One of the largest diabetes studies, the Diabetes Prevention Program (DPP), showed that, in people at high risk for the disease, modest weight loss of 5 percent to 10 percent of body weight, coupled with increased physical activity, lowered by 58 percent the risk of developing type 2 diabetes.
These encouraging findings have motivated doctors to emphasize the importance of lifestyle measures to their patients.
Another significant DPP finding was that metformin, a drug used to treat type 2 diabetes, reduced by 31 percent the progression to diabetes in people at risk. The benefit of metformin was substantially greater in those who were younger and obese. Until recently, however, metformin was not commonly recommended for the prevention of diabetes.
Although lifestyle measures are still recommended, a new consensus statement from the American Diabetes Association (ADA) has now suggested consideration of metformin, 850 mg twice daily, as a treatment option for people with prediabetes. Prediabetes, defined as having a fasting blood glucose between 100 and 125 mg/dL, is associated with as much as a 70 percent likelihood of developing type 2 diabetes.
The FDA had already approved metformin to treat, but not to prevent, diabetes. Once a drug has received FDA approval, however, physicians can then legally prescribe it for other therapeutic or preventive uses — and a recent study indicated that in fact about 20 percent of all prescriptions are "off-label." This ADA statement on metformin marks the first time that that organization has recommended an "off-label" use of a drug.
To be eligible for metformin therapy to prevent diabetes, an individual must have two abnormal blood tests on separate days — impaired fasting glucose and impaired glucose tolerance (blood glucose between 140 and 199 mg/dL 2 hours after a standard oral dose of glucose) — and must meet at least one of the following criteria:
- Younger than age 60
- Body mass index (BMI) of at least 35
- History of diabetes in a sibling, parent, or grandparent
- Elevated triglycerides
- Reduced HDL cholesterol
- A1c greater than 6 percent
People with prediabetes who have unsuccessfully tried lifestyle measures such as diet and exercise should ask their doctors whether metformin is an option for them.
Those who already have type 2 diabetes also need to advise their close family members to have a fasting glucose test for prediabetes and diabetes. Testing is also a good idea for overweight people and for members of groups at high risk for type 2 diabetes: African Americans, Hispanic Americans, Asian Americans, American Indians, and Pacific Islanders, especially if they are obese or have a positive family history for type 2 diabetes.
A more recent study has shown that rosiglitazone (Avandia), another medication to treat diabetes, reduced the development of type 2 diabetes in high-risk patients by about 60 percent. Although rosiglitazone is not yet recommended for the prevention of diabetes, such a use may be suggested in the future.
