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:
- 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.
- 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)|
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.
Did it make a difference?
At baseline the characteristics of both groups were identical in all respects. They observed that during the trial (mean follow-up of 3.2 years) the cumulative incidence of diabetes was 58% lower in the intervention group (63% for men and 54% for women) compared to the control. But this is conservative since not all those in the intervention group adhered to their recommendations, and for ethical reasons, the control group also received some guidance.
In the assessment they went one step further and looked at how successful the individuals were in achieving the goals of the intervention. This adherence was assessed for all 5 recommendations listed earlier. In those individuals who achieved 4 or 5 of the goals there was no one who developed diabetes after a mean of 3.2 years follow-up. Alternatively, when none of the goals were achieved, diabetes appeared in 38% and 31% of the intervention and control group, respectively. The message here being you can join as many gyms as you want and see a dietician regularly but unless you are willing to actually make the changes it is not going to help you. It is important to remember that a weight loss of as little as 5% can make a huge difference in the incidence of diabetes. In other words, the changes don’t have to be overwhelming. Setting reasonable goals and taking small steps in the right direction can pay off.
A publication last year by the Diabetes Prevention Program Research Group7 recruited a similar population of glucose intolerant individuals (3234 non-diabetic persons) and implemented a lifestyle intervention similar to that of the Finnish study. They had goals of 7% weight loss and 150 minutes/week of physical activity along with a reduction in fat intake and total caloric intake. In this large group they found a similar 58% reduction of the incidence of diabetes compared to their control group. This effect occurred in all subgroups of men and women of all ages from all racial and ethnic groups. The interventions work!
The above mentioned study also had a medication arm that involved taking 850 mg of metformin twice daily. Metformin is a diabetes medication that reduces the production of glucose by the liver and is effective in that it effectively reduces fasting blood glucose. In the research study metformin was found to reduce the progression to diabtes by 31 percent relative to the controls. While not as effective as a lifestyle intervention, it was significant. There are now several large research studies underway recruiting a similar glucose intolerant population and treating them with other diabetes medications. Some of these medications stimulate insulin release from the pancreas while others increase insulin sensitivity. The results of these studies are not yet available but should prove interesting. In the meantime we already know what works and it doesn’t require a prescription. Lifestyle changes!
Screening is important? Before getting screened you should consider risk factors for type 2 diabetes. Some risk factors to consider are:
- Greater than 40 years of age
- Central obesity
- Has a parent sibling or child with diabetes
- High risk ethnicity (Hispanic, aboriginal Canadian, Asian, African-Canadian, Pacific Islander)
- Had gestational diabetes
- Has given birth to a baby weighing more than 10 pounds.
If the results of your test indicate you are glucose intolerant based on any of the criteria you should take action early on.
Why wait? You can get started right now of course without even going to your physician or a clinic and it won’t cost you or the health care system a penny. Put on your shoes and go for a walk. Consider what you now know to be some steps of a diabetes prevention program as outlined in the research study I discussed. Think of how you can incorporate some or all of these recommendations into your life.
Why should I bother if I’m not at risk for acquiring diabetes? The interventions used in this study to prevent diabetes are excellent recommendations for everyone. They are fundamentals of what we know to be a health promoting lifestyle. They can make you feel better, sleep better, have more energy and prevent or delay other health problems such as heart disease and osteoporosis. This is true whether or not you have any form of glucose intolerance.
In summary the recommended changes in lifestyle should include changes in diet and exercise. More specifically I would recommend the following goals.
Dietary goals: Aim for a total fat intake of less than 30% of total energy consumed and reduce saturated fat to 10% or less. You may also want to reduce your cholesterol intake as well. Boosting your fibre intake to greater than 15 grams/1000 calories is a good idea. If you smoke then stop as soon as possible. Learn as much as you can about nutrition and incorporate that information into the fabric of your life.
Exercise goals: Strive to improve cardiovascular fitness. Brisk walks, cycling, swimming, running. It doesn’t have to be one big workout. Research has shown that you still benefit from a small number of shorter activities during a day. For example, two or three 15-20 minute walks during the day if you don’t feel you have time for one big 45 minute walk. Whatever works for you. Be sure to consult your physician if you have any doubts about whether you should engage in a fitness activity.
Strength training should also be considered given our current understanding of glucose disposal and muscle mass. It is also excellent for your bones. Be sure to consult an instructor if you are using weights for the first time and start slowly, gradually increasing your intensity as your strength increases and your body becomes accustomed to the activity. The combination of cardiovascular fitness activities and weight training should equal about 4 hours per week.
Eric Norman is a research scientist investigating heart disease in post-menopausal women and in individuals with type 2 diabetes.
- Diabetes Screening in Canada (DIASCAN) Study. Leiter et al., June 2001. Volume 24 Number 6. Diabetes Care.
- Tan H and DR Maclean. 1995.Epidemiology of diabetes mellitus in Canada. Clin Invest Med.. Volume 18:240-246.
- Muggeo, M. 1998. Accelerated complications in type 2 diabetes mellitus: the need for greater awareness and earlier detection. Diabet Med 15 (Suppl. 4): S60-S62.
- The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus:Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. 2000. Diabetes Care Volume 23 (suppl 1):S4-S19.
- Bloomgarden, Z.T. 2000.European Association for the Study of Diabetes Annual Meeting. Diabetes Care Vol 24, No 6. June. 1115-1119.
- Tuomilehto et al., May 3, 2001. Prevention Of Type 2 Diabetes Mellitus By Changes In Lifestyle Among Subjects With Impaired Glucose Tolerance. Volume 344 Number 18. New England Journal of Medicine.
- Diabetes Prevention Program Research Group. Feb 7, 2002. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. Volume 346 Number 6. New England Journal of Medicine.