Wednesday, November 28, 2007

Understanding Diabetes

Types of Diabetes

There are different types of diabetes, and the causes for the elevations in blood sugar differ depending on the type of diabetes you have. In this book I focus on the two major types of diabetes. The first form of diabetes that I'll discuss is called type 1 diabetes mellitus (or simply type 1 DM), sometimes referred to as insulin-dependent diabetes (IDDM), because people with this type of diabetes are reliant on an external source of insulin, which is injected. Type 1 DM is a condition in which the blood sugar levels are elevated because there is no production of insulin by the pancreas. In other words, these people do not produce the keys to the doors of the cell, and thus the glucose in the bloodstream cannot get into the cell. These people have symptoms early in their lives, typically occurring in childhood or when they are young adults. Some people with type 1 diabetes may have inherited susceptibility this condition. We think that in these people there is a reaction in the body that destroys insulin-producing cells in the pancreas, making it necessary for these people to take insulin in order to survive.

Two types of diabetes: (a) With type 1 diabetes, insulin is not present, so the glucose cannot get into the cell. (b) With type 2 diabetes, insulin is present, but the cell is less sensitive to it, so the glucose has a hard time getting into the cell.

The second type of diabetes is called type 2 diabetes mellitus (type 2 DM), sometimes referred to as non-insulin-dependent diabetes (NIDDM), because people with this type of diabetes typically do not need to take insulin (although some with type 2 diabetes will require insulin to control their glucose). This form of diabetes accounts for around 95 percent of people who have diabetes, and this form is the primary focus of this book. As in all cases of diabetes, those with type 2 have elevated blood glucose levels. However, unlike those with type 1, these people can produce insulin. Some even may produce more insulin than normal. The problem in this case has not much to do with the "key,"-insulin, but rather with the door's keyhole that allows it to open. If you have type 2 diabetes you have a high glucose level and either a low, normal, or high insulin level at the same time. The main problem in this case is that your cells are significantly less sensitive - or more resistant to - insulin and, in an attempt to keep the level of glucose inside the cells normal, the body creates a high concentration of glucose outside of the cells (see figure 1.2b). A type of diabetes similar to type 2 diabetes occurs during pregnancy, and I briefly discuss this later in this chapter. However, the information in this book is not intended as a comprehensive resource for those who are pregnant but only to give you a basic understanding of this condition.

Diagnosing Diabetes

Those with type 2 diabetes are usually diagnosed in their 30s. However, we are seeing more and more patients diagnosed in their teenage years. There may be a genetic predisposition, similar to that of type 1 diabetes, that may be linked to the development of type 2 diabetes. However, unlike those with type 1 diabetes, many people with type 2 diabetes (60 percent) are obese. This is likely due to a combination of genetic factors and may be a result of the body's need to take in more calories to keep blood sugar levels high enough for cells to function.

The common symptoms of type 1 and type 2 diabetes are similar and are directly related to the body's response to high blood sugar levels. The classic symptoms include excessive urination and thirst. When glucose is present in high levels in the blood, the kidneys produce higher volumes of urine. Thus, a person with untreated diabetes will have to empty the full bladder often. This can cause the body to become dehydrated, triggering the thirst response, resulting in excessive drinking. The volume of fluid that is lost in the urine is often great. And if this fluid is not replaced, the person can experience symptoms of dehydration as well, such as dizziness, headache, and rapid heart rate. Other symptoms include blurred vision, infections, and weight loss despite an increase in appetite and food consumption.

A major difference between type 1 and type 2 diabetes is that those with type 1 diabetes are absolutely dependent on an external source of insulin to live. These people may be presented with life-threatening symptoms. For example, if the person with type 1 diabetes does not have insulin, he will start to metabolize other energy sources in the body (such as fat) that produce harmful substances that can lead to death. This condition is called diabetic ketoacidosis (DKA). It is rare for someone with type 2 diabetes to develop DKA unless he is under very stressful conditions, such as a major illness.

