June 20th, 1999
Exercise Can Reduce Diabetes Risk
By Ira Dreyfuss
Get away from the television, go out and take a walk, and you can reduce your
risk of developing diabetes, a study finds. "You need to increase your
physical activity level, and you want to reduce your sedentary behavior, because
the beneficial effect of exercise may be offset by your sedentary behavior if
you spend too much time on the couch watching TV,’’ said Dr. Frank B. Hu, a
researcher at the Harvard School of Public Health.
The study, presented Saturday at the American Diabetes Association meeting
in San Diego, is the first to find that the risk rises directly with hours spent
watching television, Hu said.
Previous studies have found that the risk of obesity, which itself is a risk
factor for diabetes, rises with more hours in front of the tube. This study
finds the disease is more likely to develop in constant viewers even when obesity
and other factors are taken into account.
The findings are based on 10 years of data for those aged 40-75 in the Health
Professionals Follow-up Study. The dentists, podiatrists, pharmacists, optometrists
and veterinarians completed periodic questionnaires on their health and their
According to Hu’s data on 37,918 men, 1,058 developed type II diabetes, a condition
in which the pancreas may produce less insulin or the body’s cells become less
sensitive it. Insulin carries the sugar glucose into the cell, where it is used
Compared with men who watched little or no TV, men who spent 21-40 hours a
week or even more watching TV had more than twice the likelihood of getting
diabetes, the study found.
"A substantial number watch 21 to 40 hours per week - about four or five
hours a day,’’ Hu said. The risk was close to three times higher in men who
watched more than 40 hours a week. It was no more than two-thirds higher in
men who watched 10 hours or less.
The study indicates that the risk goes up roughly in tandem with the amount
of TV watched, Hu said. The study did not look at why TV watching raises the
The increase may arise because sitting eliminates even normal activity, commented
Dr. William H. Dietz, director of the Division of Nutrition and Physical Activity
at the federal Centers for Disease Control and Prevention.
If so, just turning off the set may not be enough to lower the risk, Dietz
said. ``If you replace TV watching with reading, there may not be a health benefit,’’
he said. On the other hand, TV watching may be a marker for other lifestyle
factors that could be the underlying causes, Dietz said.
The study also found that even fairly comfortable levels of physical activity
can reduce the risk of diabetes, Hu said. That’s important because most previous
researchers had focused on vigorous activity, such as running, he said.
The Health Professionals study looked at several forms of activity, including
walking and running, and converted them statistically into levels of energy
As expected, those who burned the most energy, such as those who ran almost
every day, got the most benefit. The most active exercise group had about 50
percent of the diabetes risk of those who were sedentary.
But even those who did about 20 minutes of walking on most days had a risk
reduction of more than 20 percent, Hu said. And those who did the 30 minutes
of moderate activity on most days, as current federal guidelines recommend for
good health, had a risk reduction of more than 30 percent.
"The more you exercise, the less the risk,’’ Hu said. "Even light
exercise is better than being completely sedentary.’’ The exercise findings
fit a research trend that shows the risk of developing diabetes and many other
diseases goes down as the level of exercise goes up, commented Dr. Jody Wilkinson,
a research physician at the Cooper Institute of Aerobics Research, Dallas.
"If you look at people who meet even minimal guidelines, they are going
to benefit from that,’’ he said. "The majority of us aren’t even getting
the minimal levels.’’
Doctors prescribe physical activity for diabetics, but don’t give it a high
enough priority, in part because patients are more likely to take their medication
than to get their exercise, Wilkinson said. However, the Harvard study indicates
"it doesn’t take a regimented exercise program to make a difference,’’