MEDICINE / DIABETES : Exercise Reported Helpful in Postponement or Prevention

In a finding that could help millions of Americans at risk of developing diabetes in middle and old age, California researchers reported today that regular exercise such as swimming or bicycling may prevent or postpone the onset of non-insulin-dependent diabetes.

The finding, published in the New England Journal of Medicine, suggests a new weapon against adult-onset diabetes, a disease that affects 10 million to 12 million Americans and can cause many other conditions from heart disease to kidney failure and blindness.

“This is the first indication that there is a potential means to prevent the disease from occurring--with exercise,” said Richard Kahn of the American Diabetes Assn. “It certainly adds another piece of evidence that exercise is a valuable tool towards a healthy lifestyle.”

Exercise has long been a mainstay in the treatment of diabetes because of its role in encouraging blood sugar metabolism. But experts say the new study is the first to suggest strongly that exercise might slow or help avoid the onset of the disease.

Aerobic exercise is already known to lower a person’s risk of many other diseases including coronary artery disease, high blood pressure, stroke and obesity. Exercise is also recommended in the prevention of osteoporosis and in relieving the symptoms of depression.

“These are very important findings with important public health implications,” said Dr. David Leaf, medical director of the UCLA Healthy Hearts cardiac rehabilitation program. “If you look at cost-effective care, prevention is always the way to go.”

Non-insulin-dependent diabetes, also known as type II diabetes, tends to come on gradually in people over 40. The pancreas fails to produce enough insulin, the hormone that enables glucose to be absorbed into the liver and muscle cells to be converted to energy.

Type II diabetes is usually treated with dietary restrictions, exercise and oral medication. Possible complications of diabetes include damage to the retina and nerve fibers as well as atherosclerosis, hypertension and other cardiovascular problems.

In the new study, researchers at UC Berkeley School of Public Health and Stanford University School of Medicine studied retrospectively the cases of 5,990 men who graduated from the University of Pennsylvania between 1928 and 1947.

Each of the men had undergone a physical examination upon admission to college and had filled out questionnaires about his lifestyle and health in 1962 and 1976. Two hundred and two of them had developed type II diabetes during that later period.

The researchers found that men who reported getting regular exercise were significantly less likely to develop diabetes. And the more exercise they got, the less likely they were to come down with the disease.

The risk of diabetes dropped 6% for every 500 calories per week expended in physical activity--a level they said could be achieved by an hour of jogging at five miles an hour, bicycling at 10 miles an hour or swimming laps with light-to-moderate effort.

The “protective effect” of exercise was particularly dramatic for men at high risk for developing diabetes--that is, men who were overweight, had hypertension or had a family history of the disease, the group found.

“I am confident that exercise is having a tremendous impact,” said Susan P. Helmrich, a UC Berkeley epidemiologist and lead author of the study, who said she believed that women would benefit as much as men. “What the mechanism is, I’m not sure.”

Helmrich and others emphasized, however, that the results need to be confirmed in further studies.

The group theorized that exercise might protect against diabetes by helping maintain a proper lean-to-fat balance in body mass. Or, exercise might influence glucose metabolism, lowering glucose levels in the blood by enhancing the effect of insulin.

“I think what this points out is something that we intuitively knew, but it’s nice to see it statistically in a paper,” said Dr. Richard S. Beaser, medical director of the diabetes treatment unit at Joslin Diabetes Center in Boston.

“(That is,) that exercise is good for you and that people with a risk of getting diabetes will help themselves at least a little and perhaps a lot by exercising,” he said. “It’s just one more reason why we should get a little more active.”