ABSTRACT
Diabetes and obesity have reached epidemic proportions throughout the world. The costs associated with quality of life and the toll on health-care systems is staggering. Type 1 diabetes results from loss of pancreatic beta cells and can occur early in life. Individuals with Type 1 diabetes require insulin injections to live. Type 2 diabetes generally occurs later in life, and obesity is a significant contributor to this type of diabetes. As visceral abdominal fat increases, low-grade inflammation results in many metabolically sensitive tissues, including adipocytes, liver, and muscle. Insulin resistance develops, as cells become less effective at taking up glucose. The resulting hyperglycemia leads to additional problems, including pancreatic beta cell dysfunction. Glucose intolerance develops, leading to Type 2 diabetes. Over time, chronic hyperglycemia can cause pancreatic beta cells to fail, and insulin replacement treatment becomes necessary.
Maintenance of blood glucose levels (euglycemia) is essential for good health. Insulin, glucagon, and several other hormones all play critical roles in the postabsorptive (fasting) and postprandial (fed) states. Lack of beta cell function and insulin can stress the normal homeostatic mechanisms, as can excessive intake of calories. Eating and drinking contributes the caloric energy; physical activity helps burn energy. When energy intake exceeds utilization, weight is gained. A healthy lifestyle plan should include a proper diet and exercise to help maintain a metabolically optimal weight. Exercise training can improve cardiovascular health significantly in individuals who are obese or prediabetic.
For individuals with diabetes, exercise requires additional attention to blood sugar levels. Hypoglycemia is the major concern, because if blood glucose levels get too low, the brain will shut down. Hyperglycemia is also a concern but is less critical in the short term. Prolonged bouts of hyperglycemia can induce diabetic ketoacidosis, which is also a medical emergency. Young people with Type 1 diabetes should be encouraged to participate fully in sports and physical activity; however, they need to monitor their blood glucose levels carefully, adjust their insulin and carbohydrate intake, and pay attention to the time of day. Exercise that includes high-intensity intervals and resistance training seems to minimize the chance for hypoglycemia. Interval and resistance training is also effective with people who have Type 2 diabetes. Low- to moderate-intensity exercise is good at improving HbA1c levels, which provide a measure of average glucose levels over the previous two to three months. High-intensity interval training and weight lifting improve insulin sensitivity. 269Maintenance of or increase in muscle mass is a desired outcome of training, as muscle contributes a significant amount of energy utilization, both when a person is working out and when at rest.
Insulin is on the WADA prohibited substance list. It has abuse potential because it has anabolic properties (it stimulates production of protein and other macromolecules) that enhance the effect of anabolic steroids. Drugs used to treat Type 2 diabetes are not prohibited, although related compounds not approved as drugs are on the banned list (GW1516 and AICAR).
