The American Diabetes Association (ADA) has issued consensus statement about physical activity, exercise, and type 2 diabetes in this month’s issue of Diabetes Care (June 2006). For too long, many people in the medical community, like so many people in general, have been lazy in their approach to physical activity and exercise. If we talked about exercise at all with patients, we were likely to say: “just walk a few blocks,” or “try walking thirty minutes three days a week”, or worse, “you should get some exercise.”With the explosion of type 2 diabetes worldwide, however, that lackadaisical approach to exercise should soon be changing.
Here is what an expert panel of the ADA, headed by Ronald Sigal, MD, from the University of Ottawa recommends:
- If you are prediabetic, in addition to a diet aimed at weight control, you should get at least 150 minutes per week of moderate (e.g., fast walking) to vigorous (e.g., jogging) physical activity per week. Diet and exercise have been shown to prevent the progression of prediabetes to full-blown diabetes. There is strong scientific evidence to support this recommendation.
- If you are diabetic or prediabetic and want to improve your blood glucose control, support weight maintenance, and reduce your risk of cardiovascular disease, the panel recommends 150 minutes/week of moderate-intensity aerobic physical activity. This is a physical activity that increases your heart rate to 50-70% of your maximum heart rate. This is not a stroll around the block. This is full-on fast walking. Wear a heart rate monitor or check your pulse to be sure you are achieving this level of aerobic exercise.
- Alternatively, you can perform 90 minutes per week of vigorous aerobic exercise. This is defined by achieving greater than 70% of your maximum heart rate. This, for many, will mean running, swimming, bicycling uphill, or a hard workout on the elliptical machine. Again, be sure you check your heart rate to see if you are really working out with vigor.
- Physical activity should be distributed over at least 3 days per week with no more than 2 consecutive days without physical activity.
The scientific evidence
Again, there is strong scientific evidence to support these recommendations.
- Although the evidence is somewhat less strong, the panel suggests that 4 or more hours a week of moderate to vigorous aerobic and/or resistance exercise is associated with greater cardiovascular risk reduction compared to lower volumes of activity.
- For long-term maintenance of major weight loss (e.g., 30 pounds or more), larger volumes of exercise (7 hours per week of moderate or vigorous aerobic physical activity) may be helpful. For all of you who are fans of People Magazine’s annual weight loss issue, take a look at the exercise histories of some of their long-time big losers. Many of these folks are now working in the fitness industry, working out several hours or more each day.
- Remember, weight loss and maintenance require careful attention to diet as well. Exercise alone, although it improves insulin sensitivity and burns calories, tends to produce only modest weight loss (about 4 pounds). It is easy to reward yourself with more food when you are exercising, thereby gaining instead of losing any weight.
- Unless they have medical reasons why they cannot lift weights, people with type 2 diabetes should be encouraged to perform resistance exercise at least 3 times a week, targeting all of the major muscle groups. The panel recommends three sets of 8-10 repetitions at a weight that cannot be lifted more than 8-10 times. Hey, guys, this last part is important. For most of us, that is not a 3-pound weight or even a 5-pound weight (my trainer laughs at these!). As you build strength and muscle, you most likely will have to increase the weight size to get to failing by the 8th or 10th lift. It is helpful to check in with a personal trainer periodically to be sure you are performing these exercises correctly and for maximal benefit.
Physicians have sometimes been reluctant to prescribe exercise for people with type 2 diabetes because of the known increased risk that these folks will have undiagnosed heart disease. Here is what the panel says about that:
- Before beginning a program of physical activity more vigorous than brisk walking, people with diabetes should see their health professional to assess whether they have any health reason that could cause problems with more vigorous physical activity. For example, is there a high risk of existing cardiovascular disease or are there diabetes complications, like nerve damage, that could predispose to injury or retinopathy (diabetic eye disease) that could cause get worse with vigorous activity.
- There are two websites that can be used to estimate risk. The UK Prospective Diabetes Study Risk Engine can be used to estimate ten-year cardiovascular risk. The American Diabetes Association’s Diabetes PHD can be used to estimate 30 year risk of a whole variety of clinical outcomes, including cardiovascular disease.
The panel also has the following recommendations about avoiding low blood glucose:
- If you take insulin or “insulin secretagogues,” such as an oral sulfonylurea, check your capillary blood glucose before exercise and about 2 hours after exercise. If your pre-exercise glucose is less than 100 mg/dl, you should consume some additional carbohydrates before, during, or after exercise. Note that if you are only treated with diet, metformin, alpha-glucosidase inhibitors, and/or thiazolidinediones (e.g., Actos or Avandia), extra carbohydrates are usually not necessary.
The take-home message. Don’t just assume, if you are diabetic, that you cannot or should not exercise. If your cardiovascular risk is low and you do not have diabetes complications, such as nerve or eye disease, physical activity can have many beneficial effects on your current and future health.