How to Fuel for Race Day: From the 5K to the Ultramarathon

How much you need to eat and drink during a race depends almost entirely on how far you're going and how fast. On a 5K you can basically ignore fueling, but by the marathon it's part of the race, and in an ultra it can decide whether you finish at all. Here's how to fuel for each one.

Race-day fueling at a glance

The 5K

The 5K is one of the shortest and most popular race distances around. Most recreational runners finish in about 30 to 40 minutes, while faster, well-trained amateurs can dip under 20. That's just not long enough to need fueling. As long as you had a proper meal a couple of hours before, you can get through a race this short on the fuel you already have on board.

Water is more of a personal call. Fast runners and pros often skip it entirely, since stopping to drink can break their rhythm and cost them time. If you're running slower than about 8:00 min/mile (5:00 min/km) and not chasing a specific time, drink whenever you feel like it. For a 5K, plain water is plenty, since the distance is too short to worry about electrolyte loss.

After you finish, just eat normally. The effort is short enough that your body isn't under much stress and doesn't need special recovery supplements. If you ran hard or kicked hard at the finish, you might have a serving of protein afterward to help your muscles recover.

The basics for a 5K:

• Take a few sips of water before the start.
• Skip the food, you don't need it, and drink only if you feel like it, even on a hot day.
• Add a serving of protein or amino acids afterward to speed muscle recovery, especially after a hard effort.

The 10K

Like the 5K, a 10K really doesn't require fueling. The effort still isn't long enough, and a healthy body can handle it on its own reserves. If a 10K takes you well over an hour, you could grab something at an aid station, like a banana, but there's no need to fuss over gels or a fueling plan.

Drinking is another matter, especially in the heat. Pros and fast amateurs usually get through a 10K without water, but they're only out there for 30 to 40 minutes. If you're trained and used to running without water, you can probably manage the race without it too. But if you start feeling thirsty, particularly on a hot day, don't skip the aid stations.

After the race, put a little more thought into recovery. A sports drink works well here, but sip it slowly instead of gulping it down, so you don't overload your stomach. Later in the day, add some protein or amino acids to help your muscles.

The basics for a 10K:

• Drink about 7 oz (200 ml) of water or a sports drink half an hour before the start.
• Skip the fuel during the race, a trained body doesn't need it, but grab a banana at an aid station if you'll be out there well over an hour.
• Drink to thirst, and don't skip the aid stations when it's hot.
• Refuel afterward with water or a sports drink for your fluids and electrolytes, plus a serving of protein.

The Half Marathon

The half is the first distance where fueling really enters the picture, and here's why.

Your body stores enough glycogen, its fast-access carb fuel, for roughly 90 minutes of running. Once you pass that mark, those stores run low and your body leans more on fat, which is usually when your legs start to feel heavy and your pace fades. A 5K or 10K is over well before that point, but a half often isn't, so whether you need to fuel comes down to how long you'll be out there.

That makes it mostly a question of pace. The average half-marathoner in the US finishes somewhere around 2:00 to 2:15, well past the 90-minute mark, so most recreational runners do better with some carbs along the way.

Faster runners finishing under about 1:40 can often skip the gels and get through on water alone, especially if they train that way. If you're somewhere in between, or you know you tend to fade late in a race, it's better to plan on fueling.

If you're fueling, here's a realistic plan:

• Drink about 7 to 10 oz (200–300 ml) of water or a sports drink half an hour before the start, take a few more sips just before the gun, then drink to thirst at the aid stations rather than forcing fluids at every one.
• Aim for about 45 to 60 g of carbs per hour, which usually works out to a gel every 30 to 40 minutes, or three to four across a typical half.
• Take your first gel early, around 20 to 30 minutes after the start, before you actually feel low, then hold that rhythm. If you'd rather go by distance, that's roughly every 3 miles (5 km).
• Wash gels down with a little water, even the "no water needed" ones, which go down easier and taste less cloying that way.
• Save any caffeinated gels for the second half, as a boost.
• Refuel afterward with carbs and electrolytes, plus some protein to help your muscles recover.

The Marathon

There was a time when the sports-nutrition industry didn't exist and people ran marathons on nothing, maybe a banana somewhere near the end. Things have changed. And given the option, it's fair to say fueling a marathon is definitely the way to go.

The plan looks a lot like the half, just more of it, since you're out there far longer:

• Drink about 7 to 10 oz (200–300 ml) of water or a sports drink half an hour before the start, then a few more sips just before the gun. During the race, drink regularly and roughly to thirst, rather than forcing fluids at every single station.
• Aim for at least 60 g of carbs per hour (many runners handle more). In practice that's a gel every 30 to 40 minutes, starting around 30 minutes in, which can add up to five to eight gels over a marathon depending on your pace and what else you're taking in. If 60 g feels like a lot for your stomach, practice it on your long runs to train your gut to absorb more.
• Alternate your gels with the real food at aid stations, like bananas or orange slices, anything that doesn't take much chewing. A marathon is a long day out, and gels alone can wear on your stomach.
• Take your gels with water rather than with a sports drink. Doubling up on sugar all at once is a common cause of stomach trouble, so keep the sports drink as a separate sip.
• Save caffeinated gels for the later miles as a lift, and don't overdo them. Somewhere around 100 to 300 mg of caffeine total is plenty for most runners.
• Refuel afterward with carbs and electrolytes, then some protein later on, either whey or amino acids. There's no rush, since research has walked back the old "anabolic window" idea that you had to get protein and carbs in within a couple of hours of finishing (Aragon & Schoenfeld, 2013).

