The Big Three in Fueling Endurance Events

By Kellsey O’Donnell, MS, RD, LDN

Whether on two feet or two wheels, it seems like some sort of endurance event is taking place almost every weekend recently!  As we know, this welcoming community is extremely encouraging and motivating, however the desire to commit to a lifestyle of endurance training requires comfort and enjoyment of the sport itself.  Of course, proper physical training to reach your goals is necessary, yet many people accidentally bypass the importance of nutrition on their path to hopeful success.

Some important factors to consider when talking nutrition for these events are carbohydrates, water, and electrolytes.  Carbohydrates play an important role in building up our energy stores in our muscles and liver.  Our bodies pull from these storage units throughout the entirety of the exercise bout.  It may seem obvious to stay hydrated before and during training and the event itself, however it is equally as important to take in electrolytes to stay balanced.

You may have heard of the concept “carb loading”.  This practice in the days leading up to an endurance event has seen to improve performance by 2-3% in events lasting more than 90 minutes.1   However, carbohydrate consumption during exercise itself may also improve performance over time.  One study showed that ingestion of 0.2 g of carbohydrates per kilogram body weight every 20 minutes during an 80 minute treadmill run improved running time trial performance when compared to ingestion of water only.2   This can be done by testing out GU, Clif Bloks, Sport Beans, or even something as simple as raisins, whatever it may be that works for you!  Between brands, they all serve the same purpose.  Some people like having something to chew on, while others prefer a gel for easier consumption.  Use your training to test a few brands and see what works best, so that by the day of your event you’ve got your routine down pat.


During events in which the body is taxed over a long period of time, athletes can run the risk of dehydration if not properly hydrated.  However, the opposite problem, known as hyponatremia, displays similar symptoms!  Hyponatremia is the when you are essentially overhydrated, enough to dilute the sodium in your blood, which is responsible for proper muscle contraction, among other things.  Hydration is important to replace the sweat losses, but with sweat loss also brings sodium loss.  So, it is very important to be aware of the types of fluids you are consuming, whether it be just water or a sports drink containing electrolytes.  A great trick to test your dehydration is to simply weigh yourself before and after exercise.  Any loss of body weight greater than or equal to 2% is considered dehydration that could affect performance, and ultimately health.  During events lasting longer than 60 minutes, consider alternating between water and sports drinks, in an effort to maintain hydration and electrolyte levels in your body.

This healthy combination of carbohydrates, water, and electrolytes may just be the extra push that you need to hit the ground running!  Remember, everyone’s body is different, so testing various methods before committing to one is vital to optimal performance.

For more information on nutrition tips and tricks, or to create an individualized nutrition program, schedule an appointment with our Registered Dietitian, Kellsey O’Donnell, MS, RD, LDN, at


  1. Jeukendrup, A. E. Nutrition for endurance sports: Marathon, triathlon, and road cycling. Journal of Sport Sciences. 2011;29(S1): S91-S99.

Too, BW, Cicai, S, Hockett, KR, Applegate, E, Davis, BA, Casazze, GA.  Natural versus commercial carbohydrate supplementation and endurance running performance.  Journal of the International Society of Sports Nutrition, 2012;9(27):1-9.