Fuelling on the Run

If ya’ll remember back to the very first vlog I did on tips for long distance runners (feels like eons ago!), I had mentioned briefly about the importance of maintaining blood sugars and hydration during your event. The primary concern for marathon runners nutritionally while performing, is the intake of carbohydrates, fluids, and the electrolyte, sodium. Why is this? After about 60-90 minutes of prolonged exercise, your body starts to use up its carbohydrate/energy stores in your liver and muscles; and unless you’re super-human, you will also have some sort of sweat action happening. If you keep running, and this is left unattended, your performance will decline and your body may begin to shut down depending on the situation. In order to prevent fatigue, as well as, maintain a high level of performance, it is recommended to fuel on the go with carbohydrates, fluid, and electrolytes during your race. For most of you ultra-marathon runners, an hour is only a fraction of your race, so refuelling and rehydrating while running should be a key part of your nutrition strategy.

Here is what the research is saying and some ‘eating on the go’ strategies…

First off, let’s focus on carbohydrate (CHO) intake. It is recommended that 30-60 grams of carbohydrate (and in some instances, 90 grams of multiple transportable carbohydrates) be ingested every 60 minutes after the first hour of running. This is done to help improve performance by preventing hypoglycemia and maintaining high levels of CHO oxidation. Basically, it keeps your muscles firing on all cylinders by making sure that energy is available to use. However, eating foods while running isn’t always the easiest task. Some of the more popular products that an athlete will use during an endurance event include sports bars (ex: Powerbar, Clif Bar), sports drinks (ex: Gatorade, Powerade with 4-8% CHO), fruit juice, energy gels, jelly beans, gummy bears, fig bars, jam sandwich on white bread, bananas, and pretzels. There has also been a rise in the use of raisins, honey packets, and sugar cubes.

While there are many options, what you choose to use is dependent on what your body can handle and sometimes can boil down to convenience. It might be easier to carry a sports gel or handful of raisins in your pocket rather than a couple of bananas. Generally, most of us will have eaten raisins and bananas at some point in our life time, so they shouldn’t be too harsh on our stomach to ingest while performing. You would need about 2-3 medium bananas or 1/3 cup of raisins to put you in that 30-60 grams of CHO range. Sports gels are smaller, easy to handle, concentrated sources of glucose that can contain anywhere from 20-50 g of CHO depending on the product brand. They are super convenient and take little effort to ingest. But some runners find that they just can’t handle this sort of carbohydrate ingestion because it is more concentrated than your stomach may be used to and can lead to some intestinal discomfort. Fruit juice is also one of those food sources that could cause some stomach upset as it contains about 8-12% of varying types of carbohydrate and can be harder to absorb with the higher CHO content. Sports drinks are popular in that they are palatable, easy to ingest, and contain an adequate load of carbohydrate at 4-8%.

One of the bigger challenges a runner can face is to train your body to accept food during exercise. It is important to take the time and experiment with various foods or supplement products during exercise to determine which works best. What you should be aiming for is something that is high in carbohydrate and low in fat and protein, making sure to drink some fluids with whatever it is you choose to ingest. Fat, protein, and fiber naturally slow down the digestive process which isn’t ideal when you are trying to get energy as quickly as possible. This can also lead to some of that stomach upset that could split your focus between gastrointestinal pain and the determination to run. During exercise, the blood supply in your body is shifted toward your working muscles and away from your digestion tract making proper digestion even harder, so we want to be as nice to our body as possible by eating nutrients that it won’t have to work hard to absorb. Ever heard of the ‘runners trots’ or ‘runners gut’? These can involve more stops at the bathroom than you want to experience during a race. However, if you know that your body can handle certain nutrients and you feel you perform better with them, then do what is best for your performance! Nobody knows you like you.

Fluid intake is a bit of a different story. The single most important factor associated with sustaining a high level of athletic performance is maintenance of blood volume during exercise via proper hydration. There is no magical amount to focus on as each individual is different in their needs, as well as, their amount of sweat loss. Requirements can range from 0.5 – 2.0 L/hour and is dependent on duration of exercise, environment, temperature, and individual characteristics. A runner can estimate the amount of loss they have had during exercise by weighing their body before and after a run, taking into account any fluids put in during exercise. Weight loss equals fluid loss and this needs to be replaced to rehydrate and maintain performance. For 1 lb of weight loss, a runner should consume an extra 2-3 cups of fluid gradually over the day. Sweating is a natural phenomenon that allows your body to maintain an appropriate internal temperature. With sweat comes the constant loss of fluid and electrolytes, that if not replaced, can throw off your game by causing dizziness, fatigue, headaches, an increased heart rate, and in some cases, heat stroke. It is important to determine an appropriate fluid strategy for your race that has been practiced in training, is at a rate that is comfortable for you, and practical enough to replace those losses of fluid through sweat.

Care needs to be taken in not over-hydrating your body as this can cause hyponatremia (dilution of sodium levels) which can be serious. A rule of thumb is to not drink so much fluid that it causes you to gain weight during an event. It also is beneficial to the athlete to drink fluids that contain electrolytes, that of most importance being sodium, as this is lost through sweat. If your fluid choice doesn’t contain electrolytes, you can add your own with a shake of salt or invest in some electrolyte products that are made by sports nutrition companies. Most runners go-to choice for fluid is straight up H2O and preferably of a cooler temperature. But there are many fluid choices out there to choose from that can fit your nutrition needs and work for your body. Of note, a product such as a sports drink will contain fluid, electrolytes, and carbohydrates making it a single convenient source for all three. These tasty fluids are beneficial in that they are specially formulated to keep an athlete going. As mentioned, they provide an adequate amount of carb (4-8% carbs for volume), but are also in themselves a fluid and contain electrolytes (especially sodium and potassium) that will help with your fluid balance during your run.

Bottom line is, there is no right way to do this. It is important to get to know your gut during training runs and experiment with different fuelling options to figure out what it can handle. The quicker you know what works and what doesn’t, will allow you to create the best nutrition plan come race day. If you are looking for a more individualized plan for your fuelling on the run strategy or just have some more questions about performance and nutrition, make a quick call to your local sports dietitian or come see me at STRIDE.


– Beck, K. L., Thomson, J. S., Swift, R. J., & von Hurst, P. R. (2015). Role of nutrition in performance enhancement and postexercise recovery. Open Access Journal of Sports Medicine, 6, 259–267. http://doi.org/10.2147/OAJSM.S33605

– Burke, L., & Deakin, V. (2015). Clinical Sports Nutrition. 5th ed. McGraw-Hill Education (Australia) Pty Ltd.

– Dada, J.H. (2010). Marathon fueling – runners need proper nutrition and hydration for the 26.2 Mile Stretch. Today’s Dietitian. 12 (3): 36. http://www.todaysdietitian.com/newarchives/030810p36.shtml  

– Position of Dietitians of Cananda, the Academy of Nutrition and Dietetics and the American College of Sports Medicine. (2016). Nutrition and Athletic Performance. www.dietitians.ca/sports