What Causes Diabetes?
There are two main kinds of diabetes, called Type 1 and Type 2. According to the American Diabetes Association, "two factors are important in both. You inherit a predisposition to the disease and then something in your environment triggers it."
To understand what happens you need some background. When you eat, food is digested into sugar, which is also called glucose. Glucose enters the bloodstream and travels to your cells for nutrition. When an organ called the pancreas senses the glucose in the blood, it releases a hormone called insulin. Insulin acts as a "key" that "unlocks" the cells to let the glucose enter. With both types of diabetes, this process is impaired. The glucose can't get into the cells so it stays in the blood and causes a high blood glucose level (BGL).
Type 1 occurs when the body's immune system kills the insulin producing cells in the pancreas. Because insulin is no longer made, cells can't be unlocked and the glucose can't enter. We don't understand the triggers well so we can't prevent Type 1.
Type 2 results from a condition called insulin resistance (IR). This makes it harder for insulin to unlock the cells so more of it is needed. IR gets worse over time, so the pancreas works increasingly harder and slowly wears out. By the time BGLs reach diabetic levels the pancreas has lost 60-80% of its capacity to produce insulin. The cells require more insulin, the pancreas can't keep up and glucose stays in the blood.
We don't know why IR occurs but we do know some things that are associated with it. These include ethnicity, family history, age and others that are beyond personal control. Many people think that being overweight and sedentary or eating too much sugar causes diabetes, but none of these are true. In fact, only about 1 in 7 overweight people ever become diabetic while many thin people do.
Weight, activity and diet are critical to managing the disease but they are not the underlying cause. Without IR you won't get Type 2 diabetes. And since you can't avoid insulin resistance you shouldn't be blamed for - or feel guilty about - having diabetes.