In prediabetes and Type 2 diabetes, on the other hand, the pancreas still produces insulin. However, two problems may be present. First, a person may experience insulin resistance, in which insulin becomes less effective at moving glucose from the blood into cells. And second, the pancreas may no longer make enough insulin to meet the body’s needs. When a person’s cells become resistant to the normal effects of insulin, the pancreas has to work harder to produce extra insulin in an effort to keep blood glucose levels in the normal range. Eventually, the pancreas can no longer keep up with the extra demand for insulin and blood glucose levels begin to rise.
Prediabetes and Type 2 diabetes usually develop over many years, with no, or only subtle, symptoms. Once diagnosed, however, prediabetes and Type 2 diabetes can often be controlled, if not completely reversed, through diet, exercise, weight loss, and oral medicines.
According to Gerald Reaven, an endocrinologist and professor at the Stanford University School of Medicine (and the author of several books, including Syndrome X: The Silent Killer), the overwhelming majority of people with Type 2 diabetes and prediabetes are insulin resistant. In addition, many children of people with Type 2 diabetes or prediabetes are insulin resistant themselves and therefore have an elevated risk of developing diabetes later in life.
Causes of insulin resistance
Although scientists don’t know the exact causes of insulin resistance, they are aware of several factors that promote it. These factors include obesity, an inactive or sedentary lifestyle, poor dietary habits, and family history (genes).
Obesity is a major cause of insulin resistance, but not all obese people are insulin resistant. Lean people can be insulin resistant, too, so it is clear that factors other than body weight matter. According to Dr. Philip Wood, a professor at Sanford-Burnham Medical Research Institute and author of How Fat Works, if you are overweight and have an apple shape (meaning your excess fat is stored in the abdominal region), you are more likely to develop insulin resistance than someone who is overweight and has a pear shape (with excess fat stored on the hips and thighs). Dr. Wood points out that regardless of body shape, weight loss can significantly lower insulin resistance and improve blood glucose levels in people with prediabetes or Type 2 diabetes.
Loss of muscle mass as a result of aging or inactivity may also lead to insulin resistance. According to Dr. Wood, loss of muscle is often associated with insulin resistance and elevated blood glucose levels in elderly people. In younger people, studies have shown that physical inactivity is as large a risk factor for developing insulin resistance as is being overweight or obese. Insulin resistance in sedentary people may be related to loss of muscle mass from inactivity, or it could result from something else entirely. Some studies suggest that inactive people with insulin resistance may not burn fat as well as those who have insulin resistance but are physically active and fit. Dr. Wood suggests that this reduced ability to burn fat for energy may contribute to the development of insulin resistance.
The amount and type of fat you eat may also play a role in insulin resistance. In a study of people from five countries, researchers found that people with diets high in saturated fat showed more insulin resistance than people who ate more monounsaturated fat. However, regardless of the type of fat, if the total amount of fat in the diet was high (more than 37% of total calories), so was the risk of developing insulin resistance. Researchers have also found a connection between insulin resistance and trans fat, which is found in foods that contain partially hydrogenated vegetable oils.