What to eat before a half marathon: the day before, race morning, and the last hour

Your half marathon is this weekend. The training is done and the only thing left to get right is food. It matters more than most runners think. A half marathon is short enough to race hard and long enough to run low on glycogen, which is why so many races fall apart between 16 and 19 km. The right food in the 36 hours before the start is the cheapest speed you will ever buy.

This guide walks the timeline from two days out to the start line, with amounts by body weight, sample meals, a breakfast schedule for early and late starts, and a list of what to keep off the plate.

The timeline at a glance

Two days before: keep it normal

There is no need for a special diet two days out. Eat your usual meals and make sure each one has a solid carbohydrate base: rice, pasta, potatoes, bread, or oats. Training is light in taper, so your muscles are already storing more glycogen than usual. Start easing off the foods that are very high in fiber, such as beans, lentils, bran cereal, and large salads. Drink to thirst and keep alcohol low.

The day before: where the race is set up

This is the day that counts most. Aim for 6 to 8 g of carbohydrate per kg of body weight, spread across the whole day. That is more than a normal day and less than a full marathon carb load. It is enough to fill muscle glycogen when training is light. Get there by making carbohydrate the biggest part of every plate and adding carb-based snacks and drinks, not by eating one giant dinner. If you expect to be on the course for more than two hours, go higher, 8 to 10 g per kg. The half marathon carb loading guide linked below has the full protocol.

Here is a sample day for a 65 kg runner that lands near 480 g of carbohydrate without feeling stuffed.

Expect the scale to go up 0.5 to 1 kg by race morning. Every gram of glycogen is stored with about 3 g of water. That weight is fuel and fluid you will use in the race. It is a sign the plan worked.

The night before: early, familiar, not huge

If you have eaten well all day, dinner only needs to be a normal-sized, carb-based meal: pasta with tomato sauce, rice with chicken or fish, or potatoes with a lean protein. Eat early, 12 to 14 hours before the start, so your stomach is empty by bedtime. Salt your food. Skip cream sauces, fried food, big salads, spicy dishes, and alcohol. If dinner was before 6 pm, a small carb snack an hour before bed helps.

Race morning breakfast

You wake up with liver glycogen down by about half after the overnight fast. Breakfast puts it back. Aim for 1.5 to 2.5 g of carbohydrate per kg of body weight, 2.5 to 3 hours before the start. Go toward the lower end if you have a nervous stomach and the higher end if you expect to be out there for more than two hours.

Keep fat, fiber, and protein low. A little protein is fine, such as an egg or a small yogurt, if that is what you normally eat. Drink 400 to 600 ml of fluid with breakfast, then sip to thirst. Stop large drinks 45 minutes before the start to give yourself time for one last toilet stop.

Breakfast timing by start time

The closer to the start you eat, the smaller and simpler the meal must be. Two hours out, stay near 1 g per kg and keep it to white bread, jam, banana, and sports drink. Setting a 4:30 am alarm for a bagel feels silly. It is still worth it.

The last hour

• Coffee: if you drink it daily, have it 45 to 60 minutes before the start. About 3 mg of caffeine per kg of body weight improves endurance performance. That is one to two cups for most runners. If you never drink coffee, race day is not the day to begin.
• Fluids: small sips only. You cannot fix hydration in the last hour, and a full bladder on the start line helps nobody.
• Final carbs: one gel with a few mouthfuls of water 10 to 15 minutes before the gun, or 200 ml of sports drink. This is part of your race fueling, taken early.
• Warm up easy and keep your gels where you can reach them.

What not to eat before a half marathon

Do you need fuel during the race?

For most runners, yes. Breakfast and glycogen cover the first hour or so. After that, taking in carbohydrate keeps pace from fading. How much depends on how long you will be running.

The five most common mistakes

• The giant pasta dinner. One huge meal the night before leaves you bloated and sleeping badly. Spread the carbs across the day.
• Skipping breakfast because of nerves. If solids will not go down, drink your breakfast: sports drink, juice, and a banana still count.
• A healthy high-fiber day before. The salad and the grain bowl are great on any other day.
• Trying the expo samples. New gels, new bars, and new drinks belong in training.
• Drinking litres of water the night before and the morning of. It does not store. It only wakes you up at night and dilutes blood sodium.

Frequently asked questions

Sources

1. 1Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and ACSM: Nutrition and Athletic PerformanceJournal of the Academy of Nutrition and Dietetics (Thomas et al., 2016)Pre-event meal of 1 to 4 g/kg 1 to 4 hours before; pre-exercise fluid of 5 to 10 ml/kg; caffeine at about 3 mg/kg
2. 2Carbohydrates for Training and CompetitionJournal of Sports Sciences (Burke et al., 2011)General fueling up of 7 to 12 g/kg per day for events under 90 minutes; carbohydrate loading for longer events
3. 3A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During ExerciseSports Medicine (Jeukendrup, 2014)Carbohydrate per hour by event duration: 30 g for 1 to 2 hours, up to 60 g for 2 to 3 hours
4. 4Carbohydrate Loading in Human Muscle: An Improved 1 Day ProtocolEuropean Journal of Applied Physiology (Bussau et al., 2002)One day of high carbohydrate intake with rest is enough to raise muscle glycogen to very high levels
5. 5Gastrointestinal Complaints During Exercise: Prevalence, Etiology, and Nutritional RecommendationsSports Medicine (de Oliveira, Burini, and Jeukendrup, 2014)Fiber, fat, and unfamiliar foods as causes of race-day gut problems