Millions of overweight Americans at high risk for type 2 diabetes can delay and possibly prevent the disease with moderate diet and exercise, a major clinical trial has found.
The same study found that the oral diabetes drug metformin (Glucophage) also reduces type 2 diabetes risk, although not as effectively as lifestyle changes. Researchers announced results of the trial, called the Diabetes Prevention Program (DPP), last August after ending the study a year early. The study results are reported in the February 7 issue of the New England Journal of Medicine.
"This research conveys a powerful message of hope to individuals at risk for type 2 diabetes, a painful, life-threatening disease that has been increasing in this country along with obesity," said HHS Secretary Tommy G. Thompson.
"By adopting a moderate, consistent diet and exercise programme, many people with one or more of the risk factors for type 2 diabetes can stop the disease before it becomes irreversible."
The DPP compared three approaches - lifestyle modification, treatment with metformin, and standard medical advice - in 3,234 overweight people with impaired glucose tolerance (IGT), a condition in which blood glucose levels are higher than normal but not yet diabetic.
About 20 million people in the United States have IGT, which raises the risk of developing type 2 diabetes and cardiovascular disease. Once a person has type 2 diabetes, the risk of heart and blood vessel disease is even greater - two to four times that of people without diabetes.
Diet and exercise that achieved a five to seven per cent weight loss and reduced diabetes incidence by 58 per cent in participants chosen at random for the study's lifestyle intervention group. Participants in this group exercised at moderate intensity, usually by walking an average of 30 minutes a day five days a week, and lowered their intake of fat and calories. Volunteers randomly assigned to treatment with metformin had a 31 per cent lower incidence of type 2 diabetes. Metformin lowers blood glucose mainly by decreasing the liver's production of glucose.
"Lifestyle intervention worked equally well in men and women and in all the ethnic groups. It was most effective in people aged 60 and older, who lowered the risk of developing diabetes by 71 per cent. Metformin was also effective in both sexes and in all the ethnic groups, but it was relatively ineffective in older volunteers and in those who were less overweight," said study chair Dr David Nathan of Massachusetts General Hospital, Boston.
Both interventions lowered fasting blood glucose levels, but lifestyle changes more effectively lowered blood glucose levels two hours after a glucose drink. Also, about twice as many people in the lifestyle group compared to placebo regained normal glucose tolerance, showing that diet and exercise can reverse IGT.
"Not only did changes in diet and physical activity prevent or delay the development of diabetes, they actually restored normal glucose levels in many people who had impaired glucose tolerance," said Dr Allen Spiegel, director of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the part of the National Institutes of Health (NIH) that sponsored the study.
"These findings bring us closer to the goal of containing and ultimately reversing the epidemic of type 2 diabetes in this country."
About 16 million people in the United States have diabetes. It is the main cause of kidney failure, limb amputations, the onset of blindness in adults and a major cause of heart disease and stroke. Type 2 diabetes accounts for up to 95 per cent of all diabetes cases. According to the researchers type 2 diabetes is strongly associated with obesity (more than 80 per cent of people with type 2 diabetes are overweight), inactivity, family history of diabetes, and racial or ethnic background. In the last thirty years the prevalence of type 2 diabetes has tripled in the US.