In what is being called a landmark study of a national epidemic, doctors reported yesterday that modest diet and exercise are remarkably effective in delaying the onset of diabetes in people who are at risk.
People who lost an average of 10 pounds and engaged in simple exercise - such as walking 30 minutes a day - cut their odds of getting diabetes by 58 percent. Others who took a widely prescribed diabetes pill reduced their risk, too, but only by 31 percent.
"For the first time, we have shown that, yes, you can intervene and prevent the disease," said Dr. Christopher Saudek, president of the American Diabetes Association and director of the diabetes center at the Johns Hopkins School of Medicine.
The results come as public health authorities are expressing alarm at rising rates of diabetes - a phenomenon they blame partly on evidence that more Americans than ever are obese and leading sedentary lifestyles.
Although participants were counseled to count grams of fat and calories, doctors said weight-loss and exercise goals were within the reach of many Americans.
"For 30 minutes a day, five days a week, to go on a walk with your spouse doesn't seem to me to be asking the impossible," said the lead researcher, Dr. David Nathan of Massachusetts General Hospital.
The results were announced yesterday at the National Institutes of Health in Bethesda.
In the study, researchers at 27 medical centers enrolled 3,234 adults who took a blood-sugar test that showed them to be at increased risk for type-2 diabetes, the most common form. Most of the participants fell into well-known risk groups: they were obese, had family histories of diabetes or, in the case of women, had bouts of diabetes while pregnant.
16 million in U.S.
Diabetes afflicts 16 million Americans, and is the leading cause of kidney failure, amputations and new cases of blindness among adults. It is also a common cause of stroke and heart disease.
Some 15 million Americans have type-2 diabetes, a disorder in which the body develops a resistance to insulin, a hormone that is responsible for maintaining blood-sugar levels and enabling cells to produce energy.
Participants at 27 medical centers, including Hopkins, were randomly assigned to one of three groups - they were placed on diet and exercise, given the diabetes drug metformin, or given a placebo. Most stayed in the program for three years.
About 14 percent of the people placed on diet and exercise developed the disease, compared with 22 percent of those on the drug and 29 percent of those on placebo.
It remains to be seen whether the disease can be prevented for longer periods, Saudek said.
"We certainly want to know if this is going to be a persistent effect, or just a delay," he said. "If it is just a delay then we think we've done people a significant good. The more one delays the onset of diabetes, the less likely they are going to get the complications of diabetes."
Similar studies in China and Finland have shown that diet and exercise can prevent type-2 diabetes, but the U.S. trial was said to the first to show the preventive effects in an ethnically diverse population. Of the participants, 45 percent were from minority groups - African-American, Hispanic, Asian-American and Native American - that suffer disproportionately from the disease.
The results were equally impressive across all ethnic groups, Saudek said.
"This is a landmark study in the prevention of diabetes," said Dr. Alan Shuldiner, director of the Joslin Diabetes Center at the University of Maryland Medical Center.
Call for prevention
"It puts the onus on the medical community to recognize people at risk for the development of diabetes and to perform interventions to prevent it," said Shuldiner, who was not involved in the study.
Volunteers in the study took a blood test that measures a person's ability to process sugars. Those whose blood sugar was abnormal after drinking a sugar preparation were enrolled. Their condition, called impaired glucose tolerance, has no symptoms but puts a person at higher risk for diabetes.
Now, the diabetes association is weighing public health questions raised by the study: whether, for instance, to recommend that doctors screen people widely for impaired glucose tolerance.
The test costs less than $100, but is not used as a screening tool.
Whether the test comes into play as a screening tool, Shuldiner said, the role of diet and exercise is clear. The impact of obesity is particularly alarming in children, he said, among whom type-2 diabetes is suddenly on the increase.
The national trial included only adults, ranging in age from 25 to 81.
On average, people lost a maximum of 15 pounds, and maintained 10 pounds of weight loss, according to Saudek.
Katherine Horak, a Hopkins dietician, said patients were advised to cut dietary fat by reducing their consumption of dairy products, snack foods and fatty meats - and to eat more fish, lean meats, beans and fiber.
The goal was to lose 7 percent of body weight, meaning a person who started the study weighing 200 pounds would maintain a 14-pound loss.
"Even if some did regain weight, they did maintain their regular activity," she said. "They were still conscious of foods, still watching."
The study, which cost $174 million, was funded by the National Institutes of Health, the American Diabetes Association and several drug companies including Bristol-Myers Squibb, the makers of metformin.