What to eat before a marathon: the 3 days before, the night before, and race morning

Your marathon is a few days away. The long runs are done, the taper has started, and the one thing you can still change is what you eat. It matters more at this distance than at any other. A marathon burns more carbohydrate than your body can store, and more than two in five marathon runners hit the wall. What you eat in the three days before the start decides how much fuel you carry to the line and how late in the race the fade begins.

This guide walks the full timeline from three days out to the start line: how many grams of carbohydrate to eat each day for your body weight, a sample carb-loading day, the dinner the night before, the race morning breakfast for early and late starts, and the foods to keep off your plate.

The timeline at a glance

Why the marathon needs a real carb load

A recreational marathon burns about 2,400 to 2,800 kcal, and at marathon pace a large share of that energy comes from carbohydrate. Your muscles and liver can only store a limited amount of it as glycogen. When those stores run low late in the race, the pace drops, the legs feel heavy, and thinking gets foggy. That is the wall. Two things push it back: starting with full glycogen stores and eating carbohydrate during the race. This guide covers the first one.

The evidence is practical, not just theory. In a study of 257 London Marathon runners, those who ate more than 7 g of carbohydrate per kg of body weight the day before the race ran faster and slowed down less in the second half than runners who ate less. A review of carb-loading research found that full glycogen stores delay fatigue by about 20 percent in events longer than 90 minutes and improve race times by 2 to 3 percent. For a four-hour marathoner, 2 percent is almost five minutes.

Half marathon runners can get by with one high-carb day. Marathon runners need the full load, because they will run long enough to empty the tank.

Three days before: keep carbs up, start cutting fiber

Old carb-loading plans started with a depletion phase: three days of hard training on almost no carbs, then three days of loading. You do not need it. Runners who skip the depletion and simply eat more carbohydrate during a normal taper store about as much glycogen, without the misery. Three days out, eat your normal meals and make sure each one is built on rice, pasta, potatoes, bread, or oats. Start easing off the foods that are very high in fiber: beans, lentils, bran cereal, seeded bread, and big salads. Keep your running short and easy.

Two days and one day before: the carb load

The load happens in the last 36 to 48 hours. Sports nutrition guidelines set it at 10 to 12 g of carbohydrate per kg of body weight per day for events longer than 90 minutes. Most recreational runners find that very hard to eat. A target of 8 to 10 g per kg is realistic, still fills the tank, and sits well above the 7 g per kg line from the London study.

Those numbers are big. A normal training day for most runners is 4 to 6 g per kg. The trick is to swap, not stack: bigger carb portions, smaller portions of protein, fat, and vegetables, and some carbs you drink. Here is a sample day for a 70 kg (154 lb) runner.

That is about 610 g, close to 9 g per kg. On the day before the race, move some of the dinner carbs to lunch and the afternoon so you go to bed comfortable.

• Drink some of it. Juice, sports drink, and flavored milk add 30 to 60 g of carbs without filling you up.
• Go white. White rice, white bread, regular pasta, and peeled potatoes give you more carbs with less fiber.
• Keep protein and fat small. They fill you up and leave less room for carbs.
• Salt your food. It helps you hold on to the fluid you drink.
• Snack every two to three hours instead of forcing three huge meals.

Expect the scale to rise 1 to 2 kg by race morning. Glycogen is stored with water, so the extra weight is fuel and fluid you will use in the race. It means the load worked.

The night before: early and ordinary

If you have eaten well for two days, dinner does not need to be special. Eat a normal-sized, carb-based meal you have eaten before a long run: pasta with tomato sauce, rice with chicken or fish, or potatoes with a lean protein. Aim for 2 to 3 g of carbohydrate per kg. Eat 12 to 14 hours before the start so your stomach is empty by bedtime. For a 7:00 am start, that means dinner at about 5:30 to 6:30 pm. Skip cream sauces, fried food, big salads, spicy food, and alcohol. If dinner was early, have a small carb snack before bed.

