Defining Diabetes

It is often said that you either have type 2 diabetes or you don't. Your physician may tell you that you can't have just a touch of diabetes or be a little bit diabetic. Why is this? The main reason is that there is a definition of diabetes based on several strict criteria and you either meet the criteria or you don't. The criteria are as follows:

1. Fasting blood sugar > 6.9 millimoles/litre (mmol/l)
   Individuals are asked to refrain from eating for 12 hours prior to going to the lab to have a blood sample drawn and the sugar concentration of blood plasma determined. A normal fasting blood sugar is < 6.0 mmol/l.
   
   or
   
   
2. Fasting blood sugar between 6.1 and 6.9 mmol/l and a 2 hour post-glucose load blood sugar >11.0.
   The Oral Glucose Tolerance Test (OGTT) is used to determine the latter criteria by having individuals consume a drink containing 75 grams of pure glucose and then measure the blood plasma glucose concentration 2 hours later.

Health care professionals use these diagnostic criteria in order to make decisions regarding patient care. If diagnosed as diabetic you will be referred to a doctor who specializes in diabetes care and possibly sent for education and counseling at a diabetes clinic.

What if you almost meet the criteria?

Individuals who have a fasting blood sugar between 6.1 and 6.9 mmol/l but who have OGTT values between 7.8 and 11.0 mmol/l are referred to as having Impaired Glucose Tolerance. They are not defined as diabetic but it is estimated they have a 5% annual probability and a 35% lifetime probability of becoming diabetic. They are walking around with blood sugars higher than normal much of the time and this can affect their health. Many of these individuals are on the road to becoming diabetic.

A second group that almost meets the criteria are those who have a fasting blood sugar between 6.1 and 6.9 mmol/l but their OGTT result comes back < 7.8 mmol/l (normal). These individuals are referred to as having Impaired Fasting Glucose (or Impaired Glucose Homeostasis). Although the probability of these individuals becoming diabetic may not be as high as the Impaired Glucose Tolerant group it is usually a warning sign.

From a diagnostic perspective you either have diabetes or you don't based on these criteria.

From a physiological perspective there is a gradient from the normal individuals where glucose is well controlled to the type 2 diabetic where glucose levels are out of control. The nature of the disease is such that you don't go from one end of the gradient to the other overnight. It is a gradual process as the body becomes more resistant to insulin and the pancreas is unable to provide adequate amounts of insulin to overcome the resistance. The liver can also play a role producing excessive amounts of glucose resulting in elevated blood glucose levels.

Symptoms of Hypoglycemia (Low Blood Sugar) and Hyperglycemia (High Blood Sugar)
Lows: Sweats Shakes Hunger Dizziness Fatigue Irritable Fast Heartbeat	Highs: Extreme Thirst Frequent Urination Dry Skin Drowsiness Blurred Vision

How prevalent is undiagnosed diabetes and glucose intolerance?

In 1998 a group of researchers asked this very question with regards to the Canadian population¹. They designed a program to have family physicians screen their patients (over 40 years of age) for diabetes. The physicians were randomly selected to ensure accurate representation of the Canadian population, balancing proportions between provinces as well as between rural and urban settings and between men and women. They enrolled 9,042 patients in this study.

What did they find?

They found that 2.2% of the group they screened had diabetes and didn't know it. Another 3.5% of the group screened had either Impaired Glucose Tolerance (0.6%), Impaired Fasting Glucose (2.5%) or were probably diabetic (0.4%, based on incomplete information). These numbers are close to a previous estimate² that 3-5% of Canadians are walking around with undiagnosed type 2 diabetes. Hyperglycemia (high blood sugars) associated with type 2 diabetes develops gradually and type 2 diabetes is often only recognized 5-12 years after hyperglycemia develops³. Prior to a type 2 diabetes diagnosis, prolonged hyperglycemia may have already caused some damage to target tissues⁴ (heart, eyes, kidneys, nerves). This can occur in the absence of the classic symptoms of diabetes (see the list below). This is why early detection is critical and why screening programs for diabetes are rapidly expanding.

Equally important is the early detection of impaired glucose tolerance and impaired fasting glucose. Detecting these warning signals can permit early intervention and halt the damage caused by persistent hyperglycemia. Typically these physiological states are warning signs that your diet and exercise habits aren't suited to your genetic make-up. They may be suited to your friend Fred down the street who eats and does exactly what you do and yet stays slim and trim; but you aren't Fred. Genetics plays a huge role in determining our susceptibility to type 2 diabetes and the stages preceding it. The accumulating evidence suggests that there are as many as ten or more genes that may play a role in the onset of type 2 diabetes. If you are diagnosed with type 2 diabetes or any of the stages preceding it you will have to learn to modify your lifestyle in order keep your genes happy.

Is type 2 diabetes preventable?

In most cases type 2 diabetes is a preventable disease. It has been said that type 2 diabetes is the result of a "clash between genes and the environment".⁵ Since we can't change our genes, not at this point in time anyway, we need to change the environment, more specifically our diet and exercise habits. But does it really work? A Finnish research group decided to try to answer that question.⁶

The Research Study. They recruited 522 middle-aged, overweight subjects with impaired glucose tolerance. This population was chosen because they have a greater probability of developing diabetes making it possible to show significant effects of the study intervention in a relatively small study population in just a few years.

Volunteers with impaired glucose tolerance were randomized to either a control group or an intervention group. The control group was given general oral and written information about diet and exercise at the start of the study and at each annual visit thereafter. There were no individualized programs offered to the control group.

The Intervention. The intervention group was more intensive. They were given detailed advice about how to achieve the goals of the intervention; the goals being 1. a reduction in weight of 5% or more 2. total intake of fat less than 30% of energy consumed 3. saturated fat less than 10% of energy consumed 4. increased fibre and 5. thirty minutes of exercise a day. Nutritional advice was tailored to each subject based on food records. Volunteers in this group had 7 sessions with a nutritionist during the first year and every three months thereafter. These volunteers also received information on increasing their level of physical activity including both endurance training and strength training.