Physical Activity and Lifestyle Management

Physical activity

According to the American College of Sports Medicine (ACSM), every adult should accumulate at least 30 minutes of moderate-intensity physical activity on most or all days of the week in order to promote good health and prevent chronic disease.[1] In addition to the health benefits of physical activity,[2,3] people with diabetes can also experience diabetes-specific benefits of physical activity, including lowered A1C and reduced insulin requirements.[4] People with diabetes can exercise safely if the proper self-management strategies and the proper precautions are employed. Before beginning any exercise program, a thorough screening for cardiovascular disease, peripheral arterial disease, retinopathy, nephropathy, and neuropathy should be undertaken.[5] Adequate warm-up, stretching, and proper footwear are essential.[5]

Physical activity and type 1 diabetes

People with type 1 diabetes (in good metabolic control and without complications) can safely engage in all forms of physical activity, provided that they possess the necessary self-management skills. In order to safely engage in physical activity, it is necessary to monitor blood glucose levels frequently, to be aware of the physiological signs and symptoms that accompany hypoglycemia, and to be able to adjust insulin dose to account for physical activity.[5]

Because physical activity promotes peripheral glucose uptake, either a decrease in insulin dose or an increase in carbohydrate intake is necessary.[6] Because of weight gain concerns with insulin use, a decrease in insulin dose is the recommended method for addressing glycemic changes associated with planned physical activity. Unplanned activity requires an increase in carbohydrate intake to prevent hypoglycemia; 10 g to 15 g of carbohydrate per hour are required for moderate-intensity activity. More carbohydrate may need to be ingested for unplanned activity of longer duration or of higher intensity.

Physical activity should not be undertaken without adequate metabolic control. Activity should not be initiated if blood glucose levels are lower than 100 mg/dL or greater than 250 mg/dL with concomitant ketosis. It is important to note that the effect of physical activity on increased glucose utilization can be maintained for up to 48 hours,[7] so increased monitoring may be required following vigorous exercise in order to prevent delayed hypoglycemia. A full list of physical activity guidelines appears in Table 1.

Table 1. Physical activity and glycemic control[5]

Physical activity and type 2 diabetes

Type 2 diabetes is highly comorbid with obesity.[8] Although physical activity by itself is not an effective weight loss strategy, it is an important strategy for weight loss maintenance. Further, one study demonstrated that men with higher levels of cardiorespiratory fitness had a lower all-cause and cardiovascular mortality than did men with lower levels of cardiorespiratory fitness, regardless of their body composition.[9] Thus, physical activity is a critical part of any treatment plan for type 2 diabetes.

Because many people with type 2 diabetes are sedentary, physical activity promotion in this population has switched from an emphasis on structured aerobic activity to an emphasis on lifestyle physical activity. Lifestyle activity is defined as the daily accumulation of at least 30 minutes of self-selected activity, which can include leisure, occupational, or household activities.[10] Lifestyle activity interventions have demonstrated efficacy comparable to structured aerobic activity, and they have the benefit of being self-selected, thereby increasing motivation.[10]

Because the improvements in insulin tolerance and glucose sensitivity that accompany physical activity typically deteriorate within 72 hours,[11] regular activity is of great importance. According to the ACSM guidelines, people with type 2 diabetes should exercise at least 3 nonconsecutive days per week and should strive for at least 5 physical activity sessions per week.[12] In terms of intensity, low- to moderate intensity is recommended, as that is what is required to achieve favorable metabolic changes.[12] Physical activity sessions should start at 10 to 15 minutes, with the goal of increasing to 30 minutes.[12] Activities that offer greater control over intensity, have little interindividual variability in energy expenditure, are easily maintained, and require little skill are recommended.[12] A summary of the ACSM guidelines appears in Table 2.

Table 2. ACSM guidelines for exercise and type 2 diabetes[12]

Physical activity and the prevention of type 2 diabetes

Three major research trials have demonstrated that physical activity is a beneficial way to prevent or delay type 2 diabetes. The Da Qing IGT and Diabetes Study[12] was a large multicenter trial conducted in China in 1986. This study showed that either diet, exercise, or a combination of diet and exercise decreased the incidence of type 2 diabetes among people with impaired glucose tolerance. Similar findings were observed in the Finnish Diabetes Prevention Study,[13]which found that overweight participants with impaired glucose tolerance who participated in intensive lifestyle intervention reduced their risk of type 2 diabetes by 58%. In this study, the lifestyle intervention consisted of individualized counseling designed to help participants lose weight, decrease dietary fat intake, and increase dietary fiber intake and physical activity.

The results of these 2 studies were replicated in the Diabetes Prevention Program (DPP), a large multicenter study conducted in the US.[14] People with impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) who participated in a lifestyle intervention demonstrated a 58% reduction in type 2 diabetes compared with the placebo group. The lifestyle intervention consisted of a healthy low-fat diet and at least 150 minutes of physical activity (eg, brisk walking) per week. Based on the success of this study, the American Diabetes Association recommends at least 150 minutes/week of moderate-intensity aerobic activity and/or at least 90 minutes/week of vigorous activity.[15]

Conclusion

Physical activity is an important component of treatment for type 1 diabetes and type 2 diabetes, and for the prevention of type 2 diabetes. It increases peripheral glucose uptake, decreases insulin requirements, and is useful for the prevention of weight gain.

References

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2. Laaksonen DE, Atalay M, Niskanen LK, et al. Aerobic exercise and the lipid profile in type 1 diabetic men: a randomized controlled trial. Med Science Sports Exer. 2000;32:1541-1548.
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4. Beaser RS. Exercise. In: Beaser RS and the staff of the Joslin Diabetes Center, eds. Joslin's Diabetes Deskbook: A Guide for Primary Care Providers. Boston, MA: Joslin Diabetes Center; 2001:101-124.
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6. American Diabetes Association. Nutrition principles and recommendations in diabetes. Diabetes Care. 2004;27(suppl 1):S36-S46.
7. Sato Y, Iguchi A, Sakamoto N. Biochemical determination of training effects using insulin clamp technique. Horm Metab Res. 1984;16:483-486.
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10. Dunn AL, Andersen RE, Jakicic JM. Lifestyle physical activity interventions: history, short- and long-term effects, and recommendations. Am J Prev Med. 1998;15:398-412.
11. Albright A, Franz M, Hornsby G, Kriska A, et al. For the American College of Sports Medicine. Exercise and type 2 diabetes. Med Sci Sports Exer. 2000;32:1345-1360.
12. Pan XR, Li GW, Hu YH, et al. Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance: The Da Qing IGT and Diabetes Study. Diabetes Care. 1997;20:537-544.
13. Lindstrom J, Eriksson JG, Valle TT, et al. Prevention of diabetes mellitus in subjects with impaired glucose tolerance in the Finnish Diabetes Prevention Study: results from a randomized clinical trial. J Am Soc of Nephrol. 2003;14:S108-S113.
14. The Diabetes Prevention Program Research Group. Reduction in the incidence to type 2 diabetes with lifestyle intervention or metformin. New Engl J Med. 2002;346:393-403.
15. American Diabetes Association. Standards of medical care in diabetes-2006. Diabetes Care. 2006;29(suppl 1):S4-S42.