Diet, Exercise Delays 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, according to the findings of the Diabetes Prevention Program (DPP), a major clinical trial conducted by Massachusetts General Hospital (MGH) and 26 other medical centers nationwide.
“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. “So many of our health problems can be avoided through diet, exercise and making sure we take care of ourselves. By promoting healthy lifestyles, we can improve the quality of life for all Americans, and reduce health care costs dramatically.”
The same study found that treatment with the oral diabetes drug metformin (Glucophage®) also reduces diabetes risk, though less dramatically, in people at high risk for type 2 diabetes.
Participants 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 per day, usually with walking or other moderate intensity exercise, and lost 5-7 percent of their body weight. Participants randomized to treatment with metformin reduced their risk of getting type 2 diabetes by 31 percent.
“Every year a person can live free of diabetes means an added year of life free of the suffering, disability, and the medical costs incurred by this disease,” said David Nathan, MD, director of the MGH Diabetes Unit and national chair of the DPP study.”The Diabetes Prevention Program findings represent a major step toward the goal of containing and ultimately reversing the epidemic of type 2 diabetes in this country. We are very grateful to the more than 3,000 individuals who participated in this national study.”
Diabetes Prevention Program
The findings came from the Diabetes Prevention Program, a major clinical trial comparing diet and exercise to treatment with metformin in 3,234 people with impaired glucose tolerance, a condition that often precedes diabetes. On the advice of the DPP’s external data monitoring board, the trial ended a year early because the data had clearly answered the main research questions.
Smaller studies in China and Finland have shown that diet and exercise can delay type 2 diabetes in at-risk people, but the DPP, conducted at 27 centers nationwide, is the first major trial to show that diet and exercise can effectively delay diabetes in a diverse American population of overweight people with impaired glucose tolerance (IGT). IGT is a condition in which blood glucose levels are higher than normal but not yet diabetic.
Of the 3,234 participants enrolled in the DPP, 45 percent are 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 individuals 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. It also worked well in people age 60 and older, who have a nearly 20 percent prevalence of diabetes, reducing the development of diabetes by 71 percent. Metformin was also 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,” said DPP study chair Nathan.
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.
- Treatment with the drug metformin (850 mg twice a day), approved in 1995 to treat type 2 diabetes.
- A standard group taking placebo pills in place of metformin.
The latter two groups also received information on diet and exercise.
A fourth arm of the study, treatment with the drug troglitazone combined with standard diet and exercise recommendations, was discontinued in June 1998 due to the potential for liver toxicity.
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.
About 29 percent of the DPP standard group developed diabetes during the average follow-up period of 3 years.
In contrast, 14 percent of the diet and exercise arm and 22 percent of the metformin arm developed diabetes.
Volunteers in the diet and exercise arm 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 the lifestyle intervention arm received training in diet, exercise (most chose walking), and behavior modification skills.
Can Diet and Exercise Prevent Diabetes
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 type 2 diabetes.
Rates of Diabetes
Diabetes afflicts more than 16 million people in the United States. It is the main cause of kidney failure, limb amputations, and new onset blindness in adults and a major cause of heart disease and stroke. Type 2 diabetes accounts for up to 95 percent of all diabetes cases. Most common in adults over age 40, type 2 diabetes affects 8 percent of the U.S. population age 20 and older. It is strongly associated with obesity (more than 80 percent of people with type 2 diabetes are overweight), inactivity, family history of diabetes, and racial or ethnic background. Compared to whites, black adults have a 60 percent higher rate of type 2 diabetes, and Hispanic adults have a 90 percent higher rate. The prevalence of type 2 diabetes has tripled in the last 30 years, and much of the increase is due to the dramatic upsurge in obesity. People with a BMI of 30 or greater have a fivefold greater risk of diabetes than people with a normal BMI of 25 or less.
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