What to Eat Before a Half Marathon: From Carb Loading to Gels

The half marathon sits right on the line where sports nutrition advice changes. Races shorter than about 90 minutes don’t call for carbohydrate loading and longer ones do, so a runner finishing in 1:25 and a runner finishing in 2:20 are solving different problems over the same 13.1 miles. Most runners are on the longer side of that line: the median U.S. finisher in 2024 took about 2:13, as the half marathon averages show. This guide covers the two days before, the night before, race morning and the start, with every target scaled to your body weight.

Do you need to carb load for a half marathon?

Carbohydrate loading means eating more carbohydrate than usual while your training winds down, so your muscles store extra glycogen, the fuel they burn fastest at race effort. The joint position statement from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine draws the line at 90 minutes. For longer events it recommends 10 to 12 grams of carbohydrate per kilogram of body weight per day for the 36 to 48 hours before, and for shorter events a normal high-carbohydrate day of 7 to 12 grams per kilogram (Thomas et al., 2016).

The cutoff comes from what happens to glycogen during the race. A review of the loading research found that starting with more glycogen doesn’t help moderate running or cycling that lasts 60 to 90 minutes, because plenty is still left in the muscles at the finish. In events longer than 90 minutes, extra glycogen postpones fatigue by about 20 percent, and high-carbohydrate diets have improved set-distance performance by 2 to 3 percent (Hawley et al., 1997). One of the classic loading studies even used a half marathon: extra carbohydrate raised the runners’ muscle glycogen but didn’t make their treadmill half any faster (Wallis & Podlogar, 2022).

Sports Dietitians Australia still recommend loading over the 24 to 48 hours before a half marathon or longer (Sports Dietitians Australia), and the two positions fit together once you factor in your finish time. If you expect to run under about 90 minutes, a normal carbohydrate-rich day before the race covers you. If you’ll be out there for 1:45, 2:00 or 2:30, a real load is worth doing. If you’re not sure where you’ll land, the half marathon pace chart turns a recent race into a realistic finish time.

Expect the scale to go up a little. Glycogen is stored with water (Wallis & Podlogar, 2022), and Sports Dietitians Australia tell marathoners to expect a gain of 1 to 2 kilograms during a load, which comes back off after the race (Sports Dietitians Australia).

How much carbohydrate to eat the day or two before

The targets are bigger than most runners expect, so it helps to see them in grams.

At 10 grams per kilogram, a 160-pound runner needs about 725 grams of carbohydrate a day, close to 2,900 calories from carbohydrate alone. Getting there means changing what’s on the plate, with more rice, bread, potatoes, cereal and fruit and less fat and protein, rather than simply eating more of everything. Over the last 12 to 24 hours, Sports Dietitians Australia suggest low-fiber foods, fewer high-protein and high-fat foods, and compact liquid carbohydrate (Sports Dietitians Australia). For scale, their marathon fact sheet lists portions that each carry about 50 grams of carbohydrate, including 1 to 2 cups of cereal with a cup of milk and two English muffins with peanut butter (Sports Dietitians Australia).

That’s also why a big pasta dinner the night before isn’t a carb load on its own. It’s a good meal, but a 725-gram target is spread across two days of meals and snacks, not one plate.

The night before

The goal for the last 24 hours is a full tank and a quiet stomach. Somewhere between 30 and 50 percent of athletes report gut complaints during exercise (de Oliveira et al., 2014). Fiber, fat, protein and fructose have all been linked to a higher risk of symptoms, and Asker Jeukendrup, one of the leading researchers on the subject, goes as far as advising athletes to avoid milk products, fiber, and high-fat and high-protein foods for the 24 hours before competition (Jeukendrup).

Runners already do a version of this. In a survey of 388 runners, the foods most often avoided before racing were meat (32 percent), milk products (31 percent), fish and seafood (28 percent), poultry (24 percent) and high-fiber foods (23 percent), and runners who raced longer distances were more likely to cut fiber (Parnell et al., 2020). You don’t have to be that strict, but the night before a race isn’t the time to find out how your stomach handles a new restaurant. A dinner you’ve already eaten before a long run, built around rice, pasta, potatoes or bread with a simple sauce and a lighter hand on salad, beans and anything fried, is the safe choice.

What to eat on race morning

Breakfast matters more than it seems, because your liver spends the night supplying blood glucose. Liver glycogen falls after an overnight fast while muscle glycogen holds steady (Wallis & Podlogar, 2022), so the morning meal tops up the store that keeps your blood sugar steady during the race.

The guideline is 1 to 4 grams of carbohydrate per kilogram of body weight, eaten 1 to 4 hours before the start, from foods low in fat, protein and fiber (Thomas et al., 2016). The closer you eat to the gun, the smaller the meal. Sports Dietitians Australia suggest a light, low-fiber snack 1 to 2 hours before an early start, such as flavored milk with a muesli bar, peanut butter on toast, or crumpets with banana and honey, and a larger meal 3 to 4 hours before a later start, such as porridge with milk and fruit, a rice or pasta dish, or a banana smoothie (Sports Dietitians Australia).

For a 160-pound runner, the range runs from about 75 grams of carbohydrate for a snack an hour out to about 290 grams for a full meal four hours out. Most half marathons start early, so the realistic version is usually a smaller breakfast around 5 or 5:30 for a 7 a.m. gun.

Some of that carbohydrate can come from fruit, honey or jam. One study found that adding fructose to a carbohydrate-rich breakfast improved endurance capacity in trained cyclists compared with a glucose-only breakfast, possibly because the liver handles most fructose and may store more glycogen as a result (Wallis & Podlogar, 2022). Fructose is also on the list of things linked to gut trouble (Jeukendrup), so stick to amounts you’ve tested in training.

