The answer was of course, "Yes."
The abstract of this article is here:
Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: an analysis from the Whitehall II study.
Dr Adam G Tabák et al. The Lancet The Lancet, Volume 373, Issue 9682, Pages 2215 - 2221, 27 June 2009 doi:10.1016/S0140-6736(09)60619-X
This was a prospective study--i.e. one that takes measurements and then follows the subjects for a set period of time--in this case, almost 10 years, to see what happens. The subjects were 6,538 British civil servants, 71% of them males.
Diabetes was diagnosed using the most conservative measure: subjects had to have a 2 hour glucose tolerance test result over 200 mg/dl. This standard might have missed people who were going over 200 but who were below 200 mg/dl at 2 hours post challenge. Though according to the ADA official diagnostic criteria for Diabetes Mellitus anyone who scores over 200 mg/dl more than once should be considered diabetic. But the use of the 2 hour glucose tolerance test criteria tells us the people in this study who were diagnosed as diabetic were seriously diabetic.
What the researchers found was this: In the subjects who did not become diabetic, "metabolic measures followed linear trends in the group of non-diabetics ... except for insulin secretion that did not change during follow-up.
This finding is important, so let's repeat it: The normal people in this study saw their blood sugar creep up as they got older, but the researchers found that normal people's ability to secrete insulin did not change over time.
In the people who became diabetic,
... a linear increase in fasting glucose was followed by a steep quadratic increase (from 5·79 mmol/L [104 mg/dl] to 7·40 mmol/L [133 mg/dl]) starting 3 years before diagnosis of diabetes."Steep quadratic increase" means that their fasting glucose did not go up gradually, but shot up in a pattern that, when graphed, made a steep upwardly curving parabola.
In addition their 2 hour glucose tolerance test result showed a rapid increase starting 3 years before diagnosis from 7·60 mmol/L [137 mg/dl) to 11·90 mmol/L [214 mg/dl]).
Since we know that lots of people have pre-diabetic blood sugars that don't deteriorate, including the overwhelming majority of insulin resistant obese people who never develop diabetes, it's important to note that it is failing insulin secretion, not insulin resistance, that appears to sort out the people who go on to become diabetic.
Though insulin resistance rose starting five years before diagnosis, in the people who became diabetic,
HOMA β-cell function increased between years 4 and 3 before diagnosis (from 85·0% to 92·6%) and then decreased until diagnosis (to 62·4%).These findings make one thing crystal clear. If you wait for an official diabetes diagnosis--one based on either a fasting glucose test or a two hour glucose tolerance test, you will be giving high blood sugars three years in which to ravage your body.
Consider all the people in this study who were classed as "nondiabetic" because their 2 hour glucose tolerance test result was "only" 180 mg/dl. How high do you think their blood sugars were at 1 hour?
And given that we know that blood sugars that go over 180 mg/dl increase insulin resistance, you have to wonder whether the insulin resistance that was observed to increase five years before diagnosis was due to some independent disease process or whether it was a direct result of the "nondiabetic" blood sugars these people were experiencing after each meal that exposed them to hours of damaging glucose toxicity as their blood sugars remained above 140 mg/dl.
Because, of course, prolonged exposure to blood sugars over 140 mg/dl kills beta cells. Which makes you wonder if the decrease in insulin secretion observed three years before diagnosis, that decrease which happened two years after the high IR was first observed, might have been caused by the subject's blood sugars going over 180 mg/dl meal after meal. Was the decrease in insulin secretion the final result of exposure to "nondiabetic" but much higher than normal blood sugars?
The study I'd like to see would be one that asked: what happens when you find people whose 2 hour glucose tolerance test result is over 140 mg/dl--high enough to damage their organs, and treat them with a protocol that lowers their post-prandial blood sugars by having them cut down on their carbohydrate intake?
Do you see insulin resistance drop when they stop experiencing those 1 hour 180 mg/dl and higher blood sugars after each meal?
Can they preserve their ability to secrete insulin because they aren't exposing their beta cells to those blood sugars over the 140 mg/dl level that we know produces organ damage?
Doctor's aren't likely to do this study, because there are so many medical-political forces fighting against letting the public know that the cheap carbohydrates that enrich the food industry are what raise blood sugars and ruin health. So we aren't likely to get a definitive answer to the question of whether normalizing blood sugars with dietary change can stop the progress to diabetes or not.
But if you have been diagnosed as prediabetic you have nothing to lose by making your own personal experiment to see if keeping your blood sugars in the normal range will prevent your own diabetes from progressing.
You can find out exactly how to do this on this page: How To Get Your Blood Sugar Under Control
Even if it turns out that this technique cannot prevent further progression of diabetes0though it is quite possible it CAN--you have nothing to lose by trying it.
Many of us who have already been diagnosed as diabetic have found that keeping our blood sugars in the normal range prevents us from developing diabetic complications. Since the reason we don't want to have diabetes is because we don't want diabetic complications, prediabetes who adopt a rigorous approach to normalizing their blood sugar with carb restriction will come out way ahead in the future, whatever their glucose tolerance test result might be.
Remember: A diagnosis of Diabetes doesn't cause complications. Prolonged exposure to high blood sugars cause complications. Whatever your diagnosis, if you keep your blood sugars in the normal range 70 mg/dl to 120 mg/dl after meals and under 100 mg/dl fasting you can have normal health.