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.
- Type 2 Diabetes
- Fatty liver disease
- Arteriosclerosis
- Skin Lesions
- Acanthosis nigricans
- Skin tags
- Reproductive abnormalities in women
- Polycystic ovary syndrome (PCOS)
- Hyperandrogenism
- 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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