Race morning breakfast

Overnight, your liver uses a large part of its glycogen to keep blood sugar steady. Breakfast refills it. In one study, runners who ate a carbohydrate meal three hours before a long treadmill run kept going about 9 minutes longer than when they had a placebo, and about 22 minutes longer when they also drank a sports drink during the run.

For a marathon, aim for 1.5 to 3 g of carbohydrate per kg of body weight, 3 to 4 hours before the start. Use the higher end if you can eat early and your stomach is calm, and the lower end if you are nervous or the start is very early.

Keep fat, fiber, and protein low. A small amount of protein, such as an egg or a yogurt, is fine if it is what you normally eat before long runs. Drink 5 to 7 ml of fluid per kg with breakfast, about 350 to 500 ml for most runners, then sip to thirst. Stop large drinks about 45 minutes before the start so you have time for a last toilet stop.

Breakfast timing by start time

Big city marathons often mean a long trip to the start and a long wait in a corral. Pack a second, smaller snack for the start area. Our city race guides, linked at the end, list the start times and what is on each course.

The last hour before the gun

• Coffee: if you drink it every day, have it 45 to 60 minutes before the start. About 3 mg of caffeine per kg of body weight improves endurance performance. For a 70 kg runner that is about 210 mg, roughly two cups of filter coffee. Do not try it for the first time on race day.
• Fluids: small sips only. You cannot fix hydration in the last hour, and a full bladder in the corral helps nobody.
• Final carbs: one gel with water 10 to 15 minutes before the start, or 200 to 300 ml of sports drink. It counts as the first dose of your race fueling.
• Keep your gels where you can reach them and set a timer for the first one.

What not to eat before a marathon

Four mistakes that undo a good carb load

• The giant pasta dinner. One huge meal the night before leaves you bloated and sleeping badly, and it comes too late to matter much. The work is done over two days.
• The healthy high-fiber load. Brown rice, whole wheat pasta, beans, and big salads are great in training. In race week they can mean a toilet stop at mile 16.
• Drinking liters of water the night before. It does not get stored. It wakes you up at night and dilutes your blood sodium.
• Loading and then not fueling. Full glycogen gets you further, not to the finish. You still need carbohydrate every hour of the race.

Then the race: how much to eat during the marathon

Above 60 g per hour, use products that mix glucose and fructose, and only use amounts you have practiced on long runs. The gel guide linked below turns these numbers into a packet count for your pace.

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)Carbohydrate loading of 10 to 12 g/kg per day for 36 to 48 hours; pre-event meal of 1 to 4 g/kg 1 to 4 hours before
2. 2Pre-race Dietary Carbohydrate Intake Can Independently Influence Sub-elite Marathon Running PerformanceInternational Journal of Sports Medicine (Atkinson et al., 2011)London Marathon runners eating more than 7 g/kg the day before ran faster and held pace better
3. 3Carbohydrate-Loading and Exercise Performance: An UpdateSports Medicine (Hawley et al., 1997)Loading delays fatigue by about 20 percent in events over 90 minutes and improves set-distance performance by 2 to 3 percent
4. 4Effect of Exercise-Diet Manipulation on Muscle Glycogen and Its Subsequent Utilization During PerformanceInternational Journal of Sports Medicine (Sherman et al., 1981)A moderate taper with high carbohydrate raised glycogen as much as the classic depletion method
5. 5The Effect of a High Carbohydrate Meal on Endurance Running CapacityInternational Journal of Sport Nutrition and Exercise Metabolism (Chryssanthopoulos et al., 2002)A carbohydrate meal 3 hours before running extended endurance; adding a sports drink during the run extended it further
6. 6Energy Expenditure and Influence of Physiologic Factors During Marathon RunningJournal of Strength and Conditioning Research (Loftin et al., 2007)Recreational marathoners expended about 2,400 to 2,800 kcal for the race
7. 7Metabolic Factors Limiting Performance in Marathon RunnersPLOS Computational Biology (Rapoport, 2010)More than two fifths of marathon runners experience performance-limiting glycogen depletion