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When people talk about diabetes these days, they're generally talking about type 2 diabetes (or T2DM), which used to be called adult onset diabetes, noninsulin dependent diabetes, or insulin independent diabetes. The vast majority of people with diabetes in the United States have type 2 diabetes, and the numbers are growing. About 21 million people have diabetes in the U.S., and about 20 million of them probably have type 2. In the following sections, I explain how type 2 diabetes works and who's at risk for developing it, and I discuss its diagnosis and treatment.

Understanding how type 2 diabetes works

The central problem in T2DM is not lack of insulin (as it is in T1DM; see Chapter 2 for details) but insulin resistance. That is, the body resists the normal, healthy functioning of insulin. Prior to the development of diabetes, when a person's blood glucose is still normal, the level of insulin is abnormally high because the person is resistant to the insulin and therefore more is needed to keep the glucose normal; a shot of insulin doesn't reduce the blood glucose in someone with type 2 diabetes nearly as much as it does in healthy people without insulin resistance. The insulin resistance is caused by a genetic abnormality and is made worse by weight gain and lack of exercise.

When diabetes is present, even though the person actually makes even more than the normal amount of insulin to try to compensate (at least early in the disease), they can't keep the blood glucose in the normal range. It rises to levels greater than 100 mg/dl in the fasting state and 140 mg/dl after eating. This rise results from the body's resistance to its own insulin.

The principal complication that occurs in T1DM but rarely if ever occurs in T2DM is diabetic ketoacidosis (see Chapter 4)

Determining who's at risk for type 2 diabetes

Unlike T1DM, T2DM is strongly inherited. For example, while identical twins with T1DM have a 60 percent chance of both getting T1DM, identical twins with T2DM have a nearly 100 percent chance of both developing T2DM. Nonidentical twins will both develop T2DM 40 percent of the time, but if one has T1DM, there's only an 8 percent chance that the other will develop T1DM.

T2DM also is much more of a lifestyle and environmental disease than T1DM. As lifestyles change and food supplies everywhere have become readily available, the incidence of T2DM has steadily gone up with some exceptions. The countries with the greatest increase in new cases are China and India, places where people previously worked all day in the fields, got around on bicycles, and survived on little food. Today, people in these countries sit in offices, drive cars, and enjoy large meals filled with fat. In other words, they emulate people in the U.S. Another telling example involves Japanese people. In Japan, there's little incidence of T2DM. Japanese who have moved to Hawaii have more cases of T2DM, and those who have moved to the American mainland have the most.

What are the important lifestyle and environmental factors in developing T2DM?

i Central distribution of fat: People with T2DM have apple-shaped rather than pear-shaped bodies. They carry their weight under their belts rather than in their arms and legs. This fat is called visceral fat because it settles around the internal organs in the abdomen, or viscera. Visceral fat is associated with insulin resistance and the development of diabetes as well as coronary artery disease and heart attacks. Fortunately, visceral fat is often the first to go with diet and regular exercise; you only need to lose 5 to 10 percent of your weight to reduce this fat significantly and your chance of getting T2DM or a heart attack as well.

i High body mass index: Doctors determine body mass index (BMI) by looking at weight in relation to height. For example, 150 pounds on a 5 foot 2 inch male is too much weight, whereas 150 pounds on a 5 foot 10 inch male makes him thin.

You can determine your BMI by multiplying your weight in pounds by 703, dividing the result by your height in inches, and dividing that result by your height in inches again. A BMI greater than 25 is considered overweight, and a BMI over 30 is obese in Caucasians.

i Low intake of dietary fiber: A diet low in dietary fiber (as found in whole grains, fruits, and vegetables) is associated with a greater incidence of T2DM. Fiber protects against T2DM in that, among other things, it slows the uptake of glucose from the intestine into the blood.

i Physical inactivity: Every study that compares physically active individuals with physically inactive individuals finds a higher prevalence of T2DM in the sedentary group.

Because the environment plays such a large role in the development of T2DM, it isn't surprising that spouses of people with T2DM have an increased risk of developing it and should be screened by having their blood glucose measured (see the next section for more about screening).

Table 3-1 is intended to help you clearly see the differences between type 1 diabetes and type 2 diabetes.

Table 3-1

Comparison of T1DM and T2DM

Feature

Type 1

Type 2

Internal insulin

Little or none

Normal or increased

Age at diagnosis

Usually children

Mostly adults but increasing in children

Body mass index

Usually normal

Usually overweight or obese

Treatment

Insulin

Diet, exercise, oral agents, insulin

Family history

Uncommon

Common

Relation to HLA

High

None

Presence of antibodies

Usually

Rarely

Condition at diagnosis Very sick Mildly ill

Condition at diagnosis Very sick Mildly ill

Diagnosing type 2 diabetes

Mostly adults are diagnosed with T2DM, although the number of children being diagnosed is increasing. Because T2DM usually presents as a mild illness (whereas folks are usually pretty sick when they're diagnosed with T1DM), the diagnosis depends on finding an abnormal blood glucose either in the fasting state or after food has been eaten. The symptoms of T2DM include fatigue, frequent urination, and thirst, plus vaginal infections in women.

A blood glucose of 126 mg/dl or greater in the fasting state or 200 mg/dl or greater after food consumption is diagnostic of type 2 diabetes. For an accurate diagnosis, these numbers should be found on two occasions separated by a week. The tests are done in the laboratory and are ordered by the primary physician.

The American Diabetes Association recommends that all adults be screened for T2DM beginning at age 45 and every three years thereafter if the initial results are normal. If there's a family history of diabetes or a risk factor such as obesity, the initial screening should take place earlier, as early as age 25. With so much obesity in the U.S. population, I believe that screening should begin in obese children.

Treating type 2 diabetes

Treatment of T2DM begins with lifestyle change. The person with diabetes needs to eat a healthy diet and lose weight, although he or she doesn't have to lose a great deal of weight for the glucose to return to normal. The patient also needs to begin a program of regular exercise, preferably for 30 minutes every day.

If lifestyle change doesn't bring about normalization of blood glucose in the person with T2DM, there are a number of oral agents that can lower the blood glucose. Doctors may consider using the intramuscular drug Byetta either before or after the use of oral agents if the agents aren't successful. Byetta causes weight loss and reverses many of the features of T2DM. If Byetta fails, insulin can be given.

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