May 2014 Issue
Benefits of Physical Activity — Why Regular Exercise Is One of the Most Effective Tools in Diabetes Management
By Constance Brown-Riggs, MSEd, RD, CDE, CDN
Vol. 16 No. 5 P. 12
Clients and patients with diabetes hear about the importance of diet, nutrition, and meal plans all the time. Nutrition often is referred to as the cornerstone of diabetes control. But physical activity is just as beneficial for those who want to live well with the disease since regular exercise improves blood glucose control and has other health benefits.
When Jennifer Smith, RD, LD, CDE, was diagnosed with type 1 diabetes more than 25 years ago, one of the most beneficial recommendations she and her parents received from her pediatric endocrinologist was to stay active. Her physician emphasized how important daily movement is for diabetes management. Smith says that through the years, she’s continued to remember this recommendation.
As an adult, Smith continues to be active. In fact, several years ago, she began participating in triathlons. After several small sprint distance races, she realized she needed to revamp her routine during her races to maintain diabetes control for optimal performance. She attended a camp that catered specifically to athletes with diabetes.
As the director of lifestyle and nutrition at Integrated Diabetes Services in Wynnewood, Pennsylvania, Smith found her camp experience beneficial to herself and for the training and education of her clients with diabetes. Smith, who completed her first full marathon this past January, knows firsthand about the advantages of daily movement. “My blood glucose, along with other health measurements like cholesterol and blood pressure, remains most optimal when I move daily,” she says.
Exercise and Glucose Regulation
It’s common knowledge that regular physical activity improves blood glucose control, reduces cardiovascular risk factors, contributes to weight loss, and improves well-being.1 Most of physical activity’s benefits on blood glucose are the result of acute and long-term improvements in insulin action, accomplished with both aerobic exercise and resistance training.2
The acute impact of exercise on blood glucose depends on the intensity, duration, and timing of the activity. However, the familiarity of the exercise performed and associated stress hormones of exercise, such as adrenaline and norepinephrine, also impact glucose balance.
“Some forms of exercise, such as weight lifting or sprints, come with adrenaline production,” says exercise physiologist Gary Scheiner, MS, CDE, owner of Integrated Diabetes Services. “A lot of adrenaline at the same time as exercise will cause blood glucose levels to rise.”
In general, low- to moderate-intensity aerobic activities, such as walking or jogging, promote a decrease in blood glucose during the activity, while high-intensity aerobic or anaerobic activities, such as sprint running or sprint cycling, can cause a boost in blood glucose. Activities that combine some anaerobic and aerobic activities have been found to have the best effect on blood glucose levels.3 “For people with type 1 diabetes, physical activity is an effective tool to improve blood glucose after meals,” says Scheiner, who’s also the 2014 American Association of Diabetes Educators’ Diabetes Educator of the Year and author of Think Like a Pancreas.
In addition, there’s significant evidence on the other health benefits of regular exercise for those with type 1 diabetes, such as cardiovascular fitness, muscle strength, and improved insulin sensitivity. However, the literature has shown inconsistent effects on hemoglobin A1c results.1
“In type 2 diabetes, physical activity gets to the root cause of the problem, which is insulin resistance,” Scheiner says. “It helps to reverse what causes diabetes in the first place.” Physical activity increases insulin sensitivity, enhances uptake of blood glucose for glycogen synthesis, and stimulates fat oxidation and storage in muscle.2 According to a 2010 joint position statement issued by the American College of Sports Medicine and the American Diabetes Association, physical activity can result in acute improvements in systemic insulin action lasting from two to 72 hours.
Lipids, Blood Pressure, and Cardiovascular Risk
According to Scheiner, physical activity is “the most effective tool we have without side effects like medication,” and it also may be the most cost-effective approach for maintaining optimal lipid and blood pressure levels. This is important since heart disease is the leading cause of death in people with diabetes. Observational studies suggest that higher levels of physical activity are associated with lower cardiovascular risk and mortality.2
In the Look AHEAD (Action for Health in Diabetes) study, patients in the intensive lifestyle group experienced greater decreases in triglycerides and higher increases in HDL cholesterol than those in the control group, while both the intensive lifestyle and usual care groups saw decreases in LDL cholesterol.2 Most lifestyle intervention studies resulted in an approximate 5-kg weight loss (roughly 11 lbs).2
In general, the improvements in lipid profile appeared independent of changes in glycemic control and weight, and were more evident in those with a poor initial lipid profile.2 The American College of Sports Medicine 2010 guidelines state that combined weight loss and physical activity may be more effective in lowering lipids than aerobic exercise training alone.
