Should you carbo load before a marathon?
Athletes of all levels often hear the phrase “carbo loading,” but what does it truly mean? Whether you’re a professional or recreational athlete, understanding how and when to carbo load for your marathon is important, as the strategy doesn’t suit everyone. A Baylor College of Medicine registered sports dietitian details how to properly load carbohydrates when running a marathon.
Carbo loading is about maximizing the amount of storage carbohydrates you have in your muscle and liver. It correlates with greater endurance and less fatigue, fueling the muscles to exercise at a higher intensity.
“The idea is getting as much carbohydrates into the muscle and liver so you have fuel available during your marathon,” said Roberta Anding, assistant professor of orthopedic surgery at Baylor.
How to carbo load
Anding highlights two protocols for carbo loading three days ahead of the race. The first, called low-carbohydrate availability, has the athlete restricting carbs and training hard on day one, then increasing carbs on day two to super-compensate and load the muscle. This can be difficult for some, so others might choose another practice: tapering. Three days out from the race, the athlete decreases mileage and intensity. This allows them to not train intensely to decrease their store: taper, rest, taper, rest, then add carbohydrates.
“The secret with both of these is that whether you squeeze it all out of the muscle or you taper, you have to really eat a significant amount of carbs,” Anding said. “A lot of people say they can’t do that, so you either deplete and add back carbs, or you taper and add back carbs.”
People should eat 10 to 12 grams of carbs per kilogram per day when carbo loading. An average person weighing 70 kg (~150 lbs.) would have to eat a minimum of 700 grams of carbohydrates per day. The amount of carbohydrates is key, so using either method of depleting or tapering is helpful.
Carbs to eat
The types of carbs one consumes before a marathon is crucial. This is not the time to eat high-fiber foods such as beans or high-fiber breakfast cereals, as it can exacerbate gastrointestinal distress on race day. Eat carbs such as pasta, white rice, white bread, pancakes, cereal, fruit bars, fruit leather, sports bar/gels and even hard candy when carbo loading.
“There’s a difference between what you eat on a regular basis and how you prepare for a race. You’re switching from fueling your body with optimal food versus giving your body easily digested carbohydrates so you can perform,” Anding said. “The goal on competition day is not nutrition, it’s fuel. This is why we recommend increasing carbohydrates with things like white bread, white rice and pasta.”
Athletes competing in any sport get excited and/or nervous to compete, and stress hormones don’t allow the stomach to empty well. Putting as much carbohydrates as possible in the storage tank is key instead of eating fibrous foods before a race.
“The more you add carbohydrates to the body means you can run longer and perform better without fatigue because you have these internal stores of carbohydrate – the whole goal of carbohydrate loading,” Anding said.
Who should carbo load?
Carbo loading is not for everyone. Carbohydrate needs are based on the intensity and duration of the activity and might be best for competitive runners and athletes. If you run your first marathon and you jog slowly at a 4-mph pace, you do not need to carbo load because your intensity is lower, but as you train for competition and the intensity and duration of the activity increase, carbohydrate becomes your primary fuel. This type of runner should not overdo the carbohydrates, but they might want to stop to have some carbs during the race, such as a sports drink, running gel or goo.
“Think about it like a gas tank: If you drive from Houston to Denver and you only have a quarter tank of gas, you’ll have to stop multiple times along the way, but if you fill up your tank before you leave, you’ll get further. You still have to stop and refuel, but you will get further if you start out with a maximumly full tank, and that’s how carbo loading works – maximizing that fuel tank and topping it off to go longer and further without refueling,” Anding said.
People are limited on how much carbohydrate they can store. For every one molecule of carbohydrate we store, we store three molecules of water, leading to the number on the scale to increase. This is the result of effective carbohydrate loading, which is like a sponge: when you add more carbohydrate to the liver and muscle, it pulls water along with it.
“A dry sponge is going to weigh less than a wet sponge, but the sponge itself didn’t add any mass, so the sponge didn’t have more fibers. It got swollen, but it didn’t increase its own natural dry weight,” Anding said.
Low-carb diet
Those on a low-carb or no-carb diet can train with low-carb availability, then closer to the race, they can gradually increase the amount of carbohydrates. The performance benefits are missing when running a marathon on a low carb diet, so Anding suggests increasing the carbs closer to race day.
“When you’re on a low-carb diet, you are teaching your body to burn more fat as it fuels. This is not a uniform benefit on performance,” Anding said. “Although there is data on fat adaptation – burning more fat as a fuel – there is not clear data that this has any benefit on performance.”
Regardless of the temperature on race day, hydration is crucial. Anding recommends having supplemental electrolytes during the race. If the weather is cold and you do not want water, have chicken noodle soup or broth for hydration and electrolytes.
“Hydration never takes a vacation,” Anding said. “You need hydration when it’s hot or cold.”
By Homa Warren
