The term insulin resistancemeans your dad's body is unable to respond to or use the hormone insulin in a normal, healthy way. Unlike a person with type 1 diabetes, your dad may well produce plenty of insulin, but for some unknown reason the insulin doesn't work very well at its job, which is letting glucose into the cells. Insulin resistance is the earliest indicator of type 2 diabetes and can be detected in people with diabetes before the condition is diagnosed.
Here's what happens: Your dad's body recognizes that it can't use the insulin it makes very well, so it starts to make more insulin to compensate for the resistance. But after years of such activity, the cells in the pancreas that produce insulin, called beta cells, can't keep up with demand. They wind up exhausted and are no longer able to produce all the insulin your dad needs. So in response, his blood sugar level rises. Typically, that's when someone like your dad gets diagnosed with diabetes.
Insulin resistance is more common in people who are overweight or obese, have hypertension or high levels of fat in the blood, or are sedentary. And, alas, among the elderly, insulin resistance increases with age -- even in people with diabetes who aren't particularly overweight or inactive, though it's not clear why this happens.
Left unchecked, insulin resistance allows high levels of insulin to circulate in your dad's blood. As a result, his blood vessels can become scarred and plaque can form, which causes narrowing of the blood vessels, making it more difficult for your father's blood to flow. This increases his risk of blockages in blood vessels, which can cause angina (severe chest pain) or a heart attack. People with insulin resistance are at three times greater risk for coronary artery disease than people who have normal insulin sensitivity.
Despite these potentially dire consequences, a number of treatments are available to treat insulin resistance. Losing weight, eating healthily, and getting active can all make a difference, as can a variety of prescription medications designed to target insulin resistance directly or treat related ailments, such as high blood pressure or elevated triglyceride levels. Ask your dad's diabetes educator and main diabetes doctor about what treatments could help him limit the impact of insulin resistance.