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Exercising Toward Diabetes Control

More than 14 million Americans have type 2 diabetes, a condition characterized by poor control of blood sugar, or glucose (the body's principal source of energy). Type 2 diabetes usually appears after age 40. However, more people are developing the condition at an early age, and its overall incidence is rising. A major culprit is excess weight due to inactivity and a poor diet. Being overweight may impair the body's response to insulin, the hormone that regulates glucose metabolism. Excess weight also taxes the heart, which is adversely affected by diabetes.

Thus, exercise and a healthy diet are the first treatments recommended for type 2 diabetes. Regular exercise can decrease blood glucose levels and increase the body's sensitivity to insulin. Exercise also protects the heart by reducing blood pressure and triglyceride levels (a type of blood fat, or lipid). Improved blood glucose levels can delay or reduce the need for glucose-control medications and prevent diabetes-related complications, such as heart and kidney disease, diabetic retinopathy (damage to the light-sensitive portion of the eye), and diabetic peripheral neuropathy (degeneration of nerves serving the legs and arms).

Yet few people with diabetes meet the U.S. Surgeon General's minimum exercise recommendations for all adults: some combination of activities such as walking, jogging, swimming, and active chores (such as mowing the lawn or vacuuming) for at least 30 minutes almost every day. In fact, one recent survey of diabetes patients found that the majority of respondents did not exercise at all. Exercise is beneficial for virtually everyone with diabetes. However, special precautions are necessary, especially for people who require certain glucose-control medications and those with peripheral neuropathy.

Potential Compl

Exercise increases vulnerability to two major diabetes-related problems: hypoglycemia (a precipitous drop in blood glucose) and foot sores. Hypoglycemia is initially characterized by sweating, hunger, dizziness, anxiety, a rapid heart rate, and tremor. Without proper attention, the sufferer may lose consciousness and go into shock. Foot sores that are not properly treated can rapidly worsen, sometimes within a matter of hours, and lead to infection. Severe cases may require amputation.

Hypoglycemia is more common in patients who require insulin or sulfonylurea medications such as glimepiride (Amaryl), glipizide (Glucotrol), and glyburide (DiaBeta, Micronase). Those on newer diabetes medications—such as metformin (Glucophage), rosiglitazone (Avandia), or pioglitazone (Actos)—are less susceptible to the problem. The risk of foot sores is greater in people with peripheral neuropathy, which decreases sensitivity to foot pain. Poor circulation to the extremities, which impairs healing, often compounds the problem.

Other exercise-induced complications include dehydration and ketoacidosis (the buildup of waste products from fat metabolism), and possibly retinal detachment. Dehydration may develop during prolonged workouts because of excessively high glucose levels (hyperglycemia) when diabetes is poorly controlled. A serious condition, ketoacidosis is primarily a concern for people with type 1 diabetes, which usually develops in youth and always requires insulin. Some experts caution that retinal detachment may be a risk when those with advanced retinopathy perform activities that require bursts of strength. However, the data are unclear.

A Safe Routine

With proper planning, most diabetes patients can exercise as much as they wish. "Become familiar with how your blood glucose responds to various forms of exercise by assessing your blood glucose before and after exercise, and every half hour during workouts, and work with your health care team to adjust your medical and exercise regimens accordingly," advises Dr. Joel Braunstein, a Johns Hopkins cardiology fellow with a special interest in diabetes.

Some standard practices prior to exercising will help your routine go smoothly. One to two hours before working out, have a meal and about a pint of water. Just before exercising, check your blood glucose. If it is below 100 mg/dL, have a snack containing 15 to 30 g of carbohydrates. If it is more than 250 mg/dL (for type 2 diabetes) or 200 mg/dL (for type 1 diabetes), postpone exercising until the level declines. It's also important to drink 8 to 16 oz of water every 30 minutes during your workout and to replenish spent glucose with a post-exercise snack. Prolonged workouts may require more frequent monitoring and brief breaks for snacks and water. If you experience hypoglycemic symptoms during your routine, rest and have a snack or some juice.

People with advanced diabetic neuropathy should choose low-impact activities like swimming and cycling rather than high-impact ones like jogging. Everyone with diabetes, and especially those with peripheral neuropathy, should also inspect the feet for signs of irritation before and after exercise. For strength training, people with diabetic retinopathy should use light weights and multiple repetitions as a precaution. People with uncontrolled diabetes should not exercise until their blood glucose levels stabilize and they meet the goals they establish with their doctors.


From The Johns Hopkins Medical Letter: Health After 50, August 2000.


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