Other research on individuals with type 2 diabetes suggests that aerobic training may slightly lower systolic blood pressure, but reductions in diastolic blood pressure are less common.2 Several randomized, controlled trials have shown decreases in systolic blood pressure of 4 to 8 mm Hg, but only one reported a slightly lower diastolic blood pressure.2
The Look AHEAD trial found reductions in both systolic and diastolic blood pressure with exercise and weight loss, but several studies have reported no changes in blood pressure with aerobic training in type 2 diabetes patients.2 Evidence that regular exercise improves blood pressure levels in type 1 diabetes is questionable, with some studies showing only a 2% to 3% reduction and others no effect.3
Recommendations and Risk
According to the American Diabetes Association’s 2014 standards of diabetes care, it’s reasonable to recommend that diabetes patients follow the same physical activity guidelines as the general population. “When you live with a chronic health condition, such as type 1 or type 2 diabetes, that can affect a lot of other parts of the body, the benefit of exercise becomes even more valuable,” Smith says.
Adults with diabetes should be encouraged to engage in moderate-intensity aerobic exercise at least 150 minutes per week at 50% to 70% of maximum heart rate. Physical activity should be spread out at least three days per week with no more than two consecutive days without exercise. In the absence of contraindications, adults with type 2 diabetes should do resistance training at least twice per week.1
While there are many benefits associated with physical activity, there are potential risks as well. Hypoglycemia and hyperglycemia are acute risks associated with exercise. Microvascular complications, such as retinopathy, and macrovascular complications, such as stroke, are long-term risks. Nutrition professionals who advise diabetes patients must understand these risks before making specific recommendations. “Someone with diabetes and Charcot foot will need different physical activity recommendations than someone who just needs to improve blood glucose levels,” Smith says.
The health benefits of physical activity for people with diabetes have been well established, but many with the disease don’t become or remain physically active. Smith offers the following tips to help nutrition professionals motivate clients and patients to exercise regularly and improve their health:
• Focus on the real reasons people want to improve their health. When you ask patients why they want to exercise and you hear “Because I know it’s good for me” or “Because my doctor told me I need to,” ask additional questions to uncover the real answers. They may want to dance at a daughter’s wedding, increase their energy during the day, travel, or be able to walk without fatigue. Once they give you specifics, you’ll have a goal to aim for.
• Show clients how to measure the benefits of exercise. Encourage patients to test their blood glucose before engaging in physical activity. Challenge them to walk for 10 to 20 minutes and test their blood sugar again to see how much it may have improved. When they observe the results, they’ll see how much impact physical activity has on blood glucose and be more inclined to exercise regularly. In addition, these values on their blood glucose monitor can help them see what does and doesn’t work in their blood glucose management.
• View physical activity as medicine. As Scheiner mentioned, exercise is like free medicine, and dietitians should tell clients that. Physical activity will bring blood glucose levels down and, if done regularly, can have an overlapping effect day to day.
The Bottom Line
Physical activity is as important as diet in type 1 and type 2 diabetes management. It improves blood sugar, reduces cardiovascular risk factors, and enhances well-being. However, clients and patients must engage in physical activity regularly to glean its continued benefits, so it’s important to remind clients that exercise is critical for optimal health. To be most effective, physical activity messages and interventions should be responsive to an individual’s readiness and willingness to change.
— Constance Brown-Riggs, MSEd, RD, CDE, CDN, is the nutrition advisor for the Dannon One Yogurt Every Day Initiative; the past national spokesperson for the Academy of Nutrition and Dietetics, specializing in African American nutrition; the author of the African American Guide to Living Well With Diabetes and Eating Soulfully and Healthfully With Diabetes.
1. American Diabetes Association. Standards of medical care in diabetes—2014. Diabetes Care. 2014;37(Suppl 1):S14-S80.
2. Colberg SR, Sigal RJ, Fernhall B, et al. Exercise and type 2 diabetes: the American College of Sports Medicine and the American Diabetes Association: joint position statement. Diabetes Care. 2010;33(12):e147-e167.
3. Colberg SR, Riddell MC. Physical activity: regulation of glucose metabolism, clinical management strategies, and weight control. In: Peters A, Laffel L, eds. American Diabetes Association/JDRF Type 1 Diabetes Sourcebook. Alexandria, VA: American Diabetes Association; 2013.