The difference in body weight between those with type 1 and type 2 diabetes is commonly related to the effects insulin has on the body. Insulin supports growth of body tissues, including fat. People with type 1 diabetes, as discussed earlier, do not produce their own insulin, so they need to balance what they eat with the amount of insulin they take in order to keep their blood glucose levels normal. People with type 2 diabetes typically produce enough insulin and sometimes even two or three times the normal amount of insulin. In a person with untreated type 2 diabetes, the body senses that there is a low level of glucose inside the cells (despite having high levels in the blood), and the insulin level is increased and the hunger center in the brain is activated, driving the person to eat more. This combination of events often causes the person with type 2 diabetes to overeat, which leads to obesity.

Does everyone with diabetes have symptoms? Often there are symptoms. But just as often the diagnosis is made without the presence of symptoms, during routine health examinations that include blood sugar screenings. Elevated blood sugar prompts the health care provider to seek a cause of this irregularity. The physician may run more tests if an initial blood test is abnormal; she may review family history as well. We typically screen patients for diabetes starting at age 45. However, if a patient is in a high-risk group (African American, Asian, Latino, Native American) or has risk factors for diabetes (such as obesity, high blood pressure, high blood lipid levels, or a first-degree relative with diabetes), we screen the patient for diabetes earlier than age 45.

Physicians prefer to have blood glucose tested in the morning, before the patient has eaten. This is called a fasting glucose test. We consider a normal fasting glucose test to be less than 110 mg/dl (milligrams per deciliter). If a person's fasting glucose level is between 110 and 126 mg/dl, then we consider this person to have prediabetes, or what is often referred to as glucose intolerance. Fasting glucose levels above 126 mg/dl on two separate occasions are indicative of diabetes mellitus. If you have a test after you have already eaten (or what is described as a nonfasting glucose test), and it shows your blood glucose level to be above 200 mg/dl, then this is enough to make the diagnosis of diabetes mellitus (see Table 1.1).

There are other tests that may be done as well, such as a glucose tolerance test. The glucose tolerance test involves doing a fasting glucose test and then having the patient drink 75 milligrams of glucose and remeasuring the blood glucose levels after two hours. The test is normal if the fasting glucose is less than 110 mg/dl and the two-hour glucose level is less than 140 mg/dl. If the two-hour results show a level between 140 and 200 mg/dl, then this is indicative of glucose intolerance; up to 5 percent of patients with this level of blood glucose will develop diabetes. A two-hour glucose level greater than 200 mg/dl is indicative of diabetes.

Your doctor may also choose to do another test commonly referred to as the hemoglobin A(HbA). This is a test designed to give your health care provider a rough estimate of how high your blood glucose levels have been over the last three months. This can help your physician in deciding how often to check your glucose as well as in formulating your treatment plan. For instance, if your initial test confirms the diagnosis of type 2 diabetes with two fasting glucose levels of 130 mg/dl, that is just above the diagnostic threshold of 126 mg/dl. But if your HbA1C is significantly elevated, your doctor may decide to monitor you more closely and treat your condition more aggressively. This may include starting a medication regimen earlier in addition to making changes in your diet and exercise habits. It is important to note that if you are diagnosed with type 1 diabetes, then you will start taking medication (insulin) immediately.

Table 1.1 Glucose Levels and What They Mean


Glucose level

Normal fasting glucose



110-126 mg/dl

Diabetes (2 separate measurements)

>126 mg/dl

Diabetes (nonfasting)

>200 mg/dl

Other tests can differentiate between type 1 and type 2 diabetes if it becomes difficult to do through questioning the patient about symptoms. A certain molecule called C-peptide is part of the precursor molecule to the insulin molecule. When insulin is formed in the pancreas, the C-peptide separates from the insulin portion of the molecule and can be measured in the blood of those with type 2 diabetes, whereas it is not present in those with type 1 diabetes, because they do not produce insulin.

