Whether your goal is to finish in under 2h30, beat your personal best or simply cross the finish line, good nutrition is just as important as good physical preparation before you start your marathon.
Running a marathon places enormous demands on the human body, with high energy requirements and a significant risk of digestive and muscular disorders. A well thought-out diet in the weeks leading up to the event helps to limit these risks while optimizing physical fitness.
Preparation phase: what to eat
The aim of a good diet is to provide sufficient energy and nutrients to sustain physical effort, optimize performance and promote recovery throughout the preparation phase, right up to the big day.
A regular athlete can expend two to three times more energy than a sedentary person. To find out what daily energy intake is needed to effectively support your training load, you first need to understand the principle of the energy balance. This balance indicates the balance between calories expended, via thermogenesis, and those consumed via food.
Energy expenditure has several components.
In ascending order:
- dietary thermogenesis (8 to 15%)
- thermogenesis linked to non-sporting activities (15 to 30%)
- thermogenesis linked to physical activity (15 to 45%)
- resting metabolism (40 to 70%).1
The aim is to find the right energy balance throughout the preparation phase. A negative balance can lead to a drop in performance, persistent fatigue and an increased risk of injury.
On the other hand, a positive balance may cause the athlete to gain weight, which can have an impact on performance. Energy requirements are specific to each individual and depend on age, sex and physical activity.
It's not just a question of adding up calories: during this period of marathon preparation, your diet must be sufficiently rich and balanced to support your intensive training.
Good macronutrient management is essential for optimizing performance, recovery and body composition. Micronutrients, which are not directly involved in energy production processes, play an active role in maintaining a healthy body and are an essential part of any diet. They must be provided by a varied, balanced diet, rich in raw, unprocessed ingredients.
What macronutrient ratios
- Protein (1.6 g/kg/day): essential for muscle tissue formation, antibodies and hormones. Although debated, particularly in the field of bodybuilding, consumption during the post-workout metabolic window promotes muscle recovery and physiological adaptations. It is also advisable to spread protein intake throughout the day for more efficient assimilation2.
Vegetable proteins are not exactly equivalent to animal proteins: they are much less rich in essential amino acids, particularly BCAAs. In "classic" nutrition, a practical tip is to pair a legume with a cereal to more effectively cover all the essential amino acids needed to synthesize muscle fibers.
Nevertheless, the best natural source of essential amino acids and BCAAs is whey protein (even more so than salmon or egg, for the same grammage of pure protein). That's why it's the reference protein in sports nutrition.
- Carbohydrates (5-6 g/kg/day): the main source of cellular energy, carbohydrates are stored in the form of muscle and liver glycogen in limited quantities. Running performance depends directly on the availability of carbohydrates: before exercise, carbohydrates help to maximize glycogen reserves; during exercise, they help to preserve glycogen reserves for sufficient energy; after exercise, they help recovery and replenishment. On average, glycogen stores are depleted after 1h30 of moderate-intensity exercise. Starchy foods (pasta, rice, potatoes) often form the basis of carbohydrate intake, but it may be worthwhile to vary this with quinoa or pulses. The advantage of consuming slowly-digested complex carbohydrates is that they enable a slow release of energy for several hours after a meal.
After an endurance effort, in response to low blood sugar levels, the body may use muscle amino acids to synthesize glucose. A post-endurance carbohydrate+whey shaker helps replenish glycogen stores and preserve the athlete's muscle tissue. Proteins do not induce direct mass gain, but optimize the physiological effects of training. Their use in endurance exercise does not induce muscle gain.
Whey protein
Classic range - optimal recovery ✅
- Sugar equivalent of half an apple
- Organic, unrefined, wholegrain sugar
- Minimum carbohydrates to complement protein
Available in packs of 3 to 4.5 kg
- Fats (1-1.5 g/kg/day): provide twice as much energy as carbohydrates (9 kcal/g vs. 4 kcal/g), but are essential for maintaining a healthy body. In particular, they are the main source of energy for long-duration, moderate-intensity efforts. The distinction between different fatty acids is important from an overall health point of view. Saturated fatty acids (animal fats, butter, palm oil) should be consumed in moderate quantities, as they increase cardiovascular risk. On the other hand, unsaturated fatty acids, notably omega-3 and omega-6, are essential fats that are vital to the body's proper functioning.
For an optimal supply of omega-3, rapeseed oil represents a natural, economical and eco-responsible solution. Omega-3 food supplements are often derived from intensive krill fishing, which is disastrous for marine ecosystems. Supplementation is not always necessary.
And micronutrients?
Micronutrients (vitamins and minerals) are involved in the majority of our body's metabolic processes. They are involved in energy production, protein synthesis, immune support and protection against oxidative stress generated during exercise.
An endurance runner has high micronutrient requirements due to a more active metabolism and high losses via perspiration, particularly during intensive training sessions. Magnesium and potassium, in particular, are essential to prevent cramps and maintain optimal muscle function.
A daily diet rich and varied in fresh fruit and vegetables is the best way to ensure an adequate intake of micronutrients. Iron deficiency can lead to severe fatigue. Red meats (from time to time), lentils and spinach are ideal sources for runners.
A good practice during this phase of marathon preparation is to test your diet on a long run under the conditions of the day's effort: marathon pace, stress linked to the competition.
Whey and running?
Whey protein is often associated with muscle mass gain, but the role of whey in running will be different. Whey ensures an adequate protein intake while controlling total calorie intake, which can help marathon runners improve their fat to lean mass ratio and thus their marathon performance.
- Whey is derived from mechanically filtered milk whey, making it naturally rich in protein with high bioavailability. It is rapidly assimilated by the body, making it an interesting choice for post-workout supplementation. As an isolate, lactose is removed on the filter, making the powder easily digestible, even for the lactose-intolerant.
- During running, muscle fibers are subjected to micro-injuries. Whey provides the amino acids needed to repair these lesions, strengthening muscles and reducing the risk of post-training injuries.
Whey promotes physiological adaptation to running and reduces post-training injuries. When coupled with a carbohydrate source, it is ideal for post endurance exercise to optimize the beneficial effects of training and healthy long-term performance.
What's the right diet for a marathon?
The last few days before the competition are crucial: the aim is to saturate glycogen reserves to ensure optimum performance. Nutritional strategy during this period can vary.
In their "Préparation nutritionnelle du marathonien" (Nutritional preparation for marathon runners), the Paris Marathon recommends the Régime Dissocié Scandinave Adapté (RDSA) (Adapted Scandinavian Dissociated Diet), which consists of giving priority to fats and proteins for 3 days (D-6 to D-4), then maximizing carbohydrate intake for the 3 days prior to the race. The aim is to empty and then overload muscle and liver glycogen stocks, also known as "carb rebound".
However, this approach can cause digestive problems and muscle fatigue that are difficult to manage for some riders. We don't particularly recommend it. We prefer a simpler approach that's just as effective: without specifically reducing carbohydrate intake beforehand, it's advisable to sharply increase carbohydrate intake in the 48 hours leading up to the race: for example, to 8-9 g/kg/day in order to saturate glycogen stocks. Foods with a low glycemic index, such as oat flakes, are also to be preferred.
Organic manioc maltodextrin can supplement this carbohydrate intake, while avoiding the digestive problems often associated with too much solid food. It provides a smoother release of carbohydrates and improved digestive comfort.
During this week, avoid high-fiber foods, high-fat products and processed foods that could upset the digestive system. Choose familiar, tried-and-tested foods.
What to eat and drink on marathon day
Hydration on the big day
- 2h before: drink 250 ml of water every hour before the start. A low-carbohydrate drink can be adapted to combat stress (which consumes energy).
- Frequency and quantity: we recommend hydrating every 20 to 25 minutes. Take 3 to 4 sips of water, about 150 to 200 ml, to maintain optimal hydration levels. This is equivalent to a small cup or half a small bottle (don't wait until you're thirsty to drink!).
- Water supply: if you're aiming for more than 4 hours, it's advisable to run with a personal water supply, such as a water bottle or flask, as water refreshments on the course may be too far apart.
Food on the big day
- Frequency and type of food: consume a carbohydrate food every 40 to 50 minutes to maintain your energy reserves. In general, depending on profile and level, athletes consume between 50 and 90 g of carbohydrates / hour of effort to maintain performance. Liquid or compact foods, such as energy gels or isotonic drinks, are preferable as they are easier to digest and transport.
- Solid foods: dried fruit, gingerbread, bananas or oranges can be eaten at the feed station, but be sure to chew them well and test them before D-day to avoid digestive problems.
What to eat after a marathon
In the few hours following a marathon, the body benefits from an ideal metabolic window for recovery. After the effort, it's advisable to compensate for losses due to perspiration by hydrating regularly, and to replenish energy reserves by consuming rapidly assimilable carbohydrates and proteins to promote muscle recovery.
Nutrients consumed during this period will be more efficiently absorbed and utilized by the body. Hydrosodic losses (electrolytes + water) are naturally compensated for by a varied, balanced diet.
When it comes to post-exercise recovery techniques, the latest studies confirm that a good massage has many benefits and effectively relieves aches and pains, unlike post-exercise stretching which may even slow down the recovery process.
