Exercise Is a Habit; Here's Why to Pick It Up
strikingly large number of Americans have failed to catch the exercise bug, and the effects are showing up not only in their expanding girth but also in their health and death statistics.
American women are particularly sedentary. According to the 2000 National Health Interview Survey, 72 percent of women and 64 percent of men get no regular exercise.
Yet as Dr. I-Min Lee of Brigham and Women's Hospital in Boston has noted: "Physical inactivity increases the risk of developing many chronic diseases, including coronary heart disease, stroke, Type 2 diabetes and certain cancers. Such sedentary behavior is also associated with higher body weight, and obesity increases the risk of many of the same chronic diseases."
Why, in the face of decades of propaganda, aren't more women moving in ways that can protect their mental and physical well-being?
One reason may be that the early prescriptions for protective exercise vigorous aerobic activity for at least 20 minutes, at least three times a week did not suit sedentary people, who shun heavy sweating and breathlessness.
Another reason might be that the three-times-a-week approach failed to establish a routine that fitted into one's daily life.
Now all that has changed. In the last decade, dozens of studies have shown that exercise need not be vigorous to confer a significant health benefit.
Although more is better, up to a point, the current recommendation moderately vigorous activity for 30 minutes a day on most days reflects recent findings that one need not become a jock to reap many of the rewards of regular activity.
Although for weight control an hour a day of moderate-intensity activity is preferable, even half that can reduce the risk of heart disease and strokes, diabetes, and cancers of the breast and colon.
Notice that I said regular. Physical activity should be programmed into daily life, just like eating, sleeping and brushing your teeth, so that you really miss it when circumstances force you to skip a day or two now and then.
One of the best ways to make exercise a daily habit is to find one or more activities that you enjoy and one or more companions who will participate in them with you.
What gets me out each morning at 6 or 7 o'clock to walk briskly for an hour, rain or shine? The knowledge that my friends will be waiting for me on the corner, not to mention the magnificent sunrises, birds, blooms and bunnies we often encounter.
I often remark, "Look at what the stay-a-beds are missing!"
Two studies published last week in The Journal of the American Medical Association may provide the motivation many women need to get moving and stay moving.
One study, directed by Dr. Anne McTiernan of the Fred Hutchinson Cancer Research Center in Seattle, examined the risk of breast cancer among 74,171 postmenopausal women enrolled in the Women's Health Initiative study.
Although a number of previous studies found that physically active women had a decreased risk for breast cancer, little was known about what kinds of activity and how much was needed to be protective.
The new study, which followed the women for an average of nearly five years, found that those who engaged in the equivalent of 75 to 180 minutes a week of brisk walking had 18 percent less risk of developing breast cancer than inactive women.
The risk continued to decline, but only slightly, for women who did up to 10 hours of brisk walking or its equivalent, although other studies have suggested that the degree of protection is directly related to the amount of activity.
Not only was current physical activity protective. Women in the study who had been physically active at ages 35 and 50 also experienced a reduced cancer risk, the authors noted.
Furthermore, those who were using postmenopausal hormones, which increase breast cancer risk, were less likely to get breast cancer if they were physically active.
The authors wrote: "For those women who choose to continue taking hormone therapy for control of menopausal symptoms or for prevention of osteoporosis, it will be welcome information that a simple modification of lifestyle to increase physical activity can reduce their risk of breast cancer."
In concert with other findings about the role body fat plays in increasing the risk of breast cancer, the greatest reduction in breast cancer risk associated with regular exercise was seen in lean women.
And that brings me to the second new study, directed by Dr. John M. Jakicic of the University of Pittsburgh's Physical Activity and Weight Management Research Center.
This was a yearlong randomized trial, the gold standard of research, conducted among 201 seriously overweight sedentary women.
All participants were instructed to reduce their caloric intake by an average of 31 percent to a range of 1,200 to 1,500 calories a day and to limit fat intake to 20 to 30 percent of daily calories.
The women in the study were then randomly assigned to one of four different exercise regimens: vigorous intensity, high duration; moderate intensity, high duration; vigorous intensity, moderate duration; and moderate intensity, moderate duration.
All four groups lost a significant amount of weight, but there was no real difference between the various exercise groups in how much they lost or how well they maintained the loss.
All the participants also experienced a significant improvement in cardiovascular fitness, and again there was no real difference in benefit based on which exercise group the women were in.
Those in the "moderate duration" groups exercised 40 minutes a day, or 200 minutes a week, while those in the "high duration" groups exercised 60 minutes a day, or 300 minutes a week.
In an accompanying editorial, Dr. Lee pointed out that "other studies have shown that decreased rates of coronary heart disease and premature mortality begin to occur at even lower levels perhaps at one to two hours per week of moderate-intensity leisure-time activity."
The women who did vigorous exercise did not lose more weight than those who exercised at a more moderate intensity. But just as one might expect, more exercise was better than less.
The women who exercised less than 150 minutes a week had an average weight loss of 4.7 percent; those who exercised 200 minutes or more each week lost 13.6 percent of their starting weight.
This suggests that for weight loss and maintenance, exercising moderately for an hour a day is more effective than shorter exercise sessions.
Likewise, previous studies have indicated that an hour a day of moderately intense exercise is more effective at preventing heart disease than half an hour. But perhaps more important than duration is consistency.
As Dr. Paul D. Thompson, an expert on exercise and heart disease at Hartford Hospital, has noted, "People should try to exercise daily to minimize the number of days missed, and because many of the effects of physical activity on risk factors are, in part, acute effects of recent exercise."