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In the October 20 Journal of the American Medical Association (JAMA), Frank Hu, MD, of the Harvard School of Public Health, writes that people can cut the risk of type 2 diabetes nearly in half by engaging in one hour of moderate-intensity activity each day, which doesn't have to be all at once. This moderate-intensity activity can be accomplished with a walk to the bus stop in the morning, a walk up several flights of stairs in the afternoon, and housework in the evening.
"Clearly, you don't have to go to the gym and exercise furiously for an hour every day to cut your risk of developing diabetes," says Hu.
Walking Just as Beneficial as Running
A total of 70,102 female nurses, age 40 to 65 years, who did not have diabetes, cardiovascular disease or cancer, were evaluated starting in 1986. Approximately 47 percent of the women reported no vigorous activity and 60 percent of the women reported that they walked at least one hour per week. During eight years of follow-up, 1,419 women developed diabetes.
Hu says that those who increased their physical activity through walking lessened their risk for developing diabetes just as much as people who engaged in more vigorous forms of exercise like jogging, running and playing tennis.
"What is particularly interesting is that the risk reduction for moderate-intensity activity...is the same as that for more vigorous forms of activity...if the energy expenditure is the same."
Energy Expenditure is What Counts
Sheri Colberg, PhD, assistant professor of exercise science at Old Dominion University in Norfolk, Virginia, defines total energy expenditure as "the sum of all the energy that your body uses during the day."
Colberg says, "Any increase in total energy expenditure will result in a greater caloric need, which can be provided from fat stores." She points out that exercise makes it easier to achieve a balance between food intake and total energy expenditure, resulting in weight loss. "This will aid in the prevention or control of diabetes because insulin sensitivity improves with loss of excess fat weight."
Kris Berg, EdD, professor of exercise science and physical education at the University of Nebraska at Omaha, says it is still fine for people to run and work up a sweat. However, the JAMA study proved that high-intensity exercise may not be entirely necessary for the prevention of type 2 diabetes.
"It is pretty evident that the threshold and benefit of the exercise is best related to the total energy expended," says Berg.
Exercise Also Reduces Diabetes Risk in Men
Earlier this year, a similar study was published in the January 19 issue of the Annals of Internal Medicine, where researchers at the Cooper Institute for Aerobics Research in Dallas, found that inactive men face nearly four times the risk of developing diabetes compared with fit, physically active men.
During the 6-year study, investigators tracked 8,600 men over 30 years of age. They compared cardiorespiratory data to measurements of the men's fasting blood-sugar levels. The researchers reported that the least fit 20 percent of their subjects "had a 1.9-fold higher risk for impaired fasting glucose [a precursor to diabetes] and a 3.7-fold greater risk for diabetes" compared with the fittest 40 percent of men in the study group. Overall, 149 of the men in the study developed type 2 diabetes over the course of the study.
The researchers concluded that "a sedentary lifestyle may contribute to the progression from normal fasting glucose to impaired fasting glucose and diabetes."
Reversing Type 2 Diabetes With Exercise
Besides preventing type 2 diabetes, exercise has long been an important part of treating type 2 diabetes. After a type 2 diagnosis, some people have all but erased their type 2 condition by engaging in moderate-intensity activities.
Irwin Thall of Thousand Oaks, California, is 49 years old and has had type 2 diabetes for one year. He walks four miles per day on a treadmill, and on weekends he rides mountain bikes and hikes.
"Since starting this exercise program and following the diet plan laid out for me by my diabetes educator, I have lost 40 pounds," he says. "My HbA1c has gone from 10 to 4.7% and my average blood sugars are between 80 to 96 mg/dl, down from 256 mg/dl at diagnosis."
Bill Koile, 49, of Omaha, was diagnosed with type 2 diabetes this past February. He walks about 60 to 70 minutes a day, six days per week at a "brisk pace."
"My blood glucose is in the 95 to 140 range," Koile says, "and my HbA1c is 5.7%. I have lost about 65 pounds."
