Exercise is key to prevention, control, survival with diabetes
Exercise is key to prevention, control, survival with diabetes
New studies show remarkable effects of this simple prescription
Exercise for health is almost as basic as you can get. For the vast majority of patients, however, exercise is an afterthought or not a factor in their lives at all, regardless of how often they are reminded of its importance.
Three groundbreaking new studies underscore the importance of getting patients with diabetes off the couch and into their walking shoes, onto their bicycles, or into the gym.
What would patients say if they were told that broad-based scientific evidence now shows moderate exercise routines can:
• prevent the onset of diabetes;
• help control diabetes more effectively;
• help patients stay alive longer?
The recently published studies show the vital importance of exercise throughout life for healthier living, says Ralph Hall, MD, emeritus professor of medicine at the University of Missouri-Kansas City School of Medicine.
Hall castigates health care professionals for not prescribing exercise as a matter of course and for failing to carefully instruct patients on how to exercise. "Just as with our failure to use drugs to reach the desired therapeutic goals, our failure to appropriately prescribe and monitor exercise for patients at risk for diabetes and those who already have diabetes falls far short of the goals that yield the maximum benefits for our patients."
What works best to keep patients with diabetes alive? "How well a person with diabetes does depends very much on exercise," says Paul Thompson, MD, past president of the Indianapolis-based American College of Sports Medicine. Thompson is cardiac director of preventive care at Hartford (CT) Hospital.
Adding moderate amounts of exercise to a patient’s daily routine has longer-lasting results than prescribing an intensive program that likely will fizzle out in a few weeks, say the experts.
Scare tactics and rigid routines have little effect, says Linda Haas, RN, PhC, CDE, past president for health care and education of the American Diabetes Association in Alexandria, VA, and a clinician at the Seattle VA Medical Center.
She recommends a practical approach. "Find out what the patient is willing to do and what the patient will tolerate." When patients begin to see results — improved insulin sensitivity, increased high-density lipoprotein cholesterol levels, and weight loss — "they will generally feel better and more motivated."
Most experts recommend cardiac stress tests for inactive diabetic patients before beginning an exercise program because there is a great deal of asymptomatic cardiovascular disease among this population.
Patients also should check their blood glucose levels before and after exercise so they can understand better how blood glucose responds to various types of exercise and intensity levels.
An ounce of prevention, not a gallon of sweat
Several studies have shown that people who lead physically active lives are less likely to develop Type 2 diabetes, but it has been difficult to pinpoint exactly how much exercise is needed to stave off insulin resistance.
Now, researchers at Harvard University in Cambridge, MA, think they’ve found the answer: Modest amounts of activity can have profound effects.
Analyzing data on 70,102 healthy women who participated in the Nurses Health Study beginning in 1986, they found that the most active women were 46% less likely to develop diabetes; compared with the least active women.1
During the eight years of the study, 1,419 women developed diabetes. After adjusting for age, smoking, alcohol use, history of hypertension, and history of high cholesterol, the study showed that the risk of developing diabetes fell as physical activity levels increased.
Women who exercised regularly had a 44% lower risk of developing diabetes, according to the data analysis. Those who were just somewhat active had a 25% reduction in risk of diabetes. Researchers measured exercise using MET (metabolic equivalent task) expenditures in hours. Women with zero to two MET hours a week were at the highest risk, and those with more than 21.7 MET hours were at the lowest risk.
What does it mean to be active?
"We have known for a long time that physical activity reduces the risk of diabetes and a whole range of other chronic diseases. But this study goes further to show that even moderate physical activity, like brisk walking, results in a major risk reduction that is well within the range of the average person," says epidemiologist Frank Hu, MD, PhD, of Harvard’s School of Public Health.
Realistic expectations of patients is key, says Hu. "We know that not everyone will go to the gym or play basketball, but something like walking can be incorporated into everyday life without major effort. People can get off the bus a stop or two early and walk the rest of the way home. They can park further from the office building. All of these things add up," he says.
Some women became more active during the eight years of the study — and for many, the result was improved health. Compared with women who were consistently sedentary, the women who were consistently active had a 41% lower risk of diabetes. Women who were sedentary when the study began but then became active had a 29% lower risk of developing diabetes.
Hu also noted that obese women seem to "self-select" into lower levels of physical activity, partly because of the difficulty in participating in physical activity, which may be responsible for the obesity-diabetes relationship. He also noted that losing fat during physical activity is more efficient and carries more potential health benefits because that is largely visceral fat, which is associated with a wide range of chronic diseases, rather than the less harmful subcutaneous fat.
