What should you eat before a marathon?
© ASOIn a few weeks, you’ll line up for the race you’ve been preparing for over many months. Whether it’s a marathon, half marathon, 10K or trail race, running is the ultimate endurance sport and demands a considered approach to what goes on your plate. And that means more than just the day before. Pre-race nutrition is one of the factors that can make a difference to performance.
Why adjust your diet before a race?
The muscles’ main fuel is glycogen, which the body produces from the carbohydrates in food. In the days before a long, intense effort, the aim is therefore to optimise glycogen stores and build up a reserve that can be drawn on during the race.
Gastrointestinal problems are also extremely common during endurance events, for a variety of reasons, and are often enough to force a DNF. To reduce the risk, your pre-race diet should limit fibre and anything that may irritate the gut.
The key principles of pre-race nutrition
Starchy carbohydrates should take centre stage in the meals leading up to race day, such as rice, sweet potato and quinoa, while fibre intake should be reduced by limiting raw fruit and vegetables. Runners with sensitive guts may also want to avoid gluten and dairy products.
Some athletes advocate the Scandinavian dissociated diet, starting six days before competition. It is split into several phases:
➜ The first phase, low in carbohydrates, lasts three days and involves increasing protein and fat intake.
➜ The following three days focus on eating carbohydrate-rich foods.
This approach is supposed to maximise muscle glycogen stores and help athletes cope with intense physical effort. It is not universally accepted, but it may be worth trying, as some athletes find it works very well for them. You’ll have to test it for yourself.
You do not have to follow such a demanding protocol to make sensible adjustments to your diet. The foods to avoid will vary from person to person: some runners have an iron stomach and can eat anything right up to race day, while others are more sensitive and need to take care in the days before a race. Knowing your own body is essential if you want to understand what you can and cannot eat.
© ASOA suggested plan from four days out to race day
This plan outlines broad nutritional principles rather than prescribing exactly what should be on your plate. As noted above, you need to identify the foods that suit you best while taking into account the advice below, which is based on reliable sources such as sports dietitians and nutritionists.
Four to two days before / OBJECTIVE
Increase carbohydrate intake to fully replenish glycogen stores within 48 hours.
Maintain acid-base balance and digestive comfort.
Four to two days before / GENERAL PRINCIPLES
Eat starchy carbohydrates at breakfast, lunch and dinner.
Add a mid-morning or afternoon snack to help fully replenish glycogen stores: fresh or dried fruit, yoghurt or plant-based milk, bread or cereal, jam or honey.
In general, choose cooked fruit and vegetables, which are easier to digest, and limit gluten intake.
Drink sparkling water, such as Quézac, Rozana or St Yorre, or still water rich in minerals, aiming for 1 to 1.5 litres a day.
The pasta myth
Pasta is a major source of slow-release carbohydrates and a staple for many athletes convinced of its benefits. And yet, its virtues are widely overestimated. While pasta does provide slow-release carbohydrates, its high gluten content can also irritate the gut.
To make pasta a worthwhile source of carbohydrates:
➜ Choose semi-wholewheat or wholewheat pasta, which is more nutrient-dense. Take care, though, if you have a sensitive gut: wholegrain cereals can be irritating.
➜ Don’t overcook it, otherwise the slow-release carbohydrates become fast-acting: al dente is ideal.
➜ Be careful with what you add: rich sauces and excessive amounts of cheese are hardly an athlete’s best allies.
➜ There’s more to life than pasta: also consider pulses such as lentils, chickpeas and cannellini beans, as well as other sources of carbohydrates including sweet potato, potato, rice and quinoa.
© ASOCarbohydrates and glycogen
Carbohydrates are often considered the cornerstone of an athlete’s diet. They can be divided into two categories according to how quickly they are absorbed in the gut:
➜ Slow-release carbohydrates, found in pasta, rice, bread and cereals.
➜ Fast-acting carbohydrates, found in soft drinks, sweets and honey.
Athletes should prioritise the first category and be wary of the second, which can cause reactive hyperglycaemia, with a sharp rise in insulin leading to symptoms such as heavy legs and reduced alertness.
Carbohydrates are converted into both glucose and glycogen.
➜ Glucose circulates in the bloodstream and plays a vital role in brain function.
➜ Glycogen is stored in the muscles and liver and provides the main fuel source for high-intensity efforts.
The more carbohydrate-rich your diet is, the higher your glycogen stores will be and the more fuel your muscles will have available. That is why it is important to eat a substantial amount of slow-release carbohydrates when you train and, a fortiori, when a race is approaching. That said, you do not need to eat starchy carbohydrates at every meal.
To maximise glycogen stores for race day, it is recommended that you significantly increase the proportion of slow-release carbohydrates in your daily intake several days beforehand, rather than waiting until the day before.
Ultimately, what you eat before a running or trail race is one of the factors that can influence performance. Your approach should be tailored to your own needs and sensitivities, while still following broad nutritional principles. To keep it simple, focus on two priorities: increase carbohydrate intake and reduce fibre intake.