Treatment Basics

At this point you should have a working knowledge of diabetes. It should be clear that those with diabetes are characterized as having abnormally high blood glucose levels and that there are different forms of diabetes. The main difference between type 1 and type 2 diabetes is in the treatment: People with type 1 diabetes require treatment with an external source of insulin, and those with type 2 diabetes are typically treated initially with a modification of their diet and exercise habits because exercise can make the body more sensitive to insulin (Devlin 1992). However, some people with type 2 may require medication to help them produce more insulin or to make them more sensitive to it (see table 1.2). Some with type 2 may even require injections of insulin to control their glucose levels. Using exercise as a treatment for type 2 diabetes is the focus of this book. I discuss important issues concerning the use of exercise in the treatment of type 1 diabetes as well.

The main goal of treating diabetes is to prevent complications of the disease. Many studies have shown that keeping the blood glucose at normal levels can be effective in eliminating the symptoms and slowing or preventing the potentially devastating complications associated with diabetes. We will discuss these complications in more detail in the following chapters.

How many times have you heard someone say, just eat right and exercise - If it were as easy as it sounds, type 2 diabetes would not be nearly as common as it is. But eating right and exercising are not easy. Most of us do not even understand what "eating right" is. Our society inundates us with advertisements that encourage us to eat more. When was the last time that you were at a fast-food drive-up window and the attendant asked you if you'd like to decrease the size of your value meal?

Table 1.2 Treatment of Type 1 and Type 2 Diabetes


Type 1 diabetes

Type 1 diabetes


Yes (all)

Yes (rare)

Hypoglycemic agents


Yes (common)


Yes (reduces complications but does not treat diabetes)


Healthy diet

Yes (reduces complications but does not treat diabetes)


The most common excuse that I hear is, "I do not have time to exercise."-Typically, this response comes from a person who does not understand how useful exercise can be in treating the condition. It is well known that exercise can improve almost anyone's health. People who have type 1 diabetes can benefit from exercise as well. But for someone with type 2 diabetes, exercise is a major component of treatment and in many cases may prevent the disease. The addition of physical activity to your life may be the only treatment you need for your diabetes.

You now have a good foundation of knowledge about your disease, which will help you understand the steps to creating your action plan for healthful living.

Making Glucose Control Your Goal

Many scientific studies show that the most effective way to decrease or eliminate the complications associated with diabetes is to keep blood glucose at or near normal levels. Most health problems that are associated with diabetes arise without many symptoms. Not knowing this simple fact can be a major roadblock to living a healthy life. If you don't know that a threat to your life exists, then how can you attempt to prevent it? Say you have 45,000 miles on your car and you want to drive your car 20 miles down a steep canyon. Tucked away in the glove box is the manual that states that the braking system should be serviced at 40,000 miles to prevent its potential failure. And say that you did not happen to read every page of your car's manual and did not know this particular fact. You would likely drive down the canyon completely unaware of the potential danger that lies ahead. Likewise, if glucose control is not your goal, potential dangers lie ahead. In this chapter we discuss the complications of poorly controlled diabetes.

The visual system (eyes), renal system (kidneys), cardiovascular system (heart), peripheral vascular system (blood vessels in the extremities), nervous system (nerves), gastrointestinal system (stomach and intestines), and immune system (infection control) are the bodily systems affected by poor diabetes control. Given that many of these systems interrelate, I discuss diabetes as it relates to vision, the kidneys, the heart and blood vessels, and the nervous system. The effects on gastrointestinal and immune system are discussed as well. These complications are summarized in table 2.1.

Table 2.1 Systems Affected by Diabetes

Organ system

Common signs and symptoms

Ocular system (eyes)

Blurred vision, blindness

Renal system (kidneys, bladder)

Protein wasting in urine, high blood pressure, urinary tract infections

Cardiovascular system (heart)

Coronary artery disease, heart attack

Peripheral vascular system (blood vessels of the arms and legs)

Leg and foot pain with activity, skin and soft-tissue breakdown

Central nervous system (brain)

Stroke or cerebral vascular incident

Peripheral nervous system (nerves in the torso, arms, and legs)

Foot numbness and pain, foot ulcers, nausea, vomiting, diarrhea, loss of bladder control, light-headedness, loss of consciousness

Immune system (infection-control system)

Frequent infections (skin and bladder infections are common)

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