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Finding the Right Balance of Insulin, Exercise and Carbohydrates

Diabetics hear it all the time: Exercise is good for you. And it's true. Except, well, when it isn't.

During or after exercise, many people with diabetes can experience hypoglycemia, also known as low blood sugar. To prevent that from happening, people with diabetes should learn to balance exercise with their intake of carbohydrates and their dosage of insulin, says Marian Marcella, a registered dietitian and a certified diabetes educator at the Northern California Diabetes Institute at Sequoia Hospital in Redwood City, California.

"When people want to begin an exercise program, we generally tell them to exercise after a meal," she says.

For people who want to lose weight, she says, taking less insulin with that meal is a solution that works for many people. The amount by which they should decrease the insulin will vary depending on the intensity of the activity, the time of day and other factors. For people not as concerned about losing weight, adding carbohydrates to their meal around the time of the exercise often can help prevent hypoglycemia.

Hypoglycemia is a dangerous and common side effect for many people with diabetes. The symptoms include dizziness, shakiness, sweating, headaches and other factors. Some people lose consciousness without having any of these symptoms.

The quickest way to deal with hypoglycemia is by raising your blood glucose with juice, candy or glucose tablets. But for people wanting to lose weight, adding more sugar to the diet isn't wise, Marcella says. That's why it's so important for people to understand their own relationship between exercising, eating carbohydrates and taking insulin.

Marcella and other diabetes experts advise that people starting an exercise program should test their blood sugar before and after the activity so they can learn how it reacts to exercise. And before starting any exercise program, she says, people should check with their doctor or other health care professional.

Exercise and other forms of physical activity — from walking the dog and taking the stairs instead of the elevator, to raking leaves and shoveling snow — can have benefits other than weight loss. Becoming active can increase your glucose uptake by increasing your metabolism and muscle mass, according to the American Diabetes Association.

Activity also can improve one's response to insulin, lessen the risk of heart disease and stroke, and help people with type 2 diabetes reduce their need for diabetes medications by lowering blood glucose levels.

Marlene Coates, a group fitness instructor and personal trainer, says exercise for people with diabetes should incorporate strength and fitness training, as well as adequate stretching. She also says that interval training — which includes shorter workout sessions than many other types of exercise — works well for many diabetics.

But that may not work for everyone; indeed, she says, no single type of exercise works for everyone.

"The best type of exercise," she says, "is the one you'll stick with."

Adapted by Editorial Staff, January, 2005
Last update, July 2008