The food you eat the day before a race won't make you faster. The food you eat in the 12 hours before a race can absolutely make you slower, especially if you get it wrong. Race nutrition is mostly about avoiding mistakes: don't bonk, don't get a stitch, don't end up needing a toilet at kilometre five.

This is the beginner's guide to fuelling the night before and morning of any race from a parkrun to a marathon. We'll cover what to eat, when to eat it, what to avoid, and how the rules change with race distance.

The Night Before: Carb Up Without Going Mad

The classic image is a giant plate of pasta the night before a marathon. That's roughly the right idea but most people overdo it. The body can only store a limited amount of glycogen (the storage form of carbohydrate), and once those stores are full, eating more just sits in your stomach and digestive system overnight.

For races up to 5K and 10K, a normal carb-rich dinner is plenty. Pasta with a tomato-based sauce, rice with grilled chicken, anything you'd normally eat after a long training session. No special preparation needed.

For races 10 miles and longer, lift the carb portion of the dinner by about 25 to 50 per cent compared to your usual. Add an extra portion of rice, an extra slice of bread, a piece of fruit. Keep the protein normal and cut back slightly on fat and fibre, both of which sit heavy.

What to Avoid the Night Before

• Anything spicy. Even if you eat curry weekly, race day is not the day to test the system.
• Heavy fibre. Big bowls of beans, large salads, lots of broccoli. Fibre is great for life, terrible for race day mornings.
• Alcohol. Even one glass of wine measurably reduces sleep quality and dehydrates you. Save it for the finish line.
• Anything new. The week of a race is the worst possible time to try a new restaurant, a new cuisine, or a fancy ingredient. Stick to what your body knows.

The Morning Of: 3 Hours, 90 Grams, Boring Food

The aim of the race-morning meal is to top up your liver glycogen (which depletes overnight) without sitting in your stomach when the gun goes off.

The proven formula:

• Eat 3 hours before the start. Hard rule. Less than 2 hours and the food is still digesting. More than 4 hours and you're going to be hungry before you even start.
• Aim for 60 to 90g of carbs. For a 70 kg person that's about 1g per kg of bodyweight. Slightly more for marathons.
• Keep protein moderate, fat and fibre low. 10 to 20g of protein is fine. Keep fat under 15g and fibre under 5g.
• Drink 400 to 600 ml of water with it. Sip, don't gulp. Stop drinking large volumes 90 minutes before the start.

The Tried and Tested Race Breakfasts

The boring options that have got more runners across the line than anything else:

• Porridge with banana and honey, plus black coffee or tea
• 2 slices of white toast with jam or honey, plus a banana
• Bagel with peanut butter and jam (smaller portion of PB)
• White rice with a small omelette (works for some, not for everyone)
• Pancakes with maple syrup and a banana

The common ingredient: refined carbs (white bread, white rice, oats), simple sugars on top (honey, jam, syrup), low fibre, low fat. Boring. Effective.

The Three Mistakes Every Beginner Makes

The Bottom Line

Race nutrition is the night before, the morning of, and absolutely nothing you haven't tested in training. Carb-up dinner, no fancy. Breakfast 3 hours before the gun, 60 to 90g of refined carbs. Drink to thirst, not to plan. Avoid anything new, anything spicy, anything fibrous, anything different.

Get those simple rules right and race day starts the way it should: settled, fuelled, and ready to focus on the running rather than what your stomach is doing.