April 18, 2015

Insulin Resistance – Part 2

Type 2 diabetes is the type of diabetes that occurs later in life or with obesity at any age. Insulin resistance precedes the development of type 2 diabetes, sometimes by years. In individuals who will ultimately develop type 2 diabetes, it has been shown that blood glucose and insulin levels are normal for many years, until at some point in time, insulin resistance develops.

At this point, high insulin levels are often associated with central obesity, cholesterol abnormalities, and/or high blood pressure (hypertension). When these disease processes occur together, it is called the metabolic syndrome.

One action of insulin is to cause the body's cells (particularly the muscle and fat) to remove and use glucose from the blood. This is one way by which insulin controls the level of glucose in blood. Insulin has this effect on the cells by binding to insulin receptors on the surface of the cells. You can think of it as insulin "knocking on the doors" of muscle and fat cells. The cells hear the knock, open up, and let glucose in to be used. With insulin resistance, the muscles don't hear the knock (they are resistant). So, the pancreas is notified that it needs to make more insulin, which increases the level of insulin in the blood and causes a louder knock.

The resistance of the cells continues to increase over time. As long as the pancreas is able to produce enough insulin to overcome this resistance, blood glucose levels remain normal. When the pancreas can no longer produce enough insulin, the blood glucose levels begin to rise. Initially, this happens after meals, when glucose levels are at their highest and more insulin is needed, but eventually while fasting too (for example, upon waking in the morning). When blood sugar rises abnormally above certain levels, type 2 diabetes is present and can be diagnosed.

While the metabolic syndrome links insulin resistance with abdominal obesity, elevated cholesterol, and high blood pressure; several other medical conditions are specifically associated with insulin resistance. Insulin resistance may contribute to some of the conditions listed.
  1. Type 2 Diabetes
  2. Fatty liver disease
  3. Arteriosclerosis
  4. Skin Lesions
  • Acanthosis nigricans
  • Skin tags
  1. Reproductive abnormalities in women
  • Polycystic ovary syndrome (PCOS)
  • Hyperandrogenism
  1. Growth abnormalities
A doctor can identify individuals likely to have insulin resistance by taking a detailed history, performing a physical examination, and simple laboratory testing based on individual risk factors.

In general practice, the fasting blood glucose, A1c, and insulin levels are usually adequate to determine whether insulin resistance and/or diabetes are present. The exact insulin level for diagnosis varies by assay (by laboratory). However, a fasting insulin level above the upper quartile in a non-diabetic patient is considered abnormal.

Management of insulin resistance is accomplished through lifestyle changes such as diet, exercise, and disease prevention, and medications. Insulin resistance can be managed in two ways. First, the need for insulin can be reduced. Second, the sensitivity of cells to the action of insulin can be increased.

The need for insulin can be reduced by altering the diet, particularly the carbohydrates in the diet. Carbohydrates are absorbed into the body as they are broken up into their component sugars. Some carbohydrates break and absorb faster than others. These carbohydrates increase the blood glucose level more rapidly and require the secretion of more insulin to control the level of glucose in the blood. Since foods are rarely eaten in isolation, it can be argued that the glycemic index of each food is less important than the overall profile of the whole meal and associated drinks.

Several studies have confirmed that weight loss, and even aerobic exercise without weight loss, increase the rate at which glucose is taken from the blood by muscle cells as a result of improved sensitivity.

Over the past decade, insulin resistance has gained significance, in its own right, as a contributor to the metabolic syndrome. Timely intervention can delay the onset of overt type 2 diabetes. Future studies must assess longer intervals than research to date in order to determine the duration for treatment to prevent the development of type 2 diabetes and related complications.

Lifestyle changes in nutrition and physical activity are clearly important to delay the development of type 2 diabetes in individuals with insulin resistance and are the primary recommendation for prevention of diabetes in high-risk individuals. Metformin is the only drug recommended by guidelines, for those patients at highest risk. Education about these changes must be directed to all groups at risk for type 2 diabetes. Childhood obesity is epidemic and on the rise in the developed countries. Changes must be made in homes and school cafeterias to ensure healthier nutrition.

Please read this recent blog by Gretchen Becker on insulin resistance. Then read this blog by David Mendosa on insulin resistance and cocoa

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