Any Activity Better Than No Activity
Colberg has always felt that any activity is better than no activity at all.
"Any use of muscle glycogen can stimulate insulin sensitivity," says Colberg, who agrees that one hour of walking, five days per week is sensible and beneficial. "Vigorous exercise will just have more of a long-lasting effect on insulin sensitivity. It is my feeling that the overall effect should be the same for all women, but younger women may need to walk at a faster pace in order to be working at a similar 'moderate pace.'"
Jack Amico, 54, of Buffalo, usually tries to incorporate some form of exercise into his everyday routine.
"I work on the second floor of an office building, and walk in and out of the building several times most days," says Amico. "I haven't taken the elevator in years. Instead, I take the stairs."
Amico says that his morning blood sugars run in the 105 to 110 mg/dl range and that his weight is coming off "very slowly." His HbA1c runs around 7 to 8%.
Colberg recommends that all individuals, diabetic or nondiabetic, start their exercise program sensibly and progress slowly, especially if they have not been exercising regularly.
"Overuse injuries (tendinitis, fractures) are more common when exercise starts out too intense or progresses too quickly, especially in individuals with diabetes," says Colberg. "Initial walking endurance may be low, so individuals can initially try walking three to four days per week for a minimum of 15 minutes at a time...As fitness increases, the speed of walking can be increased moderately as well."
Walking Hasn't Made a Difference For Me
Diane Bayliss, 58, of Brockville, Ontario, has had type 2 diabetes for three years. She has been a walker, however, for 20 years, walking three times per day, seven days per week for 40 to 50 minutes during each walk.
"I sometimes do a little running when feeling more energetic," she says.
Bayliss states, however, that walking has not had any effect on her weight, blood sugar control or HbA1c. In fact, since being diagnosed, she has put on 10 pounds.
"My HbA1c is 7% and has never been lower," she says. "It has been 9% but only once. I would like to achieve a 6%."
Berg argues that physical activity, despite being wonderful for diabetes control, is not a "panacea."
"There is a host of factors, besides body weight and levels of physical activity, that are going to make people prone to type 2 diabetes," he says. "Normally, physical activity like hers would protect people from becoming type 2 or would help them maintain their condition. But, each person is a unique individual."
30 Minutes a Day is More Realistic
Diane Pearson, RN, CDE, founder of Diabetes Care Consultants in San Diego, agrees with the findings of the JAMA study, but thinks that a more realistic goal for people with type 2 diabetes is 30 minutes per day, seven days per week.
"Exercise is a magical insulin-resistance breaker, and as far as we know, it is particularly helpful when there is accompanying weight loss, especially of overabundant abdominal fat," says Pearson. "I also agree that all things are equal in regard to 'time and energy' expenditure, regardless of the exercise being done."
Nadine Kiefer, 42, of Columbus, Georgia ("the capital of fried food and hot dogs"), walks for 30 minutes at a stretch on a treadmill. A bad back prevents her from engaging in more heavy-intensity exercise activities.
"I started out walking daily but found that I didn't have enough hours in the day for walking and my two young girls," says Kiefer. "I now walk three to four times per week."
Kiefer says that her treadmill routine has helped her to lose 5 pounds and her HbA1c has dropped from 9.8 to 6.8%. She used to take Glucotrol and Glucophage at the same time, but was able to stop taking Glucotrol during this process.
Kim Forrester, 42, of Sandy, Utah, gets her moderate-activity exercise by walking about 30 minutes per day, three to four times per week. She also takes a tap dance class for one hour each week.
"I have not noticed too much difference that walking has had on my blood sugar control, but at least I am able to maintain a level weight," says Forrester.
Study Supports CDC Guidelines
The findings of the JAMA study lend additional support to current guidelines from the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health recommending that Americans should accumulate at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week.
"It doesn't matter how you get the exercise," says Hu, "just that you get it."
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