"Physical activity is responsible for positive outcomes in a broad range of chronic disease, from heart disease to stroke to diabetes," says Hu, who published a similar study in the Journal of the American Medical Association in June showing similar positive results for ischemic stroke.1
"The message in this study is that some exercise is better than no exercise," says Hu. "However, like some drugs, there is a dose’ effect of exercise, too; a more vigorous lifestyle, in general, probably provides more protection against diabetes than just walking."
This study compares favorably with other analyses of the Nurses Health Study that show less strenuous exercise periods are as effective in preventing cardiovascular disease as intense workouts. In data derived from the Nurses Health Study, researchers found that women who walked for three hours a week at a pace of 20 minutes per mile reduced their risk of a heart attack by 30% to 40%. That reduction equals the same protection achieved by women who exercised vigorously for 1.5 hours a week.
Men and women should be as active as possible, says Hu. "If they don’t walk regularly, they should begin walking. If they are already walking, they should speed up. And if they are already walking briskly, they should try to engage in even more vigorous physical activity."
A life strategy of exercise has long been known to help control Type 2 diabetes. Now a Harvard researcher has unlocked the mechanism behind the health benefit.
Exercise increases the activity of a substance called AMP kinase (adenosine monophosphate-activated protein kinase), which may be a fuel gauge in the heart and other tissues signaling the need to turn on energy-generating metabolic pathways. In this case, AMP causes the muscle to take up and use more blood glucose, according to Laurie Goodyear, MD, assistant professor of Medicine at Harvard Medical School, who spoke to the American College of Sports Medicine in early June.
Researchers currently are searching for pharmaceutical ways to mimic the effects of exercise on AMP kinase in hopes of spurring muscles to draw more glucose from blood. But Goodyear notes there’s nothing quite as good for the body as a traditional workout and suggests an exercise program may be a way to keep patients with diabetes off oral medications for longer time periods. To be effective, exercise needs to be part of a prescribed regimen that includes diet changes.
She predicts a "worldwide explosion" of Type 2 diabetes, largely due to poor food choices and inactivity. Regular exercise could stave off this explosion by preventing insulin dysfunction in the first place.
Getting off the couch can save lives
Staying active translates to a longer life for a person with diabetes, according to researchers at the Cooper Institute for Aerobics Research in Dallas.
In the first study to find a lower risk of death from any cause among those who report they are physically active, lead researcher Ming Wei, MD, MPH, found that men who reported the least amount of physical activity were 2.1 times more likely to die of any cause than those who were physically active.
Wei, a clinical epidemiologist at Cooper, studied 1,263 men over 50 with Type 2 diabetes who underwent a baseline evaluation and treadmill test at Cooper between 1970 and 1993. Half the men reported they were not physically active at the outset of the study. They were instructed to report physical activity at regular intervals over an average of 12 years of follow-up.
The participants were asked to report their physical activity levels as well as answer questions on health habits, including current smoking status and dietary programs designed for weight loss or any other purpose.
At the outset of the study, 42% of the subjects were classified in the lowest fitness levels, and 58% were classified as "fit."
Over the period of the study, 180 men died, and those in the low-fit group were 2.1 times more likely to die than the high-fit group from any cause, including heart disease, a major killer of patients with diabetes.
Even more convincing, men who reported inactivity in their questionnaires were 70% more likely to die than those who reported being physically active.
Wei noted that his study shows the benefits of physical activity extend beyond its mediating effect on immediate risk factors, such as weight control.
While he doesn’t recommend any specific exercise regime, Wei says 30 minutes of moderate activity, such as a brisk walk, on most days, will bring patients into the "more-fit" category. "This gives us even more reasons to recommend exercise to our patients with diabetes," says Wei. "Specific exercise programs need to be prescribed, and follow-up is necessary."
"The bottom line is they will survive longer if they exercise," he adds.
| Suggested Activities | |
| Walking | |
| - easy pace — less than 3.2 km/hr | |
| - average pace — 3.2-4.8 km/hr | |
| - brisk pace — 4.8-6.2 km/hr | |
| - very brisk pace — more than 6.2 km/hr | |
| Other suggested activities for patients with higher fitness levels | |
| - jogging | |
| - bicycling | |
| - aerobic dance | |
| - rowing | |
| - lap swimming | |
| - squats | |
| - racquetball | |
| - tennis | |
| Source: Harvard School of Public Health, Cambridge, MA. | |
Reference
1. Hu F, Stampfer M, Colditz G, et al. Physical activity and risk of stroke in women. JAMA 2000; 283:2,951-2,967.
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