RESEARCH to PRACTICE
Exercise to Prevent and Treat Diabetes Mellitus
Brock A. Beamer, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 28 - NO. 10 - OCTOBER 2000
Diabetes mellitus is a large and growing health problem in the United States, and as such constitutes a target for many health initiatives. Exercise provides beneficial effects on excess weight, insulin resistance, and atherosclerosis, making it an important tool to mitigate diabetes symptoms and sequelae.
HP 2010, Diabetes Mellitus, and Exercise
Goal 5 of the Healthy People 2010 initiative states, "Through prevention programs, reduce the disease and economic burden of diabetes, and improve the quality of life for all persons who have or are at risk for diabetes." The need to increase physical activity is frequently mentioned in the text. Further, there are references to goals that seek to address related issues, including nutrition and overweight (19-1 through 19-3) and physical activity and fitness (22-1 through 22-15). These sections reflect a consensus view that exercise is an effective, inexpensive, safe, and noncontroversial means to treat (and in some cases prevent) diabetes.
This emphasis is most relevant for patients with type 2 diabetes, who constitute 90% of all cases. Exercise improves their most significant pathophysiologic defect, insulin resistance, and decreases their most prominent risk of death, cardiovascular disease (1-3). Patients with type 1 diabetes benefit as well, but their increased risk of hypoglycemia necessitates close coordination of their exercise and insulin regimens by a diabetes specialist (see reference 1 and www.diabetes.org for specifics).
What Does Exercise Do?
Exercise acutely lowers plasma glucose levels and tissue energy stores. More important, it improves insulin sensitivity and glycemic control, even without any weight loss. Of course, patients who have modest weight loss will have even greater improvement in these variables (1-3). Although most patients with diabetes will still require pharmacologic agents for adequate glycemic control, every regimen should emphasize diet modification and exercise. Since most patients with diabetes die from sequelae of vascular disease, exercise-induced improvements in blood pressure, lipid levels, and cardiopulmonary fitness are especially desirable. It may be that the greatest benefit to patients who exercise is reduced cardiac risk, rather than improved glycemic control.
"Filling" the exercise prescription. Unfortunately, most patients with diabetes are sedentary, deconditioned, and without experience in a structured exercise program (1,3). A great place to start is by having patients conscientiously increase their everyday activity, such as using stairs instead of elevators, walking a few extra yards, or doing a few minutes of housework. It may seem awkward at first, but actually writing prescriptions such as "park your car at least 100 yards from the entrance," will reinforce to patients how serious a matter activity is. From that starting point, a simple, easily managed plan of regular walking becomes less formidable (Rx: "Take three 10-minute walks every day").
Greater confidence in, and comfort with, an exercise regimen allows patients to increase intensity gradually, perhaps first to swimming or an aerobics class, then, if tolerated, to running or biking. (Be mindful, though, of the greater risk of injury to feet and joints with higher-impact exercises like step aerobics or running.) Maintaining and escalating such a regimen may require frequent, emphatic reminders of the benefits. Because the rewards of exercise for patients with diabetes—reduced long-term complications from hyperglycemia and hyperinsulinemia—are quite abstract, discussing the reduced risk of heart attack may be more motivational. Establishing short-term goals, such as improved exercise tolerance or modest weight loss, may help as well.
Risks and cautions. Most risks and complications of exercise for those with type 2 diabetes are similar to those for other middle-aged or older overweight individuals and are addressed elsewhere in this issue. Certainly, a screening history and physical exam to assess cardiac risk is warranted. Also, everyone should have a recent ophthalmic exam; those with proliferative retinopathy should avoid strenuous exercise or any resistance training (1).
The high prevalence of diabetic neuropathy and vascular insufficiency necessitates careful daily screening for foot wounds; even small blisters may lead to chronic wounds or cellulitis. Although exercise-induced hypoglycemia is relatively uncommon in those with type 2 diabetes, all involved should be able to recognize and treat it should it occur (1).
Despite widespread endorsement of exercise for diabetic patients, much remains unknown. How best can we motivate them to exercise? Which exercise is best? Aerobic training is firmly supported in the literature, but does increased muscle mass from resistance and strength training also improve insulin sensitivity? Similarly, how efficacious are low-impact activities? Should we place more emphasis on weight loss or on cardiopulmonary fitness?
Results from these active areas of investigation should enable us to individualize exercise regimens for maximal benefit to each patient. By motivating them to be more active, we will have many more healthy people in 2010.
Dr Beamer is an assistant professor in the division of geriatric medicine and gerontology at Johns Hopkins School of Medicine in Baltimore. Address correspondence to Brock A. Beamer, MD, Division of Geriatric Medicine and Gerontology, Johns Hopkins School of Medicine, 5505 Hopkins Bayview Cir, Baltimore, MD 21224; e-mail to [email protected].