Insulin resistance can be complicated to study because it's hard to detect. It can go on for so long that your pancreas can't pump out enough insulin to make up for your body's impaired sensitivity to it. The result is type 2 diabetes.
Wouldn't it be easier to study people with insulin resistance who didn't have diabetes? What could these people do to avoid or postpone getting diabetes?
You can delay diabetes.
That's what the Diabetes Prevention Program wanted to know. The U.S. government began this huge program in 1998 and ended it this August, one year ahead of schedule because the results were so clear.
They spent more than $170 million to study 3,234 people with impaired glucose tolerance. People with IGT have blood glucose levels that are higher than normal but not as high as the levels of people with diabetes. A person is considered to have diabetes with a blood glucose reading of 200 mg/dl or more two hours after an oral glucose tolerance test with a glucose-containing solution. If you have IGT, your blood glucose level is between 140 and 199 mg/dl. Normal glucose tolerance is a blood glucose level no higher than 140 mg/dl.
People have IGT because they are insulin resistant. Perhaps 20 million Americans have IGT, even more than those who have diabetes. Since the researchers studied people with glucose levels in the upper half of the IGT range, the findings strictly apply to the 10 million people with similar glucose levels. But it's reasonable to assume that anyone with insulin resistance would benefit from the treatments these people got.
What treatments? Originally, the program randomly divided the volunteers into four groups. The first promoted intensive lifestyle changes with the aim of reducing weight by 7 percent through a low-fat diet and exercising for 150 minutes a week.
The three other groups got information but no direct encouragement on diet and exercise. The second group also got 850 mg of Glucophage twice a day, because one of the things that Glucophage does is to increase insulin sensitivity. The third group took a placebo in place of Glucophage. The fourth group, which used Rezulin, was discontinued near the beginning of the program in June 1998, almost two years before the Food and Drug Administration took it off the market because of the possibility of liver damage.
About 10 percent of those people in the placebo or control group developed diabetes each year of the study. The lifestyle change or diet and exercise group did much better. They cut their chances of getting diabetes by 58 percent. Those in the study on Glucophage cut their chances of getting diabetes by 31 percent.
As much as the study showed it left many questions unanswered. They know that diabetes can be delayed, but not whether they can prevent it altogether. They know that intensive diet and exercise changes together get great results, but don't know which one is more important.
The biggest unknown is how much two drugs recently approved to treat diabetes will help prevent it. Avandia and Actos, which specifically target insulin resistance among people with diabetes, came on the market while the program was underway.
The FDA hasn't approved Glucophage, Avandia, and Actos for IGT. To use them for an unapproved purpose, as Glucophage was in the trial, is considered "off-label." Still, it is legal for doctors to prescribe drugs off-label, and the FDA will determine whether to make diabetes prevention an approved use.
This article originally appeared on HealthTalk Interactive, but is no longer online there.
|After this article appeared on the HealthTalk Interactve website in November 2001, the official name of impaired glucose tolerance (IGT) became pre-diabetes. See http://diabetes.niddk.nih.gov/dm/pubs/diagnosis/index.htm|
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