Diet and exercise best medicine in preventing diabetes

A large-scale study found that lifestyle changes are most effective at delaying the onset of type 2 diabetes, followed by metformin, now used in treatment.

By Susan J. Landers, amednews staff. Aug. 27, 2001.

Washington -- Weight loss of 10 to 15 pounds and 30 minutes of brisk walking five days a week may be all that separates a patient who has type 2 diabetes from one who does not.

Results from a large, multisite clinical trial show that at least 10 million Americans now at high risk for type 2 diabetes -- by far the most prevalent type -- can sharply lower their chances of getting the disease with diet and exercise.

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"In view of the rapidly rising rates of obesity and diabetes in America, this good news couldn't come at a better time," said Dept. of Health and Human Services Secretary Tommy Thompson at the Aug. 8 unveiling of the study results.

Among those cheering the findings was Charles M. Clark Jr., MD, chair of the National Diabetes Education Program, and professor of medicine and pharmacology at Indiana University's Diabetes Research and Training Center in Indianapolis.

"Two things have happened with this study," Dr. Clark said. It proves the hypothesis that lifestyle changes are important and it shows that such changes can be made, he said.

"There is a twofold message for the primary care doctor, one that it works and two you can do it," he said. Dr. Clark was attending a meeting of the Diabetes Mellitus Interagency Coordinating Committee where the study's findings were detailed.

Dr. Clark recommended that physicians work within their communities to develop effective weight-loss and exercise programs at YMCAs or community centers.

The findings came from the Diabetes Prevention Program, a clinical trial with an ethnically and racially diverse group of 3,234 participants ranging in age from 25 to 85.

The study's goal was to compare the effectiveness of diet and exercise at delaying the onset of diabetes to treatment with the oral diabetes drug metformin hydrochloride, known by the brand name Glucophage, manufactured by Bristol-Myers Squibb Co.

The participants were uniformly at high risk of type 2 diabetes -- all had impaired glucose tolerance as measured by an oral glucose tolerance test, and all were overweight.

The trial was ended after three years, a year early, because the benefits of diet and exercise had been so clearly proven.

Big improvements

Participants randomly assigned to the lifestyle change group reduced their risk of getting type 2 diabetes by 58%. Older people who made the lifestyle changes did even better and reduced their risk by 71%.

The participants who took 850 mg of metformin twice a day reduced their risk of getting type 2 diabetes by 31%. The drug was approved in 1995 to treat type 2 diabetes but not to prevent the disease.

The lifestyle group exercised 30 minutes a day, usually by walking briskly, and, following a low-fat diet, lost 5% to 7% of their body weight, or about 10 to 15 pounds, said researchers.

A third group was given placebo pills instead of the metformin.

A fourth group that was being treated with the drug troglitazone combined with standard diet and exercise recommendations was discontinued in June 1998, when the drug was withdrawn from the market because of the possibility of liver toxicity.

About 29% of the group given the placebo developed diabetes during the average follow-up period of three years. In contrast, 14% of the diet and exercise group and 22% of the metformin group developed diabetes.

Although smaller studies in China and Finland have shown that diet and exercise can delay type 2 diabetes in at-risk people, this trial demonstrated the effectiveness of the approach for America's diverse population.

Researchers made an effort to recruit participants from minority populations that suffer disproportionately from type 2 diabetes: African Americans, Hispanics, Asian Americans, Pacific Islanders and American Indians. Of the 3,234 participants, 45% were minorities.

The trial also included many other people known to be at high risk for type 2 diabetes, including people age 60 and older, women with a history of gestational diabetes and individuals 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% prevalence of diabetes, reducing their development of diabetes by 71%," said David Nathan, MD, who chaired the study group.

"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," he said.

Dr. Nathan said the researchers hope to continue to follow the participants to see how long diabetes can be delayed.

Secretary Thompson said he thought prevention of disease was key to bringing down the high cost of the serious illnesses that accompany diabetes. "It seems wrong to wait for people to get sick and then spend thousands to get them well," he said.

Meanwhile, Rep. Diana DeGette (D, Colo.), co-chair of the House Diabetes Caucus, faulted the Bush administration for proposing to cut $6 million from the Centers for Disease Control and Prevention's diabetes education and prevention programs.

"Now that we know that we can prevent many cases of type 2 diabetes through diet and exercise, we need to get the word out, especially to those people most at risk," DeGette said. "The CDC's programs are aimed at doing precisely that."