All too often, runners think that fatigue is due to a lack of fitness, which urges them to double down and train more. The catch? The more you train, the more you develop acute fatigue, making recovery even more paramount. And the reality? Fatigue, especially the type that comes on at mile 20 of a marathon, is not always due to a lack of fitness.
So it’s time to dial in on your fuelling. Alongside sufficient rest, your energy intake plays a key role in supporting your training and overall health and provides the foundation for better recovery. That energy intake should include carbohydrates, proteins and fats, as well as hydration and micronutrient support. Most runners are not under or overtraining for a marathon, but rather underfuelling – and because of that, they’re not recovering.
If you want to improve fatigue resistance in the marathon, you need to think beyond mid-race gels and focus on consuming nutrient-rich foods that provide a consistent stream of energy throughout your day and training cycle. Here’s how.
Energy availability – the foundation for fighting fatigue
To understand the relationship between fuelling and fatigue, you first need to understand energy availability. In short, energy availability is the amount of dietary energy – in the form of calories – that your body has to have to maintain its physiological functions, after accounting for exercise. You need sufficient energy to support recovery, adaptation, hormone function, immune health, bone integrity and overall durability and resilience.
If your daily energy intake does not support your training load, your body compensates by slowing recovery, down-regulating hormonal systems and experiencing more ‘high stress” responses. Regularly underfuelling could also disrupt your sleep, as well as your pace when you try to run faster or farther.
Prolonged low energy availability often leads to missing more days of training due to excessive fatigue and can even increase the likelihood of illness or injury. If you get sick, injured or simply carry excess cumulative fatigue because you’re underfuelling, your chances of toeing the start line healthy decrease.
You build your marathon performance on consistent training – and you also build consistent training on adequate daily energy intake.
Why you need carbohydrates around your runs
Before long runs and key interval sessions, you need to eat carbohydrates. Doing so boosts blood glucose and liver glycogen, which are important for maintaining energy for your entire body, including your brain and nervous system.
After runs, carbohydrate intake also helps to restock muscle glycogen stores. The immediate post-run window matters because glycogen resynthesis rates are elevated in the first 30 to 60 minutes. A practical target for your post-run meal or snack is between 1g and 1.2g of carbohydrate per kilogram of bodyweight, combined with approximately 0.5g per kilogram of protein.
Post-run protein is just as important as post-run carbohydrates because it helps to reduce fatigue by supplying the amino acids needed to repair muscle and rebuild mitochondrial proteins that power energy production. Additionally, it helps to shift the body out of a breakdown state and supports glycogen resynthesis and recovery for your next session.
However, recovery doesn’t end with one initial post-run or post-race meal. Steady carbohydrate intake for the next 24 to 48 hours helps to restore and maintain muscle glycogen for upcoming workouts and races. If you underfuel after a long run, fatigue compounds throughout the week.
A daily approach to extended recovery includes:
High-fibre complex carbohydrates to replenish glycogen after workouts and throughout the week – think whole grains, vegetables, fruits, beans and lentils.Protein to repair muscle tissue and produce energy (aim to hit between 1.8g and 2g per kilogram of bodyweight per day), spread evenly throughout meals – this may look like 20g to 30g per meal.Fluids and high-fluid foods to maintain hydration – specifically, between 3l and 4l per day.Antioxidant and anti-inflammatory foods incorporated into meals throughout the training week. For example, tart cherry juice and blueberries provide polyphenols that may help to lower exercise-induced inflammation and muscle soreness, while broccoli sprouts are rich in sulforaphane, which is a compound linked to cellular antioxidant pathways. Dietary nitrates, found in beetroot, spinach and arugula, can also enhance nitric oxide production, which improves blood flow efficiency.Because iron deficiency can be prevalent in endurance running, it’s also smart to include iron-containing foods in your diet, including meat, poultry, beans, beets and leafy greens.Why you should go beyond pasta in your pre-race carb load
Glycogen is the primary fuel source at marathon pace. If your glycogen stores drop too low, your pace slows and perceived effort increases. Carb loading can increase muscle glycogen stores, providing an easily accessible energy source for your race.
Aiming to consume between 8g and 10g of carbohydrate per kilogram of bodyweight in the 24 to 36 hours before a marathon is a good starting point for many runners. To do this, simply increase the relative portion of carbohydrates during meals and snacks throughout the days leading up to the event, rather than only loading up on pasta the night before the race.
In the final 24 hours before your race, be mindful of excess fibre intake. Dramatically increasing foods such as vegetables and beans right before the marathon can increase your risk of GI distress on race day. Focus on familiar foods, moderate portions and lower-fibre carbohydrate sources – like waffles, bagels or toast – as you get closer to race day.
On race morning, many runners struggle not with what to eat, but when to eat. A practical target is between 2g and 4g of carbohydrate per kilogram of bodyweight two to four hours before the start. The closer you are to the start, the smaller and more easily digestible the meal should be. For example, four hours before, you might have porridge with maple syrup and fruit, but two hours before you might opt for toast with jam.
Consistently supporting daily energy intake, carbohydrate availability and recovery through nutrient-dense foods across your race build-up has more influence on how you’ll feel at mile 20 of the marathon than you might think. It could be the missing factor that will help you to avoid hitting the wall and instead run your best race yet.
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