Carb Loading Before a Race: Science, Strategy, and the Difference Between Men and Women

Just mention the subject of “carb loading” around an endurance athlete and prepare to hear the merits of pre-race bagels, pasta, and the like. An excuse to down bottomless bowls of pasta and scarf down an entire basket of dinner rolls all in the name of performance enhancement; where do I sign up?!

These pre-race rituals are certainly no secret as it seems almost every endurance race from marathons to triathlons now have pre-race pasta dinners (for a small fee of course). With all this hype, it is no wonder that many individuals believe that a big pasta dinner is the key to nailing a fast time the next day. Before you decide a pre-race pasta binge is the way to go, however, know that there is a science - and thus appropriate strategy - to carb loading that every endurance athlete should know.

First off, we should really break down what carb loading is and what it can do for you in terms of performance. Carb loading is a strategy to optimize the amount of glycogen stored in your muscles. This glycogen is the storage form of carbohydrates and is the primary source of fuel burned by athletes in endurance events. By upping the amount of glycogen in your muscles, you can improve endurance by 2-3%, which for some can be the differencebetween “hitting the wall” and a triumphant finish. However, carb loading isn’t always beneficial. Carb loading is ideal for endurance events lasting 90 minutes or more, which means you won’t reap any benefits from feasting on carbs the night before a 10K. In fact, for every gram of glycogen stored your body also stores about 3 grams of water. That’s all fine and well for endurance events, but that extra couple of pounds of water weight you’ll be carrying around could be problematic for activities favoring speed and agility.

If you have a race on the horizon that will last longer than the aforementioned 90 minutes, when it comes to carb loading the first thing you should be looking to switch up is your training; not your food. As an endurance athlete you should already have a very carb-heavy diet, so topping off those glycogen stores is as much about cutting back on your activity as it is amping up your carb intake. Tapering is an important part of a training plan. Tapering lets your muscles recover, but also allows your muscles to absorb as much fuel as possible. That being said, diet obviously factors in. Instead of relying on the night before the race to pack away those carbs, start loading up two or three days before your event. However, you should still be consuming about the same number of calories as you normally would, just with a higher percentage of these calories coming from carbs (about 75% depending on the sport). That in conjunction with your tapering will allow your muscles to stock away as much glycogen as possible.

Of course when it comes to carbs not all are created equal. Although normal day-to-day nutrition dictates that complex carbohydrates packed with fiber - like brown rice and whole grain bread - are the best choice, all that fiber the day before a race can be a recipe for disaster. Stick to simpler carbs like white breads and pasta to avoid spending race day running from one porta-potty to the next. Fibrous fruits and vegetables can do the same so go with tried and true foods you have trained with and know won’t cause stomach issues.

Now I’d like to apologize to all the females reading this because the sad truth is none of this really matters for you. Apparently the old adage “men are from Mars, women are from Venus,” applies to more than just issues in communication. Until recently, most studies on carb-loading in athletes were conducted on male subjects and it was simply assumed that the results applied across the board regardless of gender. Thanks to more recent research, however, we have found that this couldn’t be further from the truth. While men derive about 65% of their energy from carbohydrates during endurance activities, women only burn 56% from carbs with a whopping 41% of their energy coming from fat compared to men’s measly 29%. This difference is largely attributable to women’s higher levels of estrogen, which favors burning fat for fuel. So what does this mean for those carb-loading efforts? Men: that pasta may just give you that performance boost you’re looking for if done properly. Women: if you like carbs, go ahead and have that pasta dinner, but in the end attempting to carb-load will not make a noticeable difference in performance.

Whether you choose to take advantage of those pre-race pasta parties or not, just remember never try anything new right before a race. Bon appetite!

Interested in learning more about nutrition and running?
Come to Skirack's Wellness Series: Nutrition for Runners with Jamie Sheahan, Director of Nutritional Counseling from The Edge. Jamie will discuss food and hydration before, during, and after your race.

Date: May 10, 2018
Time: 6 - 7 PM
Locaiton: Skirack 85 Main St. Burlington, VT
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Jamie Sheahan Crosses the Finish Line at the Newport MarathonAbout Jamie Sheahan, MS, RD: 

Director of Nutritional Counseling
EDGE Personal Trainer
EDGE Group Fitness Instructor

Jamie attended Connecticut College before transferring to the University of Vermont to pursue a degree in dietetics. She graduated summa cum laude in 2011 with a Bachelor of Science degree in dietetics and then went on to complete her master’s degree in dietetics in 2013. Jamie was born and raised in South Burlington where she attended South Burlington High School. During her high school career she received 13 varsity letters in field hockey, ice hockey, tennis and golf. She also competed in field hockey and squash at the varsity level at Connecticut College. Now an avid runner, Jamie has completed 30  marathons, three ultra-marathons and dozens of half-marathons. Her lifelong passion for athletics and her experience as a Registered Dietitian provide Jamie with a unique approach to nutrition counseling and personal training and the ability to assist clients in achieving optimal heath.

Photo credit: Newport Marathon