One of the often overlooked reasons runners struggle mentally during a marathon or ultra is simply lack of nutrition. It’s not only your muscles that suffer when you run low on fuel — your brain does too. The brain relies heavily on glucose for energy, and when your blood sugar drops too low (a condition known as hypoglycemia), it can have a major impact on your mood, decision-making, and mental resilience. Feelings of overwhelming negativity, fear, and anxiety late in a race are often not just about mental toughness — they can be real physiological signs that your brain is running on empty.

Research shows that even mild hypoglycemia can impair cognitive function and mood, leading to poor decision-making, lack of motivation, and an increased perception of effort. In simple terms, everything feels harder, more painful, and more overwhelming when you’re under-fueled. Negative self-talk, panic, and the sense that you can’t go on, can hit hard when your brain isn’t getting the fuel it needs to function properly.

This is why having a structured race-day nutrition plan is just as important as your physical training. Taking in calories regularly — through gels, sports drinks, or real food — helps maintain stable blood glucose levels, keeping both your body and your mind performing at their best. Recognising when negative thoughts are actually a sign of low energy rather than a true reflection of your ability can be a game changer. Fuel your brain as well as your body, and you’ll put yourself in the best position to finish strong, both physically and mentally.

Marathon Nutrition Guidelines: Fuel Smart, Finish Strong

These are general guidelines for road marathons, but remember, your exact needs depend on factors like your body size, pace, and experience. When in doubt, bring more fuel than you think you’ll need. It’s far better to carry an extra gel than to run out when you need it most.

How Much Fuel Do You Need?

If you’re running up to 4 hours:
Aim for 35–60 grams of carbohydrates per hour

  • Faster runners and those with larger builds may need up to 90g/hour

If you’re running 4–5+ hours:
Aim for 45–60 grams of carbohydrates per hour

  • This helps delay fatigue and keeps your brain functioning optimally

How to Take It

Start fueling within the first 30 minutes of your race (around the 5km mark), and continue to consume carbohydrates every 30–40 minutes. Don’t wait until you feel tired — by then it’s often too late.

Most common options on race day:

  • Gels, chews, sports drinks, or bars (easiest to carry and absorb)
  • Real food like white bread sandwiches, bananas, or dates — but only if you’ve practiced this in training

👉 Pro tip: Plan to take a gel about 1km before an aid station so you can wash it down with water.
Carbohydrates are best absorbed in about a 10% solution, so aim to dilute 25g of carbs (from a gel) with roughly 250ml of water. You don’t need to drink it all at once — small sips at each aid station work well.

If you’re aiming for 50g carbs/hour, make sure you’re getting at least 500ml of water per hour to support digestion.

Hydration and Electrolytes

General hydration guideline:
500ml–1L per hour, depending on your sweat rate, temperature, and conditions.

If you’re a heavy sweater or prone to cramping, consider electrolyte tablets or salt capsules. Some sports drinks and gels include electrolytes, and most races offer electrolyte options at aid stations. Use them!

Why Race-Day Breakfast Matters

Your brain and muscles rely on stored carbohydrates (glycogen), but overnight those stores get partially depleted. Skipping breakfast means you’ll start the race under-fuelled, increasing your risk of early fatigue, poor pacing, and mental fatigue — even if you’ve carb-loaded beforehand.

A well-timed, high-carb, low-fibre breakfast 2–3 hours before your start time tops up your glycogen stores and stabilises blood sugar. Good options include:

  • Toast with honey or jam
  • Rice or oats with banana
  • White bagel with peanut butter

Pair it with 300–600ml of fluid and aim for 1–2g of carbs per kg of body weight.

👉 Make sure you practice your exact race day breakfast on some of your long training runs.

Day-Before Long Run or Race Day Fueling

Start preparing 1–2 days in advance:

  • Hydrate well: 2+ litres/day, plus an electrolyte drink or added salt to meals
  • Focus on carbs: Include easy-to-digest carbs like fruit, rice, potatoes, pasta, and bread
  • Dial back fibre, fat, and protein to avoid gut issues and maximise carb storage
    This will help fully load your glycogen stores and reduce the risk of hitting the wall.

Individualised Nutrition Advice:  If you would like some help planning your race day fuel, or help with general nutrition leading up to the day, contact Tamara Madden from Mad On Nutrition – you can book an appointment via the website.

🏁 Race Week Fuelling Checklist

Print this fuelling checklist and stick it on the fridge on race week and start ticking the boxes. Runners love to tick boxes, plus nailing your nutrition will help you nail your race.

PRINT ME – Race Day Fuelling Checklist – PRINT ME