Nutrition before a Marathon or Trail race

Nutrition before a marathon or a trail race

During a long-distance run, your body relies on carbohydrates and fat as fuel sources. While fat reserves are nearly inexhaustible, carbohydrate stores deplete more quickly. Therefore, beginning a race with fully stocked carbohydrate reserves is crucial. Here are some tips for optimal nutrition before a marathon or race.

Digestive issues are a common challenge in long-distance events like marathons or trail races. These races place significant demands on your body, increasing both energy needs and stress levels as the big day approaches. This stress is often amplified by the daunting distance or the pressure of achieving the goals you’ve trained weeks for. So, how can you turn pre-race nutrition into an ally for these challenges?

Running and its impact on the intestinal wall

In long-distance running, the heart directs blood primarily to major organs like the brain and muscles, especially during intense exertion. This redirection can sometimes lead to reduced blood flow to the intestines. Additionally, the repetitive jolting in running can potentially cause lesions in the intestinal wall. Consequently, it’s vital to adopt strategies that facilitate easier digestion.

Nutrition principles from 10 Days to 3 Days before the race

As race day approaches, your training should adjust to ensure peak performance. Alongside this, a good lifestyle and a balanced diet are key to integrating your weeks of training. Don’t underestimate the power of a good night’s sleep.

A balanced diet encompasses a variety of foods: starchy foods, proteins (like white meat, fish, and eggs), vegetables, fruits, and foods rich in healthy fats, including omega-3-rich oils such as flaxseed and canola. Hydration is crucial, so vary your sources: still and sparkling water, tea, and herbal tea. Moderation is key, so an occasional beer or glass of wine is fine.

To prevent digestive issues during the race, consider reducing your intake of dietary fiber. Go for easily digestible foods like white meat, eggs, zucchini, and soups. Some may opt for gluten-free choices.

For optimal carbohydrate intake, we recommend decreasing the ratio of carbohydrates and starchy foods from Day -6 to Day -4, but don’t eliminate them completely to avoid shocking your system. This reduction helps your body adapt before increasing high-quality carbohydrate consumption in the final days.

Final preparation from 3 Days to 1 Day before the race

In the final days leading up to the race, from Day -3 to Day -2, it’s essential to focus on stocking up on high-quality carbohydrates with a low glycemic index. Utilize the 4 to 6-hour metabolic window post-light training or exercise session to replenish carbohydrate stores effectively.

Favor nutrient-rich foods like steamed potatoes with their skins, sweet potatoes, semi-whole grain rice, buckwheat, quinoa, honey, and maple syrup. For a healthy dose of fructose, opt for fruits with lower fiber content, such as ripe bananas or stewed fruits like apples, pears, and peaches.

Avoid foods with a high glycemic index, including overcooked pasta, white bread, sugar, French fries, and rice cakes or cornflakes.

It’s advisable to limit your intake of vegetables, particularly raw ones and dried legumes like lentils, as they can be hard to digest. Instead, opt for gentler options like soups, carrots, zucchini, or even vegetable juices made with a juicer, which can help lower body acidity.

The key takeaway for these final days: Minimize fiber intake and focus on carbohydrates, but be mindful not to overindulge.

Optimal fluid intake strategy

Regularly hydrate with still or sparkling water, or enjoy hot beverages throughout the day. Even isotonic drinks can be beneficial.

It’s advisable to avoid sodas due to their high sugar content, which can hinder nutrient absorption. Also, steer clear of fruit juices (which are both sugary and acidic) and milk-based drinks, as lactose digestion can be energy-intensive

Nutrition on the day before a marathon or Ultra run

Continue following the dietary routine established in the previous three days. Ideally, limit your intake of fiber, spices, unsaturated fats (such as fried and prepared foods), and oily foods. Be cautious not to overeat, as this can overly tax your digestive system. Also, avoid introducing new foods that you’re not accustomed to, as this could lead to digestive discomfort.

Race day morning nutrition

It’s essential to eat about 3 hours before the race start, sometimes even earlier. While it may require waking up at an unusually early hour, it’s a step you won’t regret. Start by drinking water or herbal tea, and avoid going back to bed after eating.

Stick to foods you’ve previously tested before races or training sessions. This is not the time to experiment, as you don’t want to risk the efforts of weeks or months of preparation.

Since you’ve already loaded up on carbohydrates in the days leading up to the race, there’s no need for a heavy meal. In fact, a lighter meal is preferable to avoid digestive issues.”

Breakfast ideas before exertion:

  • Beverages: Tea, herbal tea, coffee, water.
  • Carbohydrates: Bread, pancakes.
  • Energy boosters: Sports cake, energy cake.
  • Sweeteners: Honey, maple syrup, jam.
  • Proteins: Ham, tuna fish.
  • Fruits: Stewed fruit, sliced banana.


  • Fruit juice (acidic, quickly absorbed sugars).
  • Soda pop.
  • Raw fruits.
  • Oily foods.
  • Whole grain bread (high in fiber).
  • Dairy products.

Hydration Tips:

  • Drink a moderate amount of water every 30 minutes, aiming for a maximum of 0.5L/hour, or up to 0.7L/hour in extreme heat. Over-drinking can lead to hyponatremia.

And that’s it!

There will still be opportunities to fuel up during the race.

You’re now fully prepared for the start, whether it’s a marathon, trail race, ultra, or triathlon. For personalized training and nutrition advice, download the RunMotion Coach app. It includes all pre-race nutrition recommendations. On your marks, get set… go!

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Mailis Durif-VarambonMailis grew up in the mountains, where she went hiking and biking every weekend. She loves outdoor activities where she can relax at the end of the day. At RunMotion Coach, she is responsible for communication management.