Successful Carb Loading for a Successful Marathon!

We are a mere 2 days away from the Chicago Marathon! Many of you know I have been training since June in preparation for this race.  Posts about tapering, training and all things marathons have been taking over my blog. I promise, I’ll talk about yoga after this marathon.  The finals days before the marathon don’t include much running.  Runs are less than 3 or 4 miles and they are easy.  The focus of preparation now is rest and eating well.  And by eating well I mean, carbohydrate loading.  This doesn’t mean eat copious amounts of carbohydrates on end the days before your marathon.  Ok, ok it kind of does.  You need to be SMART about this, and what you eat and why.  So let’s discuss some basics.

Glycogen. This is what your muscles store and burn while you run. Glycogen is the most accessible form of energy in our bodies. This means our bodies can easily convert glycogen to fuel.

The Wall.  This is what happens when your body runs out of glycogen. Your body slows down because it has no more glycogen to convert to fuel.  Now your body must convert fat to fuel.  This is hard for the body to do so it slows down as a result of this process and you see your pace slow.

Foods.  Typical foods you want to eat include pasta, rice, potatoes, bagels, bread, tortillas, oatmeal, yogurt, juice, pancakes and waffles, and rice noodles.  Bananas and fruits like apples, peaches and pears with skins peeled are good options.  Peeling the skin eliminates some of the fiber on the fruits so you get mostly carbohydrates.  Avoid fats and protein like oils, cheese, and cream sauces because they take longer to digest and fill you up quicker than carbohydrates.

Ok. So how much should you eat?

You need to carbohydrate over the course of days since you won’t get enough carbohydrates from one meal.  Ideally you should start this process two to three days before your marathon or race.  At this point 85 to 95% of your calories should come from carbohydrates. Runner’s World’s Monique Ryan, R.D., author of Sports Nutrition for Endurance Athletes runners sums it up in the following:

Ryan recommends eating about four grams of carbs for every pound of body weight (for a 150 pound runner that’s 600 grams—or 2,400 calories—of carbs per day).

There are plenty of websites out there that help you calculate how many calories you should consume during a carb load.  A simple Google search will give you quite a long list.  I used the endurance calculator to determine how much I should consume. This site was recommended in a Runner’s World article, Fill ‘Er Up.

The Endurance Calculator website is simple, it asks for some basic information including your age, your weight, your gender, your resting heart rate and your marathon goal pace.  The result is the following:

Endurance Calculator

Here is the break down.  It determines a conservative goal time for me based on the information I put in.  The conservative pace is what I may achieve if I had done no carbohydrate loading and no fueling during the race.  The aggressive pace is the fastest theoretical pace I could achieve with maximum carb-loading.  Both of these assume you are not hitting the wall. The calories reflected are how many calories from carbohydrates I would need to achieve those goals.  However the site does say the following:

 The number of calories of carbohydrate indicated by the calculator for a particular target pace represents the total minimum excess, over and above normal caloric requirements, that should be consumed as carbohydrate (neither fat nor protein can be substituted for carbohydrate in carbohydrate loading) during the loading period.

Now don’t be surprised if you gain weight during this process.  You may gain at least 4 pounds. This is your body demonstrating that you have carb loaded and hydrated properly as you have both water and carbohydrates stored.

I personally like to see examples of what a typical day of carbohydrate loading should look like for a runner.  It helps me to visualize what is appropriate and what my body needs.  I can then easily adjust it for my schedule and routine.  Additionally it makes it easy for me to add foods or replace foods during the meals I already eat.

The article “Fill ‘Er Up” by Dimity McDowell on Runner’s World provides the following example of day or carbohydrate loading for a 150 pound runner:

Good Eats
A day of carbo-loading for a 150-pound runner

1 bagel with 2 tablespoons strawberry jam (71 g)
1 medium banana (27 g)
8 ounces fruit yogurt (41 g)
8 ounces orange juice (26 g)

2 Nature Valley Oats ‘n Honey
Granola Bars (29 g)
8 ounces Gatorade (14 g)

1 large baked potato with 1/4 cup salsa (69 g)
1 sourdough roll (40 g)
8 ounces chocolate milk (26 g)
1 large oatmeal cookie (56 g)

1 Clif Bar (42 g)
8 ounces Gatorade (14 g)

1 chicken burrito with rice, corn salsa, and black beans (105 g)
1 2-ounce bag Swedish Fish (51 g)


This is a bit more food than I expected.  Eating snacks of granola bars for both morning and afternoon snack is a good way to add in more carbohydrate calories.  I think this example really shows that you need to replace calories with carbohydrates more than you thought you would.

As a runner we spend many hours training, running, stretching and icing sore muscles or injured muscles.  We make it a priority to treat our bodies well, fuel ourselves and plan a race day outfit, and strategy.  It’s important to go the extra bit further and understand carbohydrate loading in the days leading up to a marathon or race.  It’s essential to help you perform well and finish strong. I encourage you to determine what your body needs in order to carb load correctly and give your body everything it needs to perform it’s best.

What are your favorite foods to carb load with?  Have you hit the wall? Have you not carb loaded correctly and paid the price? Have you had better races from carb loading correctly and bad races from doing it incorrectly?


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