Carb Loading for Runners: How to Prepare for Race Day

Photo: Pond5

For years, we’ve been told that carbohydrates are public enemy number one. Yes, they taste good, but they have no nutritional value and won’t keep you full for long. But you may also know that complex carbs provide energy and therefore shouldn’t be totally avoided — especially when it comes to endurance competitions. For some athletes, carb loading might even be the difference between setting a PR or getting a DNF on race day. But what’s the optimal way to make those grains and starches count? And how have the rules changed since the days of scarfing down that big bowl of spaghetti and tomato sauce? We turned to our running and nutrition experts to break down why, when and how to carbo load.

What Is Carb Loading?

Carbohydrates are a main source of energy for humans. For athletes, especially endurance athletes like marathon runners (or anyone competing for 90 minutes or more), carbs become even more essential to “supersaturate the muscles and liver glycogen stores,” says Leslie Bonci, MPH, RD, CSSD, RDN, director of sports nutrition at the UPMC Center for Sports Medicine. In order to get those energy stores to peak levels, research has shown that runners need to consume a higher amount than normal of these starchy foods in the days leading up to the big event.

Why Carb Up?

Simply put, the more energy or fuel your body has during an endurance race, the better you’ll be able to perform. More specifically, if your glycogen levels are high then you can delay fatigue longer and hopefully prevent “hitting a wall,” when your carbs stores are depleted and your body turns to muscle for energy. This process is slower, so in turn you’re forced to slow down as well.

“During marathon training we are teaching our muscles to budget their energy consumption using carbs, fat and oxygen sparingly,” says Andrew Kastor, Head Coach of the ASICS Mammoth Track Club. “Once we have depleted our carbohydrate stores during training, we need to replenish them during the taper week of the main event.”

How Do You Increase Carb Intake?

The math says that an athlete should actually gain weight the week of the marathon.”

Emphasis has generally been placed on completely depleting glycogen stores before race day, then going super carb-heavy two to three days before the race. However, Kastor and Bonci agree that in recent years, marathoners aren’t being as extreme with the process. Too many carbs can lead to sleep issues for certain individuals, plus some runners find that ingredients like the inevitable tomato sauce on top of their pasta pile can be slightly acidic in their stomach, Bonci points out.

So what carbs should you be eating? Bonci suggests one or two additional servings of the starchy stuff per meal. That can mean a half-cup of cereal, plain pasta or rice, a serving of crackers, a piece of fruit, a small glass of juice or an extra slice of bread. If you start to experience sleepless nights, bloating, and possibly even GI issues like nausea and gas, try cutting back.

But don’t be surprised if you put on a few pounds. While society may lead you to believe this isn’t a good thing, it could be an advantage come race day. “The math says that an athlete should actually gain weight the week of the marathon,” says Kastor. “The weight will come from storing water, glycogen, minerals and tiny bit of fat — all needed to fuel the runner to the finish line!”

When Does Carbo Loading Begin?

Sweet and Savory Quinoa Oatmeal
Photo by Perry Santanachote

Use your taper week — the week before your race when you’re allowing your body to recover from training — to get your glycogen levels up to capacity. Kastor recommends that mileage this week should be about 50 to 60 percent of what you ran during the heaviest training week, and you should be eating roughly the same amount of calories. So how does that work if you’re consuming more carbs? Reducing your fat and protein intake, Kastor says. “At this point protein is pretty much obsolete as we are focusing on ‘fueling’ rather than ‘repairing’ muscle,” he says. “A little bit of lean protein mixed in with complex carbs, is absolutely fine as well.”

The Last (Carb) Supper

While it isn’t your final meal ever, what you eat the night before your race does matter. This dish should be easily digestible in order to top off your glycogen levels and help your body retain fluids. “Usually a large carb-heavy meal will deliver all the needed carbohydrates to replenish any holes in the glycogen stores and will ‘empty’ from the body efficiently,” says Kastor. Just remember to avoid heavy or rich condiments and sauces — the high fat levels are hard for the body to break down.

Race Day

When the big day arrives, this is your last chance to carb up. Kastor recommends a bowl of oatmeal with brown sugar, salt and sliced bananas one and a half to two hours before start time. Prefer whole grain toast over oats? Go with whatever carbs you have the best track record with and that won’t upset your stomach.

At the end of the day, how you set yourself up for success is up to you. “Athletes need to fine-tune to find the form, amount and timing that works for them prior to a race,” says Bonci. “It requires practice — ideally over months of training — so that the hand-to-mouth exercise is as much of a priority as the training itself.”

Related Posts

Scroll to Top