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What you eat impacts how you run

If you’ve signed up for a half marathon, you’re about to take on perhaps one of the most difficult and rewarding physical challenges you’ve ever faced. 

First and foremost, start with a proper training plan. Following an established plan that helps you build up to 13.1 miles over time will help you get you closer to your goal. 

But exercise is only part of the equation. What you do in the kitchen is another part. Like fuel in a car, your diet influences your body’s performance. Quality fuel can lead to better training, which leads to better performance on race day.

“When you’re running a half marathon, you could be out there for more than two hours,” explained Dr. Callista Morris, an orthopaedic surgeon specializing in sports medicine. “You can’t run on empty—you need to make sure you properly fuel your body not only ahead of time, but also during and after every run. This means following a diet designed to help you do your best.”

Here’s a guide to fueling for your first half marathon.

Three months before the race
Whether it’s your first half marathon or your fifth, you should start preparing for the race about three months in advance. Take some time to map out your workouts and dietary changes from now until race day. Now is the time to ensure you’re eating enough calories to fuel progressively longer runs. 

“Three months before the race, start with small dietary changes,” said Dr. Morris. “Make sure you’re eating enough food throughout the day, and make sure you’re getting enough vitamins and nutrients. If you’re on a fad diet, trade it in for a standard, healthy diet full of lean protein, whole grains and plenty of fruits and vegetables.”

While you do need more calories when you’re training for a half marathon, you don’t need to go crazy with eating. Generally, you should add an extra 200 to 300 calories per hour that you work out. Try to get these calories from lean proteins, fruits, vegetables and whole grains. 

One month before the race
With just one month to go, you should now be running anywhere from 15 to 25 miles per week. It’s vital to make sure you’re focusing on complex carbohydrates.

“Complex carbohydrates are foods that are slowly converted into sugar in the body,” said Dr. Morris. “Foods like pasta, whole grains, beans, lentils and potatoes are all examples of complex carbohydrates.”

Complex carbohydrates are the best source of energy for a workout because they offer sustained energy rather than a quick burst of energy followed by a crash.

Try to eat complex carbs at least two hours before a workout. After working out, eat a meal with complex carbs and a serving of protein to help rebuild your muscles.

Several weeks before the race it’s also important to create your pre-run fuel routine. Now’s the time to figure out whether whole grain toast with nut butter agrees with your stomach, for example.  

Two weeks before the race
In the two weeks before the race, you should begin eating more complex carbs than you were previously. This means eating meals like oatmeal for breakfast, potato-based dishes for lunch and pasta for dinner. 

Throughout these two weeks, you can start sacrificing otherwise-healthy foods in favor of complex carbs. Start tapering off your leafy green vegetable intake, as they can be hard on your stomach during a run. 

At the end of the two weeks, you may notice that you’ve gained some weight. Don’t be alarmed; this is totally normal. This means your body is storing the carbohydrate energy, known as glycogen, in the liver and the muscles. During the race, your body will pull from this energy to help you finish strong.

Two days before the race
While many people are tempted to eat a big meal the night before the race, this isn’t a good strategy. Overeating can cause stomach pains and cause you to slow down during the race.

Eat your last big meal 48 hours before the race. This allows your body enough time to digest and store glycogen.

Once you reach 18 hours before the race, start to decrease the size of your meals. Lunch the day before the race should be your last normal-sized meal.

Day of the race
On the day of the race, practice your pre-run fuel routine by eating a small meal of carbs, like a banana with oatmeal or a bagel. Now is not the time to experiment with an unfamiliar food. 

During the race, focus on staying hydrated and balancing your carbohydrate and electrolyte needs. Drink water along the race route at about the same rate you did during training and try to avoid drinking too much. In addition, small, simple carbohydrates like gels can help you maintain the energy you need to push through and finish strong. 

Callista Morris, DO, is a fellowship-trained orthopaedic surgeon specializing in sports medicine. Dr. Morris sees patients at Geisinger’s Woodbine Lane clinic in Danville and Susquehanna University clinic in Selinsgrove. To make an appointment with Dr. Morris or another Geisinger sports medicine specialist, please call 800-275-6401 or visit
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