We've got some bad news to tell you. Normally, we'd advise you to take a seat first, but, you see, that's just the problem: If a number of recent studies are to be believed, hours of daily sitting are slowly killing you.
The most recent research, published this week in the online journal BMJ Open, claims that sitting for more than three hours a day can cut one's life expectancy by two years. Watching television for more than two hours a day adds to the effect, potentially decreasing life expectancy by another 1.4 years.
But here's what's most disturbing: The effects of hours of sitting are not entirely offset by one's regular exercise. As the new study's co-authors put it, "One can be both sedentary and physically active." For example, an office worker who jogs regularly but is otherwise chained to his or her desk for eight-to-ten hours a day is still at risk.
The study, co-authored by Dr. Peter Katzmarzyk of the Pennington Biomedical Research Center in Baton Rouge, analyzed five long-term studies of the behavior of almost 167,000 Americans. Because those studies relied in part on participants' self-reporting, it's expected that people may have understated the amount of time they sat watching TV. The study eliminated subjects who had medical conditions that would make them more likely to remain sedentary for long periods.
"This study elevates the importance of sedentary behavior as a risk factor for premature mortality," the research team wrote. "The risks associated with sedentary behavior appear to be on par with the risks associated with smoking and obesity."
"Excessive time spent in sedentary behavior is undoubtedly having an impact on public health," according to the researchers, especially since government research shows that adults spend, on average, 55 percent of the day in sedentary pursuits. "A significant shift in behavior change at the population level is required to make demonstrable improvements in life expectancy."
Sedentary behavior has long been linked to obesity and poor heart health. A study released by University of South Carolina researchers a year ago found that men who had more than 23 hours of total sedentary behavior each week were 64 percent more likely to die of cardiovascular disease than those who spent less than 11 sedentary hours a week. People with sedentary lifestyles also appear more prone to contracting colon, rectal, kidney, and pancreatic cancer.
In an interview with National Public Radio, epidemiologist Steven Blair, a co-author of the South Carolina study, said that many of its participants exercised regularly, even achieving the 150 minutes of weekly moderate aerobic exercise prescribed for adults by the federal Centers for Disease Control (CDC). (Studies have shown that fewer than half of all adults meet this guideline.) And, to be sure, the men in his study who were the most physically active had "notably lower rates" of cardiovascular death than those who were primarily sedentary. Still, he warned, consistent movement and avoