How To Fuel Your Marathon

Our helpful nutritional guide to help you prepare, perform & recover from your marathon


Your nutrition will be the make or break when it comes to not just surviving the miles but actually enjoying the event when race day comes and being able to train without fatigue. We’ve put together the key nutritional considerations to help you fuel your training days and the marathon itself.


Testing nutrition strategies before race day is essential for the following reasons:

Morning fuel: Your breakfast will be one of the most important meals you consume and will ensure you are fully fuelled when you cross the start line, so make sure you are comfortable with it and it works for you.

On the go feeding: Fueling while running a marathon is key, so get confident at consuming food, gels and fluid whilst at your chosen pace.

Carbohydrate intake: Since your body can only store enough carbohydrate for up to 90-120 minutes of exercise you will need to take on 60-90g of carbohydrate per hour during the marathon to maintain carbohydrate supply to your muscles (1). If you’re not used to consuming this much carbohydrate during exercise it is a good idea to test it out to ensure the body is capable. The Science in Sport Isotonic Energy Gel provides 22g of carbohydrates without the need to wash it down with water.

Sweat rate: How much you sweat will dictate how much fluid you need to take-in. Aim to not lose any more than 2-3 % of your body mass during runs to maintain hydration and be ready to train the next day (2).



KEY CONSIDERATION  1: Why the science in sport isotonic energy gel?

Isotonic: To be isotonic a solution must have the same concentration of dissolved particles as the fluid in the cells within the body, typically this means having a tonicity between 290-310 mmol/kg.

The tonicity of a solution refers to the concentration that affects water and carbohydrate transportation across cell membranes, most importantly the movement from the gut into the bloodstream. Ultimately this will affect how quickly the gel can be used as an energy source.

The carbohydrate source in GO Isotonic Energy gels is maltodextrin which we specially select. We use one with a particular size of molecule, known as its’ molecular weight. This allows us to balance the amount of energy delivered versus how quickly it empties from the stomach. This means that you will feel the performance benefits of taking on a GO Isotonic Energy gel far more quickly than when a non-isotonic gel is consumed. The risk of upsetting your stomach is also much less (3) and best of all, you don’t need to wash it down with up to 7 oz of water!


Breakfast: Have breakfast 2-3 hours before the race. This should be mainly carbohydrate based as our liver glycogen stores decrease over night. Don’t leave breakfast too late as this could cause stomach cramps early on in the race. This should involve normal breakfast foods that you’re accustomed to such as toast, cereals and juices.

Hydration: Pre race hydration is key. Aim to drink 17 oz -34 oz of fluid in the build up to the race, ideally 500ml 2-3 hours at breakfast and 500ml in the build up to the event. Don’t drink just water, include juices and electrolytes (4) to promote energy and hydration.


When running a marathon, focus on both hydration and carbohydrate intake. Our bodies can absorb around 60-90g of carbohydrate per hour, so know how long you’ll be running and pack enough nutrition to see you through to the end (5). Here, caffeine should be taken in the last hour of the race to push you through to the end.


After training or racing over long or short distance the body will be in a state of depletion; to reduce fatigue, the risk of injury and promote physiological adaptations it is important to recover well by refuelling and getting enough rest. Consider these three key points for the ultimate post-run recovery:

Refuel: The capacity of your muscles to absorb and store nutrients is increased 30-60 minutes post-exercise, so it is important to replace carbohydrates and provide protein and electrolytes within this time. This can be done with “real food” such as carbohydrate (e.g. rice, pasta, breads etc) and protein options (e.g. greek yoghurt, chicken, fish etc) or a carbohydrate-protein shake.

Food: Take on a full carbohydrate based meal within 1 hour of finishing a tough training run or race. This should also include a source of protein and plenty of vegetables.

Always plan ahead: Pre-planning your meals or snacks after training ensures that you can take advantage of the 30 – 60 minute recovery window. If you have to drive back from the race or are heading out to training straight after work, ensure you have the appropriate meals with you.


  1. Jeukendrup, A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine44(1), 25-33.
  2. Casa, D. J., DeMartini, J. K., Bergeron, M. F., Csillan, D., Eichner, E. R., Lopez, R. M. & Yeargin, S. W. (2015). National Athletic Trainers’ Association position statement: exertional heat illnesses. Journal of Athletic Training50(9), 986-1000.
  3. Zhang, X., O’Kennedy, N., & Morton, J. P. (2015). Extreme variation of nutritional composition and osmolality of commercially available carbohydrate energy gels. International Journal of Sport Nutrition and Exercise Metabolism25(5), 504-509.
  4. Baker, L. B., & Jeukendrup, A. E. (2014). Optimal composition of fluid‐replacement beverages. Comprehensive Physiology, 4, 575-630
  5. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the academy of nutrition and dietetics, dietitians of canada, and the american college of sports medicine: Nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics116(3), 501-528.