Type 2 diabetes mellitus, also known as adult-onset diabetes, is a common disease that interferes with the body's ability to store foods, resulting in high blood levels of sugar. Over time, high blood sugar levels can lead to such complications as blindness, kidney failure, and heart disease. Exercise helps to control blood sugar, lower blood pressure and cholesterol, and prevent weight gain. It is not known, however, whether physical fitness actually improves survival for patients with type 2 diabetes.