Coffee and caffeine

Caffeine is one of the few legal aids with consistent evidence behind it. The International Society of Sports Nutrition puts the effective dose at 3 to 6 milligrams per kilogram of body weight, most often taken about 60 minutes before exercise, and notes that very high doses around 9 milligrams per kilogram bring more side effects without being needed for the benefit (Guest et al., 2021). In one study, 5 milligrams per kilogram made 5K time trials about 1 percent faster for both well-trained and recreational runners (O’Rourke et al., 2008). On a 2-hour half, 1 percent is about 70 seconds.

You may not need anything beyond your normal coffee. At 3 milligrams per kilogram, a 160-pound runner needs about 220 milligrams, and the FDA lists a 12-ounce cup of regular brewed coffee at 113 to 247 milligrams (FDA). Caffeinated gels add it in smaller steps. The caffeinated versions of GU’s gels carry 20 to 40 milligrams each (GU Energy).

People respond differently, though. The ISSN ties differences in both performance and side effects such as poor sleep and anxiety to genetics, with habitual intake playing a role too (Guest et al., 2021), and the FDA lists jitters, anxiety and an upset stomach among the signs of too much (FDA). Race morning is the wrong time for your first double espresso or your first caffeinated gel, so try your race-day dose before a long run first.

Fluids before the start

Start the race hydrated, not waterlogged. The position statement recommends 5 to 10 milliliters of fluid per kilogram of body weight in the 2 to 4 hours before exercise, aiming for pale yellow urine (Thomas et al., 2016). For a 160-pound runner that’s about 360 to 730 milliliters, or roughly 12 to 25 ounces, spread across the morning rather than downed in the start corral.

More isn’t better. An international consensus panel on exercise-associated hyponatremia, the dangerous drop in blood sodium that comes from drinking more than you lose, recommends drinking when you’re thirsty, and one large study it cited found symptomatic cases in 1 percent of athletes in endurance events (Hew-Butler et al., 2015). The marathon race week guide covers the same risk over a longer race.

What to eat during the race

What you take on the course depends on your finish time as much as your breakfast does. For events of 1 to 2.5 hours, the position statement recommends 30 to 60 grams of carbohydrate per hour (Thomas et al., 2016). Jeukendrup’s own guidance is that about 30 grams per hour is probably enough for 1 to 2 hours, and that hard efforts of 45 to 75 minutes benefit from small amounts or even a carbohydrate mouth rinse (Jeukendrup).

Standard GU gels carry 21 to 23 grams of carbohydrate (GU Energy), so 30 grams an hour is about one gel every 45 minutes and 60 grams is closer to one every 20 to 25 minutes. A 6 percent sports drink, the standard strength Sports Dietitians Australia describe for aid stations (Sports Dietitians Australia), works out to about 14 grams in an 8-ounce cup. At 30 grams an hour, a runner finishing near 90 minutes needs about two gels or the sports-drink equivalent, while a 2:15 finisher needs three at the low end of the range and six at the top.

Whatever you use, practice it. The gut adapts to taking in carbohydrate while you run, and Jeukendrup suggests rehearsing your race fueling at least once a week, with tolerance likely improving within 6 to 10 weeks (Jeukendrup, 2018). The long run is where that happens, and the 18-week half marathon plan gives you a long run every weekend to rehearse breakfast, coffee and gel timing before race day. The half marathon training guide covers how the rest of the build fits around it.

FAQ

Should I carb load for a half marathon?

If you expect to finish in more than about 90 minutes, yes. Aim for 10 to 12 grams of carbohydrate per kilogram of body weight per day for the 36 to 48 hours before the race. If you’ll finish faster, a normal carbohydrate-rich day of 7 to 12 grams per kilogram is enough (Thomas et al., 2016).

What should I eat the morning of a half marathon?

Something familiar, high in carbohydrate and low in fat, fiber and protein, eaten 1 to 4 hours before the start at 1 to 4 grams of carbohydrate per kilogram, with the smaller amount when you eat closer to the gun. Toast with peanut butter, crumpets with banana and honey, porridge and a banana smoothie are all on Sports Dietitians Australia’s list (Sports Dietitians Australia).

How long before a half marathon should I eat?

One to four hours. A small breakfast of about 1 gram per kilogram works an hour or two out, and a full meal fits 3 to 4 hours before a later start. With a 7 a.m. start, that usually means a light breakfast around 5 or 5:30.

Should I drink coffee before a half marathon?

If you already drink coffee and it sits well before long runs, yes. Caffeine improves endurance performance at 3 to 6 milligrams per kilogram, usually taken about an hour before (Guest et al., 2021). Test your exact dose in training first.

How many gels do I need for a half marathon?

It depends on your finish time. At 30 to 60 grams of carbohydrate per hour and about 22 grams per gel, a 2-hour runner needs roughly three gels at the low end and five or six at the top, and fewer if you’re also drinking sports drink on the course. Runners finishing close to 90 minutes need less.

Is pasta the night before a half marathon a good idea?

As one meal among several, yes. The carbohydrate for a full load is spread across the day or two before, so the pasta dinner is part of it rather than the whole thing. Keep the sauce simple and go easy on cream and cheese.

Should I change what I eat during the taper?

The last few days, yes. Carbohydrate loading works by pairing a carbohydrate-rich diet with a drop in training (Thomas et al., 2016), so the load lines up with the end of your half marathon taper.