Type 2 Diabetes
When we eat, the body converts sugars and starches into glucose, a form of sugar that can be used as fuel by the cells. The pancreas releases insulin, a hormone that enables the glucose to be taken in by the cells. In people with type 2 diabetes, the pancreas either doesn’t produce enough insulin and/or the body is unable to effectively use the hormone. In either case, the cells are deprived of energy, despite high levels of glucose circulating in the blood.
The Centers for Disease Control and Prevention (CDC) estimates about 23.6 million Americans have diabetes. Roughly 90 to 95 percent of patients have type 2. Most patients are older adults who are overweight and sedentary. However, doctors are seeing an increasing number of type 2 diabetes cases in children who are obese and don’t get enough exercise.
Over time, high levels of blood glucose damage the walls of the arteries and tissues. Adults with diabetes are two to four times more likely to die of heart disease or have a stroke than people without diabetes. Diabetes also increases the risk for high blood pressure, kidney disease, blindness, nerve disease, gum disease, slowed healing times and amputations. The CDC reports the cost of diabetes to the U.S. in 2007 was $174 billion.
The Role of Exercise
Many people with type 2 diabetes can control the disease through weight loss, diet changes and lifestyle changes. Physical activity is a key component of lifestyle change. In addition to helping a patient lose weight, exercise leads to a reduction in body fat, blood pressure and insulin resistance. Researchers report a one percent decrease in hemoglobin A1c levels (a marker of long-term glucose control) is associated with a 15 to 20 percent reduction in risk for cardiovascular complications and a 37 percent reduction in microvascular complications (like eye, kidney and nerve disease).
While experts agree on the importance of exercise, there is less agreement on which type of exercise will most benefit people with type 2 diabetes. The “Health Benefits of Aerobic and Resistance Training in Individuals with Type 2 Diabetes” (HART-D) study aims to find an answer. The study will follow about 360 men and women with type 2 diabetes who have a sedentary lifestyle. Roughly 100 of the participants are randomly assigned to an aerobics only (walking) program. Another 100 are assigned to resistance exercise (weight lifting) only group. A third group of 100 perform a combination of aerobics and resistance exercises. The remaining 60 participants are assigned to a stretching and relaxation group. The goal is to determine which exercise has the most impact on A1c levels.
Tim Church, M.D., Ph.D., Exercise Researcher with Pennington Biomedical Research Center in Baton Rouge, LA, says other studies have provided conflicting results on the benefits of different types of exercise for type 2 diabetes. In addition, study participants are typically left on their own to perform (or not to perform) the prescribed exercises. In the HART-D study, all study exercises take place at the research site, so doctors can monitor the activity levels.
Church says skeletal muscles use a significant amount of glucose. So, the researches are also doing muscle biopsies in a select group of participants to determine how the exercises affect skeletal muscles.
For general information on diabetes:
American Diabetes Association, http://www.diabetes.org
Centers for Disease Control and Prevention, http://www.cdc.gov/diabetes
National Institute of Diabetes and Digestive and Kidney Diseases, http://www.niddk.nih.gov
Bweir, Salameh, et al., “Resistance Exercise Training Lowers HbA1c more than Aerobic Training in Adults with Type 2 Diabetes,” Diabetology and Metabolic Syndrome, December 10, 2009, Vol. 1, No. 27.
Marcus, Robin, et al., “Comparison of Combined Aerobic and High-Force Eccentric Resistance Exercise with Aerobic Exercise Only for People with Type 2 Diabetes Mellitus,” Physical Therapy, November 2008, Vol. 88, No. 11, pp. 1345-1354.
Plotnikoff, Ronald, et al., “Alberta Diabetes and Physical Activity Trial (ADAPT),” Trials, January 12, 2010, Vol. 11, No. 4.
Sigal, Ronald, M.D., et al., “Effects of Aerobic Training, Resistance Training, or Both on Glycemic Control in Type 2 Diabetes,” Annals of Internal Medicine, September 18, 2007, Vol. 147, No. 6, pp. 357-369.