The Ultramarathon

An ultramarathon is any distance beyond the marathon, whether that's a 50K (31 miles) or a 100-miler. So, the fueling varies enormously from one race to the next.

Still, a few principles hold across all of them, and the biggest one is to practice everything in training, since stomach trouble, not tired legs, is the most common reason people quit long ultras.

• Start with about 7 to 10 oz (200–300 ml) of a sports drink half an hour before the gun.
• Aim for about 60 to 90 g of carbs per hour, from a mix of gels, chews, drink mix, and real food. That's more than a marathon, and hitting it comfortably takes a trained gut, so build up to it in training rather than on race day. Products that blend glucose and fructose tend to absorb better and sit easier at those amounts.
• Start fueling early and keep it steady. The longer the race, the more consistent you should be.
• Lean more on real food as the hours add up. You can't run for 24 hours on gels alone, so eat what the aid stations offer, and mix in variety to fight flavor fatigue.
• Bring a few of your own fast carbs in "regular" form, like dates, gummies, or rice cakes. They can save you if an aid station runs out or you just need a lift.
• Drink to thirst rather than on a schedule, using an electrolyte drink to cover some of your sodium. Salt needs vary a lot between runners, so lean on salty foods and drinks, and add salt tabs or capsules mainly if you're a heavy or salty sweater, or it's hot.
• Refuel gently at the finish. Your stomach is shocked, so start with easy-to-digest foods in small portions, focusing on easy carbs and fluids with electrolytes, plus some protein.

Common race-day mistakes

A few fueling errors trip up runners again and again. Most are easy to avoid once you know them:

1. Don't try anything new on race day. Test every gel, energy bar, drink, and food in training first, and at aid stations stick to what you know. If you're unsure about the organizer's sports drink or an unfamiliar energy bar, go with water and a banana.
2. Don't start to fuel too late. By the time you feel low on energy, you're already behind, so take your first gel in the first half hour, before you need it.
3. Don't overdrink. Too much fluid is more dangerous than mild thirst and can cause hyponatremia, or dangerously low sodium, so drink to thirst instead of forcing it at every station.
4. Don't ignore the weather. Heat means more sweat, so you'll usually want more fluid and more sodium on a hot day, and a little less when it's cool. Adjust on the run rather than sticking rigidly to a plan.
5. Don't overdo caffeine. A little helps late in a race, but too much can upset your stomach or leave you jittery. Around 100 to 300 mg total is plenty.
6. Don't take gels with a sports drink. Together they double up the sugar hitting your gut at once, a common cause of stomach trouble, so use plain water instead.

Do you need to fuel every workout?

Finally, do you need to follow these plans for every training run? No, you don't.

For workouts (and races) under about 90 minutes, especially at easy to moderate intensity, fuel isn't necessary. A healthy body can cover it from its own reserves.

Now and then it's actually useful to step outside your comfort zone and do a long run without any fuel. This creates a controlled kind of stress that may teach your body to use fat a bit more effectively.

There's another reason to practice this. Things go wrong in races: aid stations run out, gels get dropped or forgotten, and so on. You should be ready for that, physically and mentally.

At the same time, you do need to "rehearse" your race fuel. The best place is a long run with some miles at race pace, using exactly what you plan to use on the day. This also trains your gut to absorb carbs more comfortably, which cuts the risk of stomach trouble on race day. Before a marathon, your longer runs of around 19 to 22 miles (30–35 km) are ideal for dialing it in.

One more thing. Sports nutrition isn't the same as everyday healthy eating. Check the label on a "healthy" protein or energy bar. In fat and calories, plenty of them are right up there with a candy bar. So, regularly loading up on these "treats" can quietly add weight over time.

The bottom line

Fueling during a race matters, but not at every distance.

You can run a 5K or 10K on nothing more than a good breakfast eaten 2 to 3 hours before the start. Drinking is optional for a 5K and a bit more useful for a 10K, depending on your pace and the weather.

A half marathon can go either way. If you're finishing around 90 minutes (or a little more), you can manage without gels. But most runners are out there closer to two hours or beyond, which is long enough that skipping fuel usually catches up with you late in the race. If that's you, start fueling in the first half hour so your energy doesn't drain before the finish, and drink to thirst along the way.

You can't run a marathon or an ultra without fuel. The longer the distance and the more hours on your feet, the more you'll need to alternate gels with real food.

Fueling is a very individual thing. So, experiment to find what works for you, and settle on the routine that keeps your stomach happy along the way.

Frequently asked questions

Do I need gels for a half marathon?

If you're finishing under about 1:40, you can usually get by on water alone. Most runners finishing around two hours or more do better taking in some carbs, roughly 45 to 60 g per hour.

How many gels do I need for a marathon?

Plan on at least 60 g of carbs per hour, which usually works out to five to eight gels over the race, depending on your pace and what else you eat along the way.

Water or sports drink?

Either works. Water is fine if you're getting carbs and electrolytes from gels and food, while a sports drink adds some of both, which helps on longer efforts. Just don't take a gel and a sugary sports drink at the same moment.

Should I fuel differently in the heat?

Yes. You sweat more when it's hot, so you'll generally need more fluid and more sodium. Drink to thirst and lean on salty foods or electrolyte drinks.

This article is for general guidance only. Talk to a qualified professional before taking any supplements or medications.