A Sports Nutritionist on Fueling for Half- and Full-Marathon Races

Lori Nedescu, MS RD CSSD
by Lori Nedescu, MS RD CSSD
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A Sports Nutritionist on Fueling for Half- and Full-Marathon Races

Consuming enough calories and maintaining hydration to meet energy needs is key to making your race day a success. This means fine tuning the method and amount you consume to be energetic while avoiding hitting the wall, being sloshy or running to the portaloo.


Energy gels are the preferred fuel for most runners due to the ease of carrying and consuming them. They are also fast acting, allowing you to feel the energy burst quickly. Most gels contain ~24 grams carbohydrate each. To get the suggested 45–60 grams of carbs/hour, you’d need to consume about one every 25 minutes of your race.

If gels have been tolerated poorly in the past, try a different brand as different brands use different sources of sugar (honey, maple, maltodextrin …) in the ingredients. Your body might tolerate one type of sugar better than another. Because gels are concentrated sources of sugar, make sure to consume with water to facilitate digestion.

If, however, you plan on being out for six hours, that goes beyond how long the body should work on sugar alone, adding protein and sustenance like a bar will control hunger and limit tissue breakdown during the endurance event.


Sport drinks are another good choice, however; most sport drinks are less concentrated meaning you’d have to drink ~33 ounces/hour to meet your energy needs. While this is in line with the suggested amount of water one should drink per hour of exercise, most runners would encounter GI problems by consuming that much liquid during a race. Be aware of how many fluids your body can tolerate at race pace. Consuming gels while taking frequent sips of a diluted sport drink is a great way to get a mix of sugar, electrolytes and hydration to support your race.

Other sources of race fuel can be whole foods like bananas and dates. While these options are great sources of quick carbohydrates, they may not be ideal for a runner who struggles to chew at race pace or doesn’t want to carry a pack of snacks for the race. Think about what you can realistically carry during the race and research what will be offered at aid stations along the route.

Remember that what and how much you consume during the race depends on many factors including weather, training status, electrolyte needs, experience, weight, goal time and personal tolerance to fuel. What you eat leading up to the race plays a role as well. Make sure you go into your race well hydrated and fueled, with carbohydrate stores topped off. Just as you log miles, track repeats, take rest days and calculate paces, you must also train your nutrition habits. Proper race-day fueling should be practiced throughout your training program to be effective for your individual needs, tolerances and preferences when race day comes.

If you’ve been struggling to meet your half- or full-marathon race goals, it may be as simple as changing the way you’re fueling the effort. Enlisting the assistance of a professional is always your best bet. A sports dietitian/nutritionist can help you fine tune fueling habits, increase energy, improve body composition and increase your chances of performing at your full potential.

Reference this guide to see if you consume enough carbohydrates during your race.

About the Author

Lori Nedescu, MS RD CSSD
Lori Nedescu, MS RD CSSD

Lori, MS RD CSSD is an accomplished sports dietitian; she holds a Master’s Degree in Human Nutrition and Certification as a Specialist in Sports Nutrition. As a current professional road cyclist and previous elite marathoner and ultra-runner, Lori knows firsthand that food can enhance or diminish performance gains. She understands the importance of balancing a quality whole food based diet with science-backed performance nutrition and strives to share this message with others. Learn more about her @HungryForResults.


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