What is Prediabetes?

In today’s New York Times, there is an interesting article in the “Styles” section, front page. The article is entitled ” A Healthy Mix of Rest and Motion,” written by Peter Jaret. In the article, Mr. Jaret discusses the physical fitness benefits of interval training, the technique of alternating fast (very vigorous) and slow (one’s usual energy expenditure for the activity) energy expenditure as a way of improving physical fitness. Those of us who are or were “serious” athletes know only too well about interval training. Until I read this article, I had not really appreciated how effective interval training is in boosting physical fitness. It works well with many activities including walking, running, cycling, rowing, swimming, etc. For me, and I suspect for many, interval training is a “love-hate” relationship; you know it’s good for you but it’s such hard work.

What does interval training have to do with “prediabetes?”

The paragraph above really has nothing to do with prediabetes except that in the article, the author wrote the following: “weight watchers, prediabetics, and those who simply want to increase their fitness all stand to gain,” referring to the technique of interval training. I would be willing to bet that most of the people who read the article do not have any idea what prediabetes is. I’m here to help.

Prediabetes is an old term in the diabetes field but which has been “reinvented” recently. It used to mean a more-or-less theoretical state in which a person was at genetic risk for developing diabetes mellitus or “sugar diabetes” (to distinguish it from diabetes insipidus, a condition related to water balance) but had normal blood sugar levels. More recently, the term is used to define a group of people who are at increased risk for developing diabetes based on specific blood sugar levels, which are above normal but not high enough to allow one to definitively diagnose diabetes. Are you with me so far?


Diabetes is defined by certain blood sugar levels, either in the “fasting state,” which usually means with no caloric intake for the previous 12 hours, or after a standard sugar water drink called a glucose tolerance test. Technically speaking what is measured is the “plasma glucose level” even though many people talk about the “blood sugar level.” Anyway, for a variety of reasons, some scientifically sound and some more politically sound, a person is said to have diabetes if either the fasting plasma glucose is 126 mg/dl or greater on two occasions, or the value two hours after 75 grams of oral glucose is 200 mg.dl or greater. The diagnosis can also be made if a “casual” plasma glucose value (this means testing without regard to interval since the previous meal) is 200 mg/dl or greater with typical symptoms of diabetes- excessive thirst, excessive urination, etc.  There are a number of conditions that need to be met before the diagnosis can be made, such as the person must be well-nourished, not acutely ill, etc. Also, a definitive diagnosis cannot be made using the little portable blood glucose meters that we see advertised on TV; the test must be carried out in a laboratory with actual measurement of the plasma glucose level.

Impaired fasting plasma glucose, impaired glucose tolerance, and prediabetes

This brings us to “prediabetes” states. Diabetes experts define impaired fasting plasma glucose (IFG) as fasting plasma glucose of 100-125 mg/dl; impaired glucose tolerance (IGT) is defined as fasting plasma glucose <126 mg/dl but 2-hour plasma glucose after a glucose tolerance test of 140-199 mg/dl. Finally, prediabetes is defined as either IFG, IGT, or both. Recent studies show that people who have prediabetes are at great risk to develop diabetes within a few years. As it turns out, things are not quite so simple. For example, if the fasting plasma glucose is 100-109 mg/dl, the risk for progression to diabetes from IFG is rather low- much higher if the fasting plasma glucose is in the range 110-125 mg/dl. So?

THe reason it is important to understand these definitions is that recent studies have shown that treating patients with prediabetes can slow progression to diabetes. Thus the very recent American Diabetes Association’s Consensus Statement entitled ” Impaired Fasting Glucose and Impaired Glucose Tolerance” (Diabetes Care 30:753-759) in which it is recommended to treat all people who have either IFG, IGT, or both.  Depending on a number of factors, the treatment would be lifestyle modification and moderate intensity phycical activity (defined as roughly 30 minutes/day) or the above and medications. All of this is to decrease the risk for progression from prediabetes to the real thing, diabetes.


These are bold recommendations that if followed by all medical practitioners would lead to an astonishing increase in testing for IFG and IGT. What I find so amazing is that despite these recommendations, the American Diabetes Association (ADA) and many of the experts who wrote the Consensus Statement discussed above are ambivalent about testing for prediabetes. To quote the recently published ADA’s Clinical Practice Recommendations 2007 (Diabetes Care 30 (suppl 1.):S1-S104, 2007) for diabetes screening: “Screening to detect prediabetes (IGF or IGT) should be considered in individuals >45 yeares of age, particularly in those with a BMI >25 kg/mXm.” They go on to say that screening should be considered in people <45 years of age who are overweight if they have other risk factors for diabetes. How seriously should we take a recommendation of "should be considered."? On the one hand the "experts" tell us we should be treated for prediabetes but our doctors should only "consider" testing us for it. Does any of this make sense to you? What should we do?

Given that about 60% of people in the U.S. are overweight and that we have a diabetes epidemic, we should (not should consider) begin testing on a regular basis (e.g., every 1-2 years) for prediabetes or diabetes in all adults who are overweight. It is the only logical thing to do based on the available scientific information. Why are the “experts” so afraid to speak up? I’m not sure but I suspect there are powerful health-care industry lobbyists who do not feel insurers can cope with the expense of making so many diagnoses of prediabetes and diabetes and then having to treat the patients? Of course, they need not worry; our health-care system is so disorganized that we couldn’t possibly find a way to actually carry out the testing and provide the proper treatment. Am I being unfair? I don’t think so.

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