How to Fuel a Marathon

Whether you’re training for your first marathon or looking to improve on a previous performance, one thing is clear: a well-practised fuelling and hydration plan is essential if you want to perform at your best and steer clear of common nutrition pitfalls.

Training for a marathon places a high demand on your body’s energy systems. The most common issues runners face include dehydration, running low on fuel, cramping, gut distress, and even overhydration. The good news is, with a little planning and regular practice, most of these problems can be avoided.

Fuelling Your Training Runs

Your long training runs are the ideal time to rehearse your nutrition strategy. Use them to trial different foods, drinks, timings and quantities. Everyone’s gut is different, and what works well for one runner might not suit another — so experiment early and find out what works for you.

Carbohydrates are your primary fuel source during endurance exercise, delivering energy to your muscles quickly and efficiently. However, your body can only store around 500g of carbohydrate as glycogen — enough for approximately 90–120 minutes of running — which means you’ll need to top up during the race to avoid hitting the wall.

Many runners prefer training early in the morning, particularly on weekends. If you’re running long first thing, focus on eating plenty of carbohydrate-rich foods the day before. This will ensure your glycogen stores are well stocked. You can skip a full breakfast if you prefer, but do try to eat a small pre-run snack 15–30 minutes beforehand — something like a banana, a slice of toast with honey, or half a bagel with peanut butter can work well.

If eating solid food feels uncomfortable that early, opt for a liquid source of fuel such as a sports drink, diluted fruit juice or a smoothie. These will provide quick-acting carbohydrates and fluid to help maintain your energy and hydration levels.

Practise Your Strategy

Aim to simulate race-day conditions during at least two or three of your long training runs. Use the same types of fuel, taken at the same intervals and quantities you plan to use on race day. This will help build confidence and minimise surprises on the big day.

Also practise drinking while running — from both cups and bottles, if possible — as it can take a bit of getting used to. Start with small sips and build up gradually. If you plan to use the drinks provided by the race organisers, check in advance what will be available and practise with them during training.

Start fuelling about 45–60 minutes into your long run. How much carbohydrate you need depends on your expected finish time:

• > 4 hours: Aim for ~30g carbs/hour

• 3–4 hours: ~60g carbs/hour

• < 3 hours: Up to 90g carbs/hour (ideally from multiple carb sources like glucose + fructose)

Some examples of 30g carbohydrate portions include:

• 1 large banana

• 500ml isotonic sports drink

• 1 cereal or fruit + nut bar (check label for carb content)

• 2 Medjool dates

• 1 energy gel (check the label for carb content)

2–3 Days Before the Race: Carb-Load

In the final days before the marathon, you’ll want to arrive at the start line with fully stocked glycogen stores. This is where carbohydrate loading comes in.

Begin reducing your training volume — known as tapering — in the 2–3 weeks leading up to the race. During the final 2–3 days, increase your intake of high-carb foods like pasta, rice, oats, potatoes and sweet potatoes. Shift your plate so that carbs make up a larger portion of your meals, while slightly reducing fat and protein to make room.

Be mindful not to overeat — carb-loading is about increasing the proportion of carbs in your diet, not the total quantity of food. Eating too much can lead to bloating, digestive upset and sluggishness. If you’re prone to gut issues, consider lowering your fibre intake in the 48 hours before the race to reduce the risk of GI distress.

The Day Before the Race

Plan your main meal for lunchtime rather than late in the evening — this gives your body plenty of time to digest, so you don’t wake up feeling heavy or bloated. A simple, carb-rich meal with a moderate amount of protein and low fat is ideal. For example:

• Pasta with tomato sauce and chicken

• Rice with tofu or beans

• Jacket potato with hummus or tuna

Avoid trying anything new or unfamiliar — race eve isn’t the time to test a spicy curry or that trendy high-fibre energy bar.

Race Morning

Your pre-race meal should be eaten 2–4 hours before the start to give your body time to digest and absorb nutrients. This meal is all about topping up liver glycogen and helping you start the race well-fuelled.

Stick to familiar, carb-rich foods that you know sit well. Good options include:

• Porridge or overnight oats with banana or honey

• Granola with yogurt and berries

• Toast or bagel with jam or nut butter

Hydration is also key. Aim to drink around 5–10 ml of fluid per kilogram of body weight in the 2–4 hours before the start. Check your urine colour — it should be pale yellow. After that, sip as needed, but avoid overdrinking.

15–30 Minutes Before the Start

If you skipped breakfast or still feel hungry close to the start, taking in a small dose of carbohydrates can help provide an energy boost for the early miles. Aim for 20–30g of carbs with some fluid. Options include:

• A banana

• A gel

• Half an energy bar

• A small bottle of sports drink

This is optional — if you don’t feel like it, don’t force it.

During the Race

Follow the fuelling and hydration plan you’ve practised in training. Stick with products you know work for you and avoid trying anything new on the day — even if it’s being handed out on course.

Be ready to adapt your strategy if conditions change. On a hot day, you may need to drink more; if you start to feel nauseous or bloated, you might need to ease off the carbs for a short period.

Keep in mind:

• Aim for 30–90g of carbs per hour, depending on your finish time.

• Hydrate according to thirst and sweat rate — somewhere between 400–800ml fluid/hour is typical for most runners.

After the Race

Recovery starts as soon as you cross the finish line. Begin by rehydrating — water, electrolyte drinks or a recovery formula can all help replace lost fluids.

Next, focus on food. Aim to eat a recovery meal or snack within 60–90 minutes containing both carbohydrate and protein to replenish glycogen and support muscle repair. Include some colourful fruit or vegetables to help reduce inflammation and oxidative stress.

Great post-race options include:

• A smoothie made with milk, fruit and protein powder

• Yogurt with granola and berries

• Rice with chicken and vegetables

• A veggie omelette with toast or potatoes

After that? You’ve earned a treat — so enjoy whatever you fancy!

Final Thoughts

Your marathon nutrition plan should be just as personalised as your training programme. Practise early and often, pay attention to how your body responds, and trust your plan on race day.

Key Takeaways:

• Carb-load smartly and taper your training

• Practise your fuelling strategy on long runs

• Stick to familiar foods and drinks on race day

• Hydrate according to thirst and conditions

• Refuel with carbs and protein after the race