Prep for Greatness: Nutrition for Physical Training

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Whether you will be pounding the pavement up Heartbreak Hill this Monday or know an iron man competition is in your future, you need to think about how to best nourish your body. To ensure you have the energy and stamina to perform optimally in an endurance-type competition requires the proper amount and type of fuel. Like a race car in the Indy 500, regular grade gas just won’t cut it; you need premium octane.

It is reassuring to know that nutrition advice for people with diabetes who engage in vigorous, prolonged activity is the same as those without diabetes. To get your body in shape, a diet of low glycemic, non-processed carbohydrates, lean proteins, non-starchy vegetables, heart-healthy fats and low-fat dairy is in order.

During competitions of long duration, the body uses its aerobic (oxygen-using) muscle fibers which burn both fatty acids and carbohydrates from blood glucose and muscle glycogen. The more intense your effort the higher the volume of oxygen you will consume and the more glucose you burn. Hence, the greater the amount of carbohydrate you need.

You can become hypoglycemic if the ability of your liver to make glucose and maintain normal blood glucose levels is compromised and you don’t supply your body with adequate carbohydrate. You will find that you will be eating large quantities of carbohydrates to maintain your energy level.

Along with ensuring a sufficient source of carbohydrate, keeping hydrated is the most important nutritional priority. Dehydration during competitions, especially those occurring in warm climates, is a serious concern.

While you’re training, make sure you’re getting enough carbohydrate using a bit of simple math. First, convert your weight to kilograms (you can do this easily right in Google). For each kilogram of weight you should eat a certain amount of carbs, depending on how rigorous your training is. (These units are grams per kilogram of body weight, or g/kgbw.)

For moderate to vigorous training, you should eat 7 to 10 g/kgbw of carbs per day. Anything more intense than that, you should consume between 10 and 12 g/kgbw.

(Moderate physical activity is defined as activity requiring 3 to 5.9 times the exertion than you need to give when you’re at rest. Vigorous activity is greater than 6 times the exertion of rest. Generally brisk walking, dancing, biking on flat terrain are examples of moderate level activities.)

So for a 150 pound man, this translates to between 477 grams and 818 grams of carbohydrate per day, depending on the activity level.

Tips for the day of your event!

Pre-Exercise Meal

  • Eat 3 to 4 hours before the start of the competition
  • Choose low glycemic carbohydrates: whole grain high fiber choices such as whole grain crackers, breads, pastas, vegetables, fruits, along with lean proteins.
  • Drink between 17 to 20 ounces of water

During Exercise:

  • Consume 30 to 60 grams of carbohydrate at 30 to 60 minute intervals
  • Choose high glycemic carbohydrates such as crackers, sports drinks, gels, low fat, moderate protein sports bars. High glycemic choices are preferred because you want carbohydrates that are easily digested and can provide fuel quickly.
  • Drink 5 to 10 oz of water or sports drink every 15 to 20 minutes. Avoid using juice or soda as their high osmotic load (particle distribution) can increase the risk of gastrointestinal distress.


  • Snack within 30 minutes post exercise using high glycemic index carbohydrates and a small amount of lean protein
  • Aim for 1 to 1.5 grams of carbohydrate of moderate glycemic index per approximately 2 pounds of body weight and low fat protein at meals for the rest of the day. For example, a cup of chocolate milk, a piece of fruit, a turkey sandwich with lettuce and tomato.
  • Drink 16 to 24 oz of water or sports drinks for every pound you lost during the event.

In addition to the fuel and hydration issues all endurance athletes face, people with diabetes have to worry about keep their blood glucose in the safe zone. Either too low or too high and they won’t be able to give their best showing. And extremes of both conditions can be life threatening.

Every athlete is different and the amount of insulin to reduce and carbohydrate to eat will vary based on the day’s climate, your physical condition, your blood glucose control and the intensity and duration of the exercise. Exercise makes the body more sensitive to insulin and, in general, insulin doses need to be reduced for endurance competitions. But be careful—a severe dearth of circulating insulin can lead to the possibility of ketoacidosis.

Trial and error correction is the only true way of determining the right adjustments for you. Make sure you practice a number of times before your big event to make sure you get your doses right. Working with certified diabetes educator nutritionist and exercise physiologist can help you determine the best diet for your competition workouts.

And for all those starting the big race on Monday, good luck!

2 Responses to Prep for Greatness: Nutrition for Physical Training

  1. Josh says:

    This was an amazing post! I have been searching for a site to send to my parents who have begun biking recreationally doing 50 and 60 mile rides. I definitely plan to send this information on to them, and I plan to explore the rest of your blog to learn more. Thank you very much!

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