Mounting evidence suggests that sitting for long periods increases the risk of obesity, diabetes, cancer and early death, even for people who exercise daily. And yet Americans now sit more than they sleep, spending an average of 10 hours a day in a car, at work and in front of a television. Older adults are the worst offenders, according to federal government statistics: Almost three-quarters are sedentary, and more than four in 10 get no leisure-time physical activity at all.
See also: Walking: The easiest exercise.
To reduce your cancer risk, the American Institute of Cancer Research is urging Americans to add mini-breaks from sitting to a daily regimen of getting at least 30 minutes a day of moderate-to-vigorous exercise.
"If you reduce sitting by five minutes an hour, at the end of a long day, you've shaved an hour off your total sitting time," says Alpa Patel, M.D., senior epidemiologist with the American Cancer Society. That advice applies as well to "active couch potatoes," who hit the gym or take that daily brisk walk, because some research indicates daily exercise is not enough protection from the harmful effects of a sedentary lifestyle.
Women who reported sitting more than six hours a day outside of work had a 34 percent higher risk of death than those who sat fewer than three hours daily, according to a recent American Cancer Society study. This was true even for women who exercised regularly.
In a University of South Carolina study, even physically active men were 64 percent more likely to die of heart disease if they sat more than 23 hours a week in front of the TV, compared with those who sat 11 hours a week or less.
Prolonged sitting appears to have powerful metabolic consequences, disrupting processes that break down fats and sugars in the blood. In animal studies, inactive mice and rats quickly develop higher blood fats and lower levels of good cholesterol, which together increase the risk of cardiovascular disease. An Australian study suggests a link between a sedentary lifestyle and several key biological indicators of cancer risk, including insulin resistance, inflammation and body weight.
Older adults will remember pre-soccer-mom days of walking to school, biking to baseball practice, hanging up laundry and washing the dishes. Technology, experts say, has engineered physical activity out of daily life. With the advent of personal computers and cable TV, not to mention remotes and garage door openers, there is scarcely a reason to get out of your seat.
Physical activity in the workplace has fallen, too, according to a recent study. Fifty years ago, more than half of American jobs involved moderate physical activity, often in manufacturing or agriculture, reports Pennington Biomedical Research Center in Baton Rouge, La. "Today it's less than 20 percent — we're tied to our desks," says Tim Church, M.D., a Pennington professor and the study's lead author.
Last year, registered dietitian Jill Weisenberger wrote a book and started worrying about sitting too much. "I jog every morning, but what about the other 23 hours a day? I've read that sitting makes the blood vessels less elastic, and I didn't want to be a jogger and a dietitian with heart disease," says Weisenberger, 50, of Yorktown, Va. At home she began walking a circuit while cooking dinner. Then she bought a desk equipped to fit over a treadmill and now logs 30 to 35 miles a week walking at 1.4 miles per hour. "I can type, read email, surf the Net — anything except have pretty handwriting," she says.
The Cancer Society's Patel stands during conference calls, uses a printer in another office, and eschews email and the telephone to walk over to a colleague's office. She also sits on an exercise ball. "It's called 'active sitting.' If you slouch you fall off," she says. She takes a brisk 20-minute walk at lunch, adding longer walks before or after work. By reducing sitting time and ramping up physical activity, Patel also lost 40 pounds in six months.
Also of interest: 10 tips for smart snacking. >>
Elizabeth Pope is a writer based in Portland, Maine.
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