Regular exercise cuts diabetes risk.

An active lifestyle, including moderate-to-vigorous exercise, may prevent development of Type II diabetes, the sugar-processing disorder that generally strikes after age 40, according to a study published this week. The new finding may provide couch potatoes further incentive to turn off the TV and turn onto regular exercise, such as running, swimming or tennis.

Non-insulin-dependent diabetes -- the Type II form -- often involves insulin resistance, a disorder in whichs the body usually makes adequate amounts of insulin but its cells respond sluggishly to the hormone. The presence of insulin normally spurs cells to sop up sugar circulating in the bloodstream. This sugar removal is not as effective in Type II diabetics, so their blood sugar levels rise--a problem that can lead to life-threatening complications.

Previous studies indicated that physical exercise can counteract insulin resistance and improve the body's ability to metabolize sugar. Indeed, such reports led physicians to advise people diagnosed with Type II diabetes to begin a regular fitness regimen. Scientists also suspected that fitness might stave off Type II diabetes in healthy people, yet data on this were less than compelling.

Now a report in the July 18 NEW ENGLAND JOURNAL OF MEDICINE adds considerable evidence to the theory that regular exercise prevents Type II diabetes. "It's a very exciting paper," comments diabetes researcher Edward S. Horton, of the University of Vermont College of Medicine in Burlington.

Epidemiologist Susan P. Helmrich of the University of California, Berkeley and her colleagues analyzed data collected from 5,990 initially non-diabetic men who had attended the University of Pennsylvania between 1928 and 1947. In 1962, researchers sent the men a questionnaire that asked about fitness habits, including sports such as jogging and tennis, and other aerobic activities such as walking up stairs. They then calculated the amount of energy expended per week on such leisure activities. When the researchers queried the volunteers again in 1976, they learned 202 had developed Type II diabetes.

Now, using a statistical method that accounts for known diabetes risk factors as well as physical activity, the California teams finds evidence that compared with the most active men in the group, the most sedentary faced twice the risk of developing Type II diabetes during the 14-year study period. The couch potatoes had reported engaging in less than one hour of sustained exercise per week in 1962, while the most active men said they logged seven hours or more. Even moderate activity, however, such as a daily brisk walk, seems to shave the risk of Type II diabetes.

People with a family history of Type II diabetes or with other diabetes risk factors gained most from regular exercise: Compared with their sedentary peers, the most active men in this high-risk subgroup showed a 42 percent decrease in their risk of Type II diabetes, the team found.

"We are basically a nation of couch potatoes. Most people watch sports instead of playing sports," says Helmrich, a marathon runner. These "very dramatic" new data indicate most Americans would benefit from a lot more exercise, she observes.

This study also confirms a prevailing theorty that Type II diabetes is a "lifestyle disease" -- one that's been linked to the sedentary lifestyle and high-calorie diets typical of most industrialized societies, adds coauthor Ralph S. Paffenbarger Jr. of Stanford University, another marathon runner.

Many factors, including obesity, family history and age can increase the threat of Type II diabetes. However, the new study suggests inactivity poses an independent risk factor for this disease. Comments Rena Wing, a diabetes researcher at the University of Pittsburgh, this finding may represent good news for at-risk Americans: "You can't modify your age. You can't modify your parental history. But, you can increase your activity."