Diet & Exercise Delay Type 2 Diabetes

At least 10 million Americans at high risk for Type 2 diabetes can sharply lower their chances of getting the disease with diet and exercise, a major clinical trial indicates.

"In view of the rapidly rising rates of obesity and diabetes in America, this good news couldn't come at a better time," said Health and Human Services Secretary Tommy G. Thompson in announcing the findings Aug. 9 at the National Institutes of Health (NIH). "So many of our health problems can be avoided through diet, exercise and making sure we take care of ourselves."

The study also found that treatment with the oral diabetes drug Glucophage (metformin) reduces diabetes risk, though less dramatically, in people at high risk for Type 2 diabetes.

Participants who were randomly assigned to intensive lifestyle intervention reduced their risk of getting Type 2 diabetes by 58 percent. On average, this group maintained their physical activity at 30 minutes a day, usually with walking or other moderate-intensity exercise, and lost 5 percent to 7 percent of their body weight. Participants picked randomly to receive treatment with Glucophage reduced their risk of getting Type 2 diabetes by 31 percent.

The study, called the Diabetes Prevention Program (DPP), compared diet and exercise to treatment with Glucophage in 3,234 people with impaired glucose tolerance (IGT), a condition that often precedes diabetes. The trial ended a year early because the data had clearly answered the main research questions.

The DPP, conducted at 27 centers nationwide, is sponsored by the NIH. It is the first major trial to show that diet and exercise can effectively delay diabetes in a diverse American population of overweight people with IGT, a condition in which blood glucose levels are higher than normal but the individual is not yet considered to have diabetes.

Forty-five percent of the participants enrolled in the DPP were from minority groups that suffer disproportionately from Type 2 diabetes: African Americans, Hispanic Americans, Asian Americans and Pacific Islanders, and American Indians. The trial also recruited other groups known to be at higher risk for Type 2 diabetes, including people age 60 and older, women with a history of gestational diabetes, and people with a first-degree relative with Type 2 diabetes.

Lifestyle intervention worked as well in men and women and in all the ethnic groups, according to the study's chairman, David Nathan, M.D., of Massachusetts General Hospital in Boston. It also worked well in people age 60 and older, reducing the development of diabetes in this group by 71 percent. Glucophage was effective in men and women and in all the ethnic groups, but was relatively ineffective in the older volunteers and in those who were less overweight.

DPP volunteers were randomly assigned to one of the following groups:

Intensive lifestyle changes with the aim of reducing weight by 7 percent through a low-fat diet and exercising for 150 minutes a week; reatment with Glucophage (850 mg twice a day), a drug approved in 1995 to treat Type 2 diabetes; or standard group taking placebo pills in place of Glucophage. The latter two groups also received information on diet and exercise.

DPP participants ranged from age 25 to 85, with an average age of 51. Upon entry to the study, all had impaired glucose tolerance as measured by an oral glucose tolerance test, and all were overweight, with an average body mass index (BMI) of 34. (A BMI of 25 or more--or 27 after age 35--indicates obesity.) About 29 percent of the DPP standard group developed diabetes during the average follow-up period of three years. In contrast, 14 percent of the diet and exercise group and 22 percent of the Glucophage group developed diabetes.

Volunteers in the diet and exercise group achieved the study goal, on average a 7 percent--or 15-pound--weight loss, in the first year and generally sustained a 5 percent total loss for the study's duration. Participants in this lifestyle intervention group received training in diet, exercise (most chose walking), and behavior modification skills.

Can the interventions prevent diabetes altogether? "We simply don't know how long, beyond the 3-year period studied, diabetes can be delayed," says Nathan. "We hope to follow the DPP population to learn how long the interventions are effective." The researchers will analyze the data to determine whether the interventions reduced cardiovascular disease and atherosclerosis, major causes of death in people with diabetes.