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How to Fuel for Race Day: What to Eat Before, During & After a Run

05 September 25

From pre-race brekkie to mid-run gels and recovery meals, here’s how to fuel like a pro

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During the race, your hydration needs will depend on factors like temperature, how much you sweat, and how long you're running.

With your next race just around the corner, it's not just your legs that need to be race-ready – what you eat and drink matters too.

Whether you're chasing a PB or just hoping to make it to the finish line in one piece, fuelling your body the right way can make all the difference.

A running race is no small feat. It's high-impact, high-effort, and high-stakes for your energy reserves. But with the right nutrition, you can show up at the start line feeling strong – and finish with a smile (or at least not a grimace).

To help you navigate what to eat, sip, or skip before, during, and after the race, we caught up with Accredited Sports Dietitian, Personal Trainer, and Owner of 98 Gym (Canberra), Harriet Walker. From carb-loading myths to mid-run gels and post-race recovery tips, here's everything you need to know to fuel like a pro.

What should you eat the day before and morning of a running race?

The good news is you don't need to go full carb-load mode for this distance – but according to Harriet, it's still important to focus on fuelling well the day before.

"Emphasise carbohydrate-rich meals to top up glycogen stores," she says. Think pasta, rice, potatoes, fruit, and bread, and aim to include carbs at each meal. "Stick to familiar, low-fibre, easily digestible foods to avoid any gut issues," she adds.

For dinner the night before, Harriet recommends keeping things moderate – nothing too heavy or spicy. A balanced meal with carbs and a little lean protein is ideal, like pasta with lean mince or rice with grilled chicken.

Come race morning, Harriet says to eat 2-3 hours before the start. She points out that this meal is less about replenishing energy and more about keeping your blood glucose levels steady, which supports concentration, coordination, and stamina.

"What and how much you eat is individual, but choose something high in carbs, low in fibre, and easy to digest – like toast with jam and banana, or oats with honey and milk," says Harriet. She also suggests practising early eating in the lead-up so your body gets used to it.

Not a fan of early breakfasts? No stress. "A small snack or liquid carb option closer to the start can help top up energy," she says. She recommends options such as a banana, a slice of white toast with honey, a fruit pouch, dried fruit, or a sports drink with 30-40 grams of carbs. "These are all quick to digest and give your body the final boost it needs within 30-60 minutes of go time."

What's the best way to manage hydration on race day – from the night before to the finish line?

We all know staying hydrated is important, but when race day rolls around, it's not just about chugging water at the start line. According to Harriet, proper hydration should begin well in advance.

"Start 24 hours before the race and drink water consistently throughout the day," she instructs. "Aim for pale yellow urine as a rough guide."

"In the final 2-4 hours before the race, consume 5-10 mL per kilogram of body weight. Including electrolytes during this window can help your body retain fluid and improve hydration status – especially if you're a heavy or ‘salty' sweater (IYKYK)."

During the race, your hydration needs will depend on factors like temperature, how much you sweat, and how long you're running. "For most runners, 400-800 mL per hour is sufficient," says Harriet. "But avoid overhydrating, which can lead to hyponatremia (low blood sodium)."

For shorter races like the City2Surf, plain water usually does the trick. "Electrolyte drinks during the race might not replace significant sweat losses in a 14km event, but the sweetness can give you a perceived energy boost and help reduce fatigue," she explains. "Still, water is your most efficient choice."

And once you've crossed the finish line? Time to replenish. "Aim to replace 125-150% of the fluid you've lost with sodium-rich fluids or simply salt your food to speed up recovery," Harriet advises. "Weighing yourself before and after the race can help estimate sweat losses."

How do running gels work, and when's the best time to take them?

"Running gels are concentrated carbohydrate sources, typically providing 20-30 grams of simple sugars (like glucose and fructose) per packet," says Harriet.

As Harriet explains, they're designed for rapid digestion and absorption during prolonged endurance efforts, helping to maintain blood glucose and delay fatigue.

So, how long do you need to be running to "earn" the sweet reward of a gel? Harriet explains that they're most useful in events lasting over 60-75 minutes.

"For optimal effect, take one 10-15 minutes before the race start (especially if breakfast was early) and then every 30-45 minutes during the race, depending on your carb target (30-60 grams/hour for most)," she says.

Harriet also explains that it's important to always take gels with water to support absorption and reduce the risk of GI distress. "Never try a gel for the first time on race day – practice during training," she says.

Do you really need to fuel differently for a 5K vs. a marathon?

Ever wondered if you need to fuel differently for a 5K compared to a marathon? You're not the only one. "As race distance increases, the body's fuel and hydration demands rise accordingly," explains Harriet.

"Longer races require more structured fuelling to maintain energy availability, whereas shorter events can often be completed using pre-race glycogen stores alone."

Harriet's tips for adjusting your race-day nutrition by distance:

5K: No need for mid-race fuelling. Eat a light, carb-based pre-race meal 2-3 hours prior. A small carb snack or coffee 30-60 minutes before can boost alertness.
14K (City2Surf): A mid-race gel may help some runners. Hydration depends on the weather; sipping water or electrolytes is usually enough.
Half Marathon: Carb-load the day before. Eat a familiar, carb-rich breakfast. Use a gel before the start and another around halfway. Hydrate every 20-30 minutes if it's warm.
Marathon: More planning, preparation and practice required to fuel strategically. Carb-load for 2-3 days before. Take 2-3 gels per hour (up to 90 grams carbs/hr if a well-trained athlete). Hydrate with electrolytes to reduce risk of cramps or hyponatremia.

Do runners really need electrolytes, or is water enough?

"Electrolytes help regulate fluid balance, nerve signals, and muscle contractions," says Harriet. "Sodium is the most important during long runs due to sweat loss, and replacing sodium during races over 90 minutes supports performance and reduces cramp risk."

That said, for shorter events, intra-race electrolyte intake isn't as critical. "For shorter distances/duration races like City2Surf, day-to-day nutrition and pre/post-race strategies should be the focus over intra-race nutrition," she explains.

While potassium, magnesium, and calcium play an important role, Harriet says sodium is the top priority – especially in hot conditions or if you're a heavy or salty sweater. "In those cases, electrolyte drinks or tablets can be essential," she adds.

What should post-race nutrition look like for optimal recovery? Is the 30-minute "anabolic window" real?

You've crossed the finish line – now what? It might be tempting to dive straight into celebration mode but giving your body the right fuel after the race can really pay off in terms of recovery.

While the much-hyped "30-minute anabolic window" gets a lot of attention, Harriet explains it's more relevant to resistance training than endurance events like running. "Even then, the window is more like 2-3 hours," she says. For runners, the focus post-race should be on replenishing glycogen, rehydrating, and providing enough protein to repair muscle tissue between training sessions, she says.

So when should you eat? "Aim to refuel within 60 minutes of finishing," Harriet advises. "The 30-minute window isn't critical, but eating sooner can support better recovery outcomes." She recommends prioritising carbs – about 1-1.2 grams per kilogram of body weight – to refill glycogen stores, plus 20-30 grams of protein to support muscle repair.

Sodium also plays a key role in speeding up rehydration and recovery, so reaching for salty snacks or a sports drink can help replenish what you've lost.

Great post-race options include recovery smoothies, chocolate milk with a sandwich, or a meal like rice with chicken and veggies. The goal is to choose real, easy-to-digest food, especially after a big effort.

What are some common mistakes runners make with race-day nutrition and hydration?

There are a few common missteps that can derail your run:

Trying new foods, drinks, or gels on race day: This often causes gastrointestinal (GI) issues.
Eating high-fibre, high-fat, or high-protein meals before the race: These can lead to stomach discomfort.
Under-fuelling the day before or skipping breakfast: Both can limit your energy and performance.
Drinking too much plain water without electrolytes: This may cause electrolyte imbalances.
Not adjusting hydration for hot or humid conditions: Your needs can change significantly with the weather.
Relying solely on thirst to guide hydration: This can result in under-hydration during the race.

How can runners with sensitive stomachs or GI issues adjust their race-day nutrition plan?

Let's talk about the not-so-glamorous side of running: gut issues. If you've ever found yourself sprinting toward a porta-loo instead of the finish line, you're not alone. GI distress is common, especially during high-impact races, and it can be triggered by a mix of mechanical, physiological, and dietary stress, says Harriet.

"The repetitive motion of running can jostle the digestive tract – particularly the lower GI – leading to urgency or discomfort," she says.

"Blood flow is also redirected away from the gut to working muscles, which reduces digestion and increases the risk of cramping."

We found out that certain foods, especially those high in fibre, fat, or poorly tolerated carbs like FODMAPs, can ferment or draw water into the bowel, making symptoms worse. On top of that, dehydration, overhydration, or pre-race nerves can crank up the discomfort even more.

The good news? There are ways to train your gut (or at least build up tolerance), just like your legs. But as Harriet explains, everyone's approach will be different depending on their personal triggers.

Some starting points Harriet suggests are:

Choose low-fibre, low-fat meals the night before and morning of the race
Avoid high FODMAP foods like onions, apples, and legumes
Space meals out – eat 2.5-3 hours before the race, and a light snack an hour before if needed
Test different gels and drinks during training to see what works for you
Use liquids or soft-texture fuels like baby food if solids are hard to tolerate
Drink fluids steadily, not in large volumes at once
Manage nerves by practising your race routine to reduce gut symptoms.