How to nail your marathon week nutrition and avoid ‘bonking’
It can be confusing knowing what to eat and drink on the week building up to a marathon, how much carbohydrates should you eat? how much water do you need to drink? do you need to avoid protein and fiber? - especially if it’s your first time round. After reading this guide you will know exactly where to begin and you’ll be best equipped to smash your marathon and avoid the infamous ‘bonk’. For a quick summary you can screenshot and use, scroll to the bottom of this article!
Why do we carbohydrate load?
Carbohydrates are a fundamental source of fuel for your body when you exercise. During exercise, our body’s will utilise carbohydrates and fats to produce energy. Higher intensity exercise uses up more carbohydrates, while less intense activity uses up more fats. Carbohydrate loading is a nutritional strategy used to help improve physical performance. It is a strategy commonly used by competitive and everyday athletes which involves adjusting your diet and activity levels to boost the amount of carbs in your body in the run up to an event.
Should I drink beet juice?
Although we’re keeping things relatively the same from Monday - Wednesday of race week, you can supplement this drink that has been found to aid marathon performance. Beetroot juice. Now before I go into the benefits and why you should implement beetroot juice I must warn you, do not try anything new on race week, make sure you have tried and tested this at least a few weeks prior (I’d recommend trying it out on your highest volume training week).
So why should you supplement beet juice? The main benefit of beetroot juice (specifically beetroot shots) is that it enhances blood flow which consequently enables greater oxygen delivery to your working muscles leading to enhanced running performance, endurance and reduces fatigue; this is due to the high nitrate content of beetroot which is turned into nitric oxide in the body, nitric oxide then relaxes and widens blood vessels, allowing for the greater flow of blood.
Now, how should you take beetroot juice during race week? You’ll want to steer clear of standard beetroot juice from the carton as it is rich in fiber (which too much of can cause gut issues) and instead take beet shots which have been filtered down to remove the high fiber content. Aim for 350mg-500mg at least one hour before exercise and for 7 days leading up to the marathon.
How do you carb load?
I’ll start off by keeping it simple and assuming your marathon is being held on a Sunday (like most are). From Monday until Wednesday you want to be keeping things relatively similar to your normal nutrition routine. However, you will benefit from gradually beginning to consume additional carbohydrates so that when you begin carbohydrate loading, your gut won’t be working as hard to accommodate for the extra carbohydrates and calories. There is no set guideline on the amount, just consciously add carb volume throughout the day.
From Thursday onwards this is where you want to be taking your carbohydrate loading more seriously. Begin by consuming at least 5g of carbs per kilogram of bodyweight, whilst maintaining your other macronutrients (fats and protein); by increasing your carbohydrate intake and maintaining fats and protein, your body is going to function better. However, from Friday you will want to increase your carbohydrate intake to between 8-10g of carbs per kilogram of bodyweight. Whilst doing so you should reduce your fat and protein intake as these will slow down digestion, subsequently slowing down your glycogen absorption (carbohydrate). Carb loading isn’t about cramming as much food in as you can, you need to shift your daily calories around to a high carb low protein low fat diet.
The day before your race, typically Saturday, you want to keep your nutrition the same as Friday with a few nuances. You should have your heaviest meal at lunch and a lighter meal in the evening; this allows time to completely absorb the carbs and reduce the likelihood of digestive issues on race day. In addition to your high carb intake you should remain hydrated throughout the day by drinking plenty of water (as well as electrolytes). Being better hydrated will increase your blood plasma levels which helps with oxygen delivery to your muscles, increasing performance and delaying cramps and fatigue.
If you are travelling to a race and you’re staying away from home in a hotel or B&B then make sure you’re planning ahead. This could be prepping your high carb meals on the days prior to travelling so you can avoid expensive service station or big city quick food! If you’re opting for a meal out the night before the race make sure you book this ahead and ensure the menu caters to your fuelling needs. Restaurants are often fully booked with racers the night before as everyone has the same idea!
Race day is here and you’re probably wondering what to eat to avoid the ominous gastrointestinal distress. Have no fear, here’s what race day should look like, with examples of what to eat following. Breakfast is important because it replenishes your liver glycogen. Carbohydrate is stored in the liver but, during the night, the brain uses this carbohydrate. So when you wake up, there is not much left. Since this will delay the point at which you bonk, it is important to eat a carbohydrate-rich breakfast.
You can implement the 2x2 rule. 2g carbs/kg/bodyweight eaten 2-3 hours before your race. Think easy to digest carbs (bread, bagels, crumpets, liquid), with a mixture of glucose and fructose if possible (add jam, honey, syrup etc).
Remember to consider logistics for hotel/travel etc too! Upon waking up ensure you’re drinking water with electrolytes slowly across the morning, making sure you’ve finished this drink 45-60 minute before your race starts.
A small carbohydrate top-up (20-40g of an easily digestible carb source) can help maximise your body’s available energy at the start line.
This top-up helps maintain stable blood glucose and spares muscle glycogen, crucial for endurance performance.
Taking caffeine around the same time (typically 3–6 mg/kg body weight, depending on tolerance and experience) can enhance alertness, reduce perceived effort and improve endurance, helping you hit the ground running, literally!
30-60 mins before start: 100-300mg caffeine (optional) 15-30 mins before start: 20-40g carbs (gel or chew works best)
What carb sources should you consume?
The type of carbohydrates you should aim to eat are what we call simple carbohydrates (as opposed to complex carbohydrates); this basically means they are faster digesting, again causing less stomach issues. So what simple carbs should you aim to include in your carb loading:
white rice
white pasta
white bread
potato (skinless)
bagles
bananas
orange juice
carb drink mix
sports drinks like lucozade and gatorade
honey
jam
rice cakes
low fiber cereal
crumpets
Summary:
Mon-Wed begin to increase carbs slowly
Mon-Sun consume 350mg-500mg of beet shot every day
Thursday increase carb intake to 5g per kg of bodyweight, slightly reducing fiber, fat and protein intake
Friday & Saturday increase carb intake to 8-10g of carbs per kg of bodyweight
Heaviest meal the day before at lunch
Increase water and electrolyte consumption the day before
Plan meals ahead if you’re travelling the day before
2g carbs/kg/bodyweight eaten 2-3 hours before your race
30-60 mins before start: 100-300mg caffeine (optional
15-30 mins before start: 20-40g carbs (gel or chew works best)
Drinking water with electrolytes slowly across the morning, making sure you’ve finished this drink 45-60 minute before your race starts
Replenish glycogen stores post race with a high carb meal with plenty of protein to kickstart the recovery process
