Carbo-loading tips for Boston Marathoners

Posted on 14-04-2014 , by: Nancy Clark , in , 0 Comments

Without a doubt, what you eat and drink during the last few days and hours before the Boston Marathon makes a difference. By eating wisely and well, you can enjoy lasting energy without hitting the wall! Here are eight last minute carbo-loading tips for enhancing endurance.

1. Carbo-load, don’t fat-load.

Carbohydrate-rich foods include cereals, fruits, juices, breads, rice, plain baked potatoes and pasta with tomato sauce. Lower carbohydrate/higher fat choices include chips, cookies, buttery potatoes, ice cream, cheesy lasagna and pepperoni pizza. These carb-fat combinations may taste great and fill your stomach but they will not fill your muscles with glycogen (carbohydrate). Glycogen depletion is associated with running out of energy (hitting the wall).


2. No last minute hard training.

By exercising less the week before the marathon, your muscles will have the time they need to store carbohydrates and become fully carb-loaded. You can tell if your muscles are well carbo-loaded if you have gained a few pounds pre-event. That’s because your muscles store about three ounces of water along with each ounce of carbohydrate. (This water gets released and used during the event.)

3. No last minute dieting.

You can’t fully carbo-load your muscles if you are dieting and restricting your calories. You will have greater stamina and endurance if you are well fed, as compared to a dieting runner who may be a few pounds lighter but has poorly fueled muscles. Remember: you are supposed to gain (water) weight pre-event!

4. Drink extra fluids.

You can tell if you are drinking enough fluids by monitoring your urine. You should be urinating frequently (every 2 to 4 hours) the day before the marathon; the urine should be clear colored and significant in volume. (Stop drinking two hours before bedtime, so you can sleep through the night .. that is, if you are not too nervous to sleep!)

Juices are a good fluid choice because they provide not only water and carbohydrates but also nutritional benefits (Vitamin C, potassium). Save the sports drinks for during the event.

5. Eat tried-and-true foods.

If you drastically change your food choices when carbohydrate loading (such as eating several extra bananas), you may end up with intestinal distress. Simply eat a comfortable portion of the tried-and-true carbohydrates you’ve enjoyed during training. You need not stuff yourself! If you will be traveling to a far away event, plan ahead so you can maintain a familiar eating schedule despite a crazy travel schedule.

6. Eat a moderate amount of fiber.

If you stuff yourself with lots of white bread, bagels, crackers, pasta and other foods made with refined white flour, you may end up constipated. Include enough fiber to promote regular bowel movements––but not too much fiber or you’ll have the opposite problem! Moderate amounts of whole wheat bread, bran cereal, fruits and vegetables are generally good choices. (If you are concerned about diarrhea, limit your intake of these high fiber foods and instead consume more of the refined breads and pastas for one or two days pre-marathon.)

7. Eat breakfast on Marathon Morning.

You’ll need breakfast to maintain a normal blood sugar level. Although your muscles are well carbo-loaded from the pasta (and other grains, fruits and vegetables) you’ve eaten the past few days, your brain relies on the limited amount of sugar in your blood. When you nervously toss and turn the night before the event, you can deplete your blood sugar and, unless you eat breakfast before the marathon, you can start the event with low blood sugar. Your performance will go downhill from there…

Plan to replace the energy lost during the (sleepless) night with an early breakfast, as well as a pre-marathon snack at 9:00-10:30ish, as tolerated and depending on your start-time. You’ll have time to digest this food before the 10:00-11:30 a.m. Boston Marathon start. Stick with tried-and-true pre-exercise foods: oatmeal, cereal, bagel, toast, banana, energy bars and/or juice.

If you are afraid a pre-marathon breakfast will cause intestinal distress, eat extra food the night before. That is, eat your breakfast at 10:00 pm before you go to bed and then have a pre-marathon snack as tolerated that morning. Start drinking sports drinks early along the marathon route.

8. Consume carbs during the event.

During the Marathon, you’ll have greater stamina if you consume not only water, but also some carbohydrates. Depending on your body size and how hard you exercise, after the first hour of running (which is fueled by your breakfast), you should target about 200 to 350 calories/hour to avoid hitting the wall.

Slower runners may be better able to tolerate solid foods than faster runners. Hopefully, you have experimented during your long training runs so you know what works best for your body. Some popular choices include sports drinks, gels, defizzed cola, gummi candies, mints, chomps, chunks of energy bar, dried pineapple, and other easily chewed and digested foods. Your muscles welcome this food; it gets digested and used for fuel during the event so you can finish the marathon, perhaps with energy to spare!

For more information:

Nancy Clark’s Sports Nutrition Guidebook

Food Guide for Marathoners: Tips for Everyday Champions


Nancy Clark, MS, RD is a board-certified specialist in sports dietetics (CSSD). She counsels both casual and competitive athletes at her private practice located in Newton, MA (617-795-1875). Nancy Clark’s Sports Nutrition Guidebook and her Food Guide for Marathoners: Tips for Everyday Champions are available via

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