Fueling For the Marathon: Final Preparations


By Dr. Karen Reznik Dolins, EdD, RD, CSSD, CDN

published in Body Local

You’ve done all the long runs and are now enjoying the taper running fewer miles so your body is strong on the big day.  What else can you do to enhance your performance?  Make sure your fuel tanks are full!

Sugar (glucose) and fats are the fuels your muscles will be using on race day. The more intense your run, the more glucose your muscles will use and the faster your muscles will use it up. Low glycogen stores forces you to slow down your pace and makes the run feel harder.  Your muscles will run dry at which point you will “hit the wall” or “bonk.”  Whatever you call it, this when each step takes so much effort that you start to think of quitting.

All endurance athletes run the risk of bonking because while we store plenty of fat, sugars are in limited supply. You can avoid bonking by taking two important steps: carbohydrate loading, or packing your muscle and liver stores with glucose, and supplementing sugar during the run.

Training changes the body’s physiology in a number of ways. Blood volume increases which allows the heart to pump more blood with each beat. This delivers more oxygen and fuels to muscle cells. Trained athletes also produce more mitochondria, the powerhouse of the cell where sugars and fats are converted into useable energy. After eating a meal with carbohydrate (fruits, vegetables, starches, milk, yogurt, sugar)  some gets stashed in the liver in the form of glycogen.  If you exercised before eating, glycogen will also be deposited in your muscles. Marathon training, stimulates muscle to store more glycogen, creating a larger fuel supply.

Carbohydrate loading is based on the premise that depleting stores and providing carbs will stimulate muscle to pack in even more glycogen than training allows. In traditional carbohydrate loading, muscles were depleted by running for several days while eating a low carbohydrate diet. In the last 2-3 days before the race, running was minimized and carbohydrate foods were maximized. This works but is not always comfortable for the athlete. Fortunately, more recent research has shown that you can deplete your glycogen stores with one high-intensity workout, and pack your muscles full of glycogen by eating a high-carb diet for the next 24 hours; Muscles get as pumped up with glycogen as they did under the original method.

The amount of carbohydrates needed to accomplish loading is based on body weight, as this approximates the amount of muscle you have to store glycogen in. The recommended amount is about 10 grams of carbohydrate for every kilogram you weigh (weight in pounds/2.2=kilograms). Women seem to be able to maximize their glycogen stores with less, about 7-8 grams carbohydrate per kilogram body weight.  As an example, a 150 pound male runner would need about 680 grams of carbohydrate, while a 125 pound female runner would need about 450 grams.


150 lb. male runner = 68 kg x 10 = 680 grams of carbohydrate

125 lb. female runner = 57 kg x 8 = 454 grams carbohydrate

Once you’ve successfully carbohydrate loaded your muscles, you still need to provide a readily available supply during the race. Having carbohydrates in the form of sugar during the race will give you more energy and let you go farther before feeling tired; Downing a sports drink or other source of sugar  affects [?] neurotransmitters in the brain which signal fatigue. Ideally, take 60-90 grams every hour to maximize this effect (32-40 ounces of Gatorade or other sports drink). Getting your carbs from sports drinks has the additional benefit of providing fluids. If you prefer to use gels, be sure to drink 12 ounces of water for every 25 gram gel pack as the sugar alone will draw fluids away from your cells and into your gut, which can lead to dehydration and the runs.

So during your final preparations for the marathon, focus on filling up your fuel cells by eating mostly grains, cereals, fruit, vegetables, yogurt and milk.  No more than ¼ of your plate should be meat, chicken or fish.  This is plenty to ensure that you’re meeting your need for protein, but not so much that protein is taking the place of carbohydrate.  The following sample menus will give you an idea of what this would look like.

Rest up, fuel up, and enjoy the race!

Sample menu for female athlete


2 cups cereal (ie. Honey Nut Cheerios)

1 cup low fat milk

8 oz Orange juice


Large banana with 8 oz. yogurt


Turkey sandwich (3 oz) on whole wheat bun w/ lettuce, tomato, mustard (OR grilled vegetable sandwich on bun with 3 slices mozzarella cheese)

¼ cup raisins with 12 almonds



5 pretzel rods (salted)

1 large apple

Dinner (6pm)

2 cups whole grain pasta

½ cup tomato sauce

1 cup steamed broccoli

½ cup chick peas or grilled chicken breast


Cereal with low fat milk


Sample menu for male athlete


Large bagel with butter and jam

2 cups orange juice

8 ounces vanilla yogurt

2 cups Cheerios with milk

1 large banana


1 cup granola


Turkey sandwich on roll

2 cups chocolate milk

2 apples


¼ cup raisins

¼ cup nuts


6 ounces chicken

Large baked potato

Salad with dressing


2 cookies

1 cup low fat milk


4 Fig bar cookies

2 cups juice


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