Volume 3, Number 2: Summer Solstice, 2001

Exercise as an Important Part of Type 2 Diabetic Therapy - BC Endocrine Research Foundation

Darcye Cuff

Healthy Heart Program St. Paul's Hospital, Vancouver, B.C.

Care and Management of Type 2 Diabetes

We’ve known for over sixty years that the three cornerstones of diabetes management are proper diet, appropriate medication and sufficient exercise. The primary goal of treatment, using these core elements, is to achieve the best possible regulation of blood glucose and to delay or prevent the complications common to diabetes. Much attention has been paid to diet and medication, but exercise has rarely received its proper place in this triad.

Insulin Resistance: The Underlying Feature of Type 2 Diabetes

Most Type 2 diabetics produce insulin, yet suffer from a peripheral (i.e. in the muscle, liver, and fat) defect in insulin action, termed insulin resistance. Insulin resistance is a universal feature of Type 2 diabetes and is responsible for hyperglycemia (high blood sugar). Insulin resistance is linked not only with hyperglycemia, but also with an increased prevalence of high blood pressure and high blood lipids (fats/cholesterol) and contributes to the progression of cardiovascular and peripheral vascular disease. Thus insulin resistance is closely linked with not only blood glucose control, but also with cardiovascular disease. Cardiovascular disease is particularly prevalent in people with diabetes, occuring two to four times as frequently (compared to those without diabetes) and is the leading cause of death. Therefore, a primary strategy for managing Type 2 diabetes is to improve insulin action – to decrease the insulin resistant characteristic of our peripheral tissue.

Lifestyle features, including exercise, can target the underlying problem of insulin resistance. Regular exercise favourably modifies insulin action and decreases insulin resistance, improving blood glucose levels. Exercise also is very effective in weight/fat loss, in lowering blood cholesterol and blood pressure, contributing to the lowering of cardiovascular risk.

What Type of Exercise is Most Beneficial?

Moderate intensity aerobic exercise three to six times a week, lasting 40-60 minutes per session, has proven helpful in improving insulin action and glucose control in Type 2 diabetics. Therefore this is the type of exercise program most often recommended to people with diabetes. What is not currently included in exercise recommendations is a light to moderate strength training program, as its role in diabetes therapy is not well studied. Strength training has been proven to play an important role in many other aspects of health, including bone health, prevention of falls, and prolonged independent living.

Strength training may be a type of exercise that has extra benefit for type 2 diabetes if added to an ongoing aerobic program. As we age and become less active, we lose our muscle mass (10% per decade) and gain fat mass. Muscle is our largest insulin-sensitive tissue and our response to insulin is related directly to the amount of muscle mass, and inversely related to the amount of fat mass. Both increasing muscle and decreasing fat will aid efforts to improve blood glucose control. Many scientists have documented the beneficial effects of fat loss, with and without exercise, on insulin resistance, but little is known about the role of muscle gain (or regain) on insulin resistance. Strength training is an exercise modality that specifically targets muscle mass, and may prove a useful tool in helping those with diabetes get the most out of their exercise program.

Investigating the Role of Strength Training in Therapy for Type 2 Diabetes

An ongoing study at the Healthy Heart Program of St. Paul’s Hospital is testing the role of strength training in improving insulin resistance. Women with Type 2 diabetes were recruited and randomized into three different groups; one which continues their usual diabetes program (without exercise?, the second which participates in a moderate aerobic exercise program, and a third which participates in a moderate aerobic exercise plus strength training. All three groups will be evaluated before and after a four month period for insulin sensitivity and body fat and body muscle composition.

We anticipate that the aerobic exercise group will have improved insulin sensitivity and improved body fat and muscle composition (i.e. less body fat, and the same or more muscle) versus those who continued their usual diabetes program (ie. little to no exercise). The third group, which participated in aerobic plus strength training, may prove to have an additional increase in muscle mass, and an additional increase in insulin sensitivity. If this proves to be the case, strength training could be a valuable addition to the exercise program of women with type 2 diabetes.

Darcy Cuff is an exercise specialist in the healthy heart program at St. Paul’s Hospital and a PhD candidate in the School of Human Kinetics at UBC.

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