production. But ATP is manufactured in your mitochondria. The efficiency and capacity of your mitochondria determine how well that substrate is converted into the mechanical energy of forward motion, particularly in the closing 10 kilometres when your glycogen stores are declining and the pace demands maximum cellular output.

Gherardi et al. (2024) demonstrated that oleuropein directly activates mitochondrial calcium uptake, a key mechanism in cellular energy production during sustained muscular effort. This is the cellular preparation that sits beneath your carbohydrate strategy, not a replacement for it.

The Pre-Activity Shot, taken 60 minutes before the start alongside your race-morning caffeine and final carbohydrate intake, delivers this cellular priming layer. It is the difference between a mitochondrial system that hits the opening kilometres cold and one that is ready at the cellular level from the first metre of the race.

For more on how race-day nutrition works in practice across the full day, see the complete OLEUS race-day nutrition guide.

Pre-marathon nutrition: a complete timeline

Two days before: maintain higher carbohydrate intake than usual (7 to 10g per kilogram across the day).

Evening before: 150 to 200g carbohydrate at dinner, finished by 8pm; small bedtime snack if needed.

Race morning: 1.5 to 2g carbohydrate per kilogram, eaten 90 to 120 minutes before the start; caffeine (3 to 6mg per kilogram) 45 to 60 minutes before. 60 minutes before: Pre-Activity Shot.

15 minutes before: small gel or sports chew with water if needed to top up blood glucose.

Warm up and race.

Sources

1. Jeukendrup, A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), 25-33. DOI: 10.1007/s40279-014-0148-z

2. Gherardi, G., et al. (2024). Mitochondrial calcium uptake declines during aging and is directly activated by oleuropein to boost energy metabolism and skeletal muscle performance. Cell Metabolism. DOI: 10.1016/j.cmet.2024.10.021

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