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Why sitting may be hazardous to your health

Interrupting sedentary time with short bouts of exercise may diminish the dangers of inactivity.


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Every time we think we have a handle on all the things that are bad for us, another one is added to the list. A few years ago, researchers put inactivity on the roster of major health risks. “Everybody knows smoking is bad for your health. But what isn’t common knowledge is that physical inactivity is as powerful a risk factor as smoking,” says Dr. I-Min Lee, professor of medicine at Harvard Medical School. Dr. Lee, who has studied the effects of exercise for more than a decade, was one of the first to identify inactivity as a health hazard.

Dr. Lee was among the experts contributing to a special issue on health and exercise of the British journal The Lancet commemorating the 2012 Olympic Games in London. She and her colleagues pored over reports from scores of large observational studies conducted worldwide in which participants answered questions about their lifestyles, including their levels of physical activity, and were then followed over a period of years to see how they fared. When the researchers compared the health outcomes of participants who were inactive—those getting less than 150 minutes a week of moderate exercise—to those who got more exercise, they found that inactivity alone counted for an increased risk of breast and colon cancers as well as heart disease and diabetes. They computed that inactivity was responsible for more than five million deaths a year worldwide, about the same as the number of deaths attributable to smoking.

What we’ve learned since

In the past few years scientists have been working to determine exactly how inactivity affects our health. Here’s what they’ve found:

Older women are sedentary two-thirds of their waking hours. In 2013, in The Journal of the American Medical Association, Dr. Lee and her colleagues reported results of a study of a group of more than 7,200 participants in the Women’s Health Study. The women, whose average age was 71, wore activity trackers during their waking hours for a week. The researchers determined that the women were sedentary for about two-thirds of their waking hours, but their bouts of sitting were broken up an average of nine times per hour. However, total sitting time increased and the number of breaks per hour decreased with age and body mass index (BMI).

Breaking up sitting time has benefits. A 2012 study in Diabetes Care indicated that interrupting sitting time with short bouts of walking lowers blood sugar (glucose) and insulin levels in overweight or obese adults. A 2015 study, albeit in men, demonstrated that short bouts of activity improved the function of blood vessels.

Exercise can compensate for even long bouts of sitting. In an analysis of 16 studies that tracked exercise and sitting over time, Dr. Lee and colleagues concluded that daily exercise may erase the detrimental effects of sitting. The team determined that 60 to 75 minutes of moderate exercise daily eliminated the risk of an early death conferred by eight hours of sitting. They reported their findings in August 2016 in The Lancet.

The bottom line

It can be hard to remember to get up and move, especially when you’re engrossed in a good book or television program. You can wear an activity tracker with an alarm to alert you if you haven’t taken enough steps in the past hour. Setting aside an hour a day for a brisk walk should also work.

Binge watchers, beware: TV viewing is also a health hazard

Several studies have indicated that hours spent watching television are an independent risk factor for degenerative diseases and early death. Dr. Lee speculates that people usually sit while watching TV and are also more likely to remember the programs they watch than to recall how much time they spend sitting.

A simple solution is to time your exercise to coincide with your TV viewing. If you don’t have a stationary bike or treadmill in your living room or den, try jogging in place or pacing around the room while you watch the news or your favorite series. You may be surprised at how many steps you log.

Posted by: Dr.Health

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