Diabetes mellitus is a group of metabolic diseases characterized by high blood sugar or hyperglycemia. Chronic hyperglycemia results from defects in insulin secretion from the pancreas and/or insufficient insulin action in muscle and adipose tissue. Diabetes is characterized by both under- and over-secretion of insulin, the hormone that transports glucose across cell membranes. Diabetes is associated with long-term damage and dysfunction of the pancreas, eyes, kidneys, nerves, heart, and large and small blood vessels (American Diabetes Association [ADA], 2002a; Harris, 1995).
In type 1 or juvenile diabetes the insulin-producing beta cells of the pancreas are attacked by the individual's immune system resulting in a decrease in insulin production. Type 1 diabetes is designated as an autoimmune disease and accounts for approximately 5% of the cases of diabetes worldwide. Individuals with type 1 diabetes require insulin.
Type 2 diabetes or adult-onset diabetes is characterized by hyperinsulinism in response to the resistance of target tissues to the transport of glucose into cells. Obesity is a significant risk factor for type 2 diabetes. Type 2 diabetes accounts for approximately 90% of diabetes worldwide and is often considered a "disease of modernization" since it occurs disproportionately among populations adopting a Westernized lifestyle (Baschetti, 1998; Joe & Young, 1994; Popkin, 2001). It may be controlled through diet, exercise, and medication.
Approximately 5-10% of diabetes is due to other causes that are often transient rather than chronic.
These include gestational diabetes occurring during pregnancy (2-5%), drug or chemically induced diabetes, genetic syndromes, infections, and other endocrine diseases. A classification of diabetes lists more than 50 specific causes (ADA, 2002a; Centers for Disease Control, 2001).
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