Exercise and Diabetes. Sheri R. Colberg

Are DC’s actual reasons for not being more physically active the same as her stated ones?

      2. What would be the most effective way for DC to increase her physical activity level?

      3. What precautions (if any) would you recommend that DC take?

      4. What strategies will help motivate DC to be more regularly active?

      (Continued)

      HEALTH BENEFITS OF DAILY MOVEMENT (UNSTRUCTURED ACTIVITY)

      The health benefits of daily movement are numerous. For example, in sedentary men and women (without diabetes) undertaking either 6 months of fitness training or isocaloric pedometer-measured walking, their BMI, waist circumference, waist-to-hip ratio, and resting heart rate were reduced in both groups, and fasting glucose, glucose tolerance, and total cholesterol were similarly improved (Bell 2010). Thus, although supervised fitness training in previously sedentary adults produces greater improvements in their peak oxygen consumption and other fitness variables, many health-related variables improve similarly from a pedometer-based walking program matched for total energy cost.

      Daily movement apparently has a large impact on how well the body handles carbohydrate intake. In a recent study, healthy normally active adults cut their physical activity levels (as monitored with daily steps) from >10,000 a day to <5,000, which is considered a sedentary level (Mikus 2012), over a 3-day period. Despite the fact that they could still release extra insulin in response to a glucose load, their postprandial glucose spikes increased significantly and progressively over the 3 days, which reinforces the importance of daily physical activity as a mediator of glycemic control.

      For anyone with diabetes, inclusion of more daily, unstructured physical activity is likely to bestow similar, if not greater, health and glycemic benefits. Nonexercise activity thermogenesis (i.e., energy expended for activities of daily living) can create a large daily caloric deficit to prevent excessive weight gain, which can facilitate body weight and blood glucose management (Levine 2005, 2008). Simply standing counts as unstructured activity: in an observational study, obese individuals sat for ~2.5 h more and walked an average of 3.5 miles less per day than their lean counterparts. Moreover, most of the greater activity done by lean participants resulted from walks of short duration (<15 min) and low velocity (~1 mile/h) (Levine 2005). Health benefits result from concurrently reducing total time engaged in sedentary pursuits and interspersing frequent, short bouts of standing and physical activity between periods of sedentary activity, even in adults who are already physically active (Garber 2011, Dunstan 2012). Thus, how long individuals spend sitting each day and whether they move at all during periods of prolonged inactivity is critical to metabolic health and diabetes management.

      PROMOTING LIFESTYLE PHYSICAL ACTIVITY

      Engaging in frequent and daily physical activity is an essential part of self-care for all individuals with T2D. For anyone with type 1 diabetes (T1D), however, appropriate medication and dietary regimen changes likely will be needed to maintain control over blood glucose levels. All insulin users (regardless of type of diabetes) need to follow hypoglycemia prevention strategies. In many cases, the success of a physical activity should not simply be gauged by how much blood glucose levels decrease during participation. For insulin users, large drops in blood glucose are more likely to lead to rapid-onset hypoglycemia and worsened control. The focus instead should be on keeping the blood glucose level from interfering with the ability to continue the physical activity.

      Although physical activity of any type—including activities of daily living—is not guaranteed to improve acute blood glucose control in insulin users, it is still equally important for them. For instance, one study recently investigated the influence of computer use on glycemic control in 115 patients with T1D. Their A1C levels were not related to age, diabetes duration, television watching, or computer use, but rather were independently and negatively associated with the weekly hours that individuals spent doing any physical exercise (Benevento 2010). Table 3.1 gives some suggestions on how to get individuals started doing more daily physical movement.

      Table 3.1 Recommendations for Getting Started with More Daily Movement

      Following are some suggestions on how to get individuals with any type of diabetes more physically active on a daily basis:

      • Have them begin by focusing on more daily activities that are normal activities of daily living and involve physical movement of any sort, such as taking additional steps or standing longer each day.

      • Once individuals have established a solid base of greater daily movement, encourage participation in other physical activities like brisk walking, but make sure that they start at a low level and progress slowly to enhance compliance and reduce injury risk.

      • Have them include a variety of fitness activities to enhance differing aspects of their health. For example, yoga can reduce stress while improving overall health, well-being, and flexibility; aerobic activities like walking can help boost fitness levels; resistance and core exercises can lead to greater muscle strength; and ballroom or other dancing can improve balance, fitness, sense of enjoyment, and quality of life.

      • Help individuals find ways to decrease the total time that they spend doing sedentary activities, even simply by standing up while talking on the phone or by taking frequent breaks from sitting.

      • Encouraging individuals to move more and sit less will likely lead to their eventually incorporating activity with all types of goals.

       Breaking Up Sedentary Time

      Use of physical activity accelerometers has brought a better estimation of total daily movement, along with the time spent doing activities of varying intensities or nothing at all (like sitting or sleeping). In overweight and obese adults, interrupting sitting time with 2-min bouts of light- or moderate-intensity walking lowered their postprandial glucose and insulin levels (Dunstan 2012). Along the same lines, an individual would theoretically expend an additional 24, 59, or 132 kilocalories per day, on average, if he or she chose to stand up and walk around at a normal, self-selected pace for 1, 2, or 5 min every hour, respectively, compared with sitting continuously during an 8 h period (Swartz 2011). Making small changes like taking a 5-min walking break every hour could yield beneficial weight-control or weight-loss results.

      In adults with newly diagnosed T2D (ages 30–80 years), each hour of sedentary time during waking hours was associated with a larger waist circumference and lower levels of HDL-C, suggesting that a higher sedentary time is associated with a worse metabolic profile (Cooper 2012). Using similar techniques with accelerometer measurements, others have confirmed that the proportion of time spent in sedentary pursuits on a daily basis is strongly related to metabolic risk, independent of how much physical activity an individual otherwise does (Bankoski 2011). Thus, people with diabetes in particular may benefit from reducing their total sedentary time and avoiding prolonged periods of sedentary behavior, which they can do simply by increasing the number of breaks from sitting that they take during the day.

      Case in Point: Continued

      A health-care or fitness professional working with DC needs to discuss her personal beliefs, past experiences, preferences, and concerns about increasing her activity levels to figure out how to best assist her in becoming more active on a daily basis. Upon further discussion with DC, it becomes clear that her actual reasons for not exercising differed slightly from what she stated. She agrees that she lacks the motivation to exercise and that she feels too tired after work to do it then. She is also afraid of getting low blood glucose, however, because she takes insulin daily. Moreover, she does not feel safe walking in her neighborhood, especially in the dark during the winter, and she cannot afford to join a fitness center or buy expensive equipment to use at home.

      (Continued)

      KEEPING TRACK OF DAILY MOVEMENT

      One way individuals can keep track of how much daily movement they are doing is through the use of pedometers, which are small monitors that record the number of steps taken during the day. They have proven to be useful tools for increasing lifestyle physical activity because they provide immediate feedback, build confidence (in being active), and enhance enjoyment of