Diet and exercise cut type 2 diabetes risk drastically, study finds

A lifestyle intervention of diet and exercise helped people at high risk for type 2 diabetes lower their chances of developing the disease by 58 percent. Rena Wing, professor of psychiatry and human behavior at Brown University, designed the intervention.

PROVIDENCE, R.I. — A new study of 3,234 people at 27 medical centers nationwide shows that diet and exercise helped people at high risk for type 2 diabetes lower their chances of developing the disease by 58 percent.

At least 10 million Americans are at high risk for type 2 diabetes. “Losing just 15 pounds and walking or doing other physical activity for about 30 minutes a day would markedly reduce their risk of developing diabetes,” said Rena Wing, who designed the study’s diet and exercise intervention.

Wing is a professor of psychiatry and human behavior at Brown University and director of the Weight Control and Diabetes Research Center at Miriam Hospital. She also oversaw one of the study’s research sites, located at the University of Pittsburgh, where she maintains an appointment as a professor of psychiatry, psychology and epidemiology.

Type 2 diabetes has reached epidemic status in the United States due primarily to the increasing incidence of obesity and the aging of the nation’s population. Diabetes afflicts more than 16 million Americans. Type 2 diabetes accounts for up to 95 percent of all cases. Diabetes is the main cause of kidney failure, limb amputations and new onset blindness in adults, and is a major cause of heart disease and stroke.

“In view of the rapidly rising rates of obesity and diabetes in America, this good news couldn’t come at a better time,” said Tommy G. Thompson, secretary of Health and Human Services. “So many of our health problems can be avoided through diet, exercise and making sure we take care of ourselves.” Primary funding for the study came from the National Institutes of Health.

The findings come from the Diabetes Prevention Program (DPP), a clinical trial that compared diet and exercise to treatment with the oral diabetes drug metformin in people with impaired glucose tolerance, a condition that often precedes diabetes.

On average, participants randomly assigned to the intensive lifestyle intervention of diet and exercise maintained physical activity at 30 minutes per day, usually via walking or other moderate intensity exercise, and lost 5 to 7 percent of their body weight. They reduced their chance of acquiring type 2 diabetes by 58 percent. Those randomized to treatment with metformin reduced their risk of acquiring type 2 diabetes by 31 percent.

Other study participants were randomized to a standard group taking placebos in place of metformin. They, and those who received metformin, also received diet and exercise information. A fourth arm of the study, treatment with the drug troglitazone combined with diet and exercise recommendations, was discontinued in 1998 due to the potential for liver toxicity.

The clinical trial ended a year early because the data had answered the main research questions, according to an NIH news release, which added, this “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.”

Forty-five percent of study participants 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 older 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,’ said DPP study chair, David Nathan, M.D., Massachusetts General Hospital. “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.”

Participants ranged from age 25 to 85, with an average age of 51. About 29 percent of the placebo group developed diabetes during the follow-up period of three years. In contrast, 14 percent of the diet and exercise arm and 22 percent of the metformin group developed diabetes.

“We simply don’t know how long, beyond the three-year period studied, diabetes can be delayed,” Nathan said. He and colleagues hope to follow the DPP population to determine how long the interventions remain effective. They will also analyze the data to determine whether the interventions reduced cardiovascular disease and atherosclerosis, major causes of death in people with type 2 diabetes.

Wing is co-directing a new 12-year, $180-million nationwide study of how weight loss affects cardiovascular disease, stroke and death in individuals with type 2 diabetes. She is also directing a study site at Miriam Hospital in Providence. For more information, call (401) 793-5599 or visit www.LookAHEADstudy.org.