How should I eat when preparing for a marathon?

Joëlle Flück 6. March 2019

Unlike a 10-km run or half marathon, the importance of nutrition increases with longer distances. Your diet can and should be tailored to factors such as the scope of training, individual training objectives or stimuli, as well as your recovery. 

Presented by Swiss Sports Nutrition Society

Adjustments to your everyday diet

When you are faced with the challenge of a marathon, you should not only take your training into consideration, but also your nutrition and recovery. The scope of training usually increases, which means you will be running more kilometres each week than when preparing for a 10-km race. These additional kilometres place a greater burden on your muscles and your body will require more calories due to the increase in scope. It is therefore worthwhile taking specific regenerative measures when it comes to your diet, such as replenishing your carbohydrate reserves, compensating for any fluid deficits, and making sure you eat enough protein. These three factors will help you to recover better from the training unit. To reduce the risk of overload symptoms, it is important that the extra calories you consume for the increased scope of training are in the form of nutrients. 

Nutrition during long units

The first thing you need to consider is the actual objective of the respective unit. Do I want to do fat burning training? Should I introduce muscular stimuli to simulate the last kilometres of a marathon? Do I want to test my competition nutrition, or do I actually want to run close to my marathon pace now and then? Each question gives rise to a different nutrition strategy. 

If burning fat is your priority, then completing a «long run» before breakfast is common. You will need to drink water to correct the fluid deficit that develops during the run. Quality or speed here is of secondary importance. The primary goal is to run for as long as possible in this fat burning zone and get the body used to it. 

If, on the other hand, speed is of greater importance, then you won’t normally complete a «long run» on an «empty stomach». This means eating a small or normal breakfast containing carbohydrates before the run. During the run, you also need to ensure that you consume enough carbohydrates with the aid of gels or sports drinks, as well as enough fluids. These measures will help you to maintain your speed and ensure good quality training. 

Test your competition nutrition

To be successful on the day of the competition, you need to prepare and practice your competition nutrition. And this is completely irrespective of the goal you are pursuing. To start with, you need to decide whether you want to fuel yourself with the organiser’s official products, or whether you want to rely on your own mentor or products during the race. If you choose the first option, you need to find out what products are being offered and at what intervals. Secondly, it is worth checking whether bottles or beakers are on offer. Drinking from a plastic beaker during a competition can be a real challenge. Thirdly, you need to test and practice your competition nutrition (your own or that from the organiser) during training. This can be well combined in a faster, longer training unit in which your speed is more like that of a marathon pace than a relaxed continuous run. The faster you run, the greater the impact on your gastrointestinal tract, which in turn further complicates the absorption of fluids and carbohydrates. Not only drinking properly but handing over a drink bottle or opening a gel can be practised at high speed, and the absorption of fluids and carbohydrates in your gastrointestinal tract will improve the more often this is simulated. 


How much do you need?

During a marathon, you will normally need to consume 30 to 60 g of carbohydrates per hour in the form of a gel or sports drinks. These are spread out to ensure you don’t have too many carbohydrates in your gastrointestinal tract at once (e.g. 20 g of carbohydrates every 20 min). The amount of fluids you lose depends on your sweat rate and the outdoor conditions on the day of the competition (e.g. temperature, humidity, wind). As a rule of thumb, you will normally need 4 to 8 dl of fluids per hour. You can calculate your own personal fluid intake with the help of the hydration calculator


Optimal nutrition is a crucial piece of the mosaic when it comes to successful marathon preparation. It supports your performance and recovery and depends, among other things, on the scope of training and respective training goal. General recommendations are therefore not possible. It is far more a question of tailoring the specific nutritional recommendations to your own needs and circumstances. 

You can find more on sports nutrition under: 
By the way: on 6 June 2019, the 4th annual meeting of the SSNS will take place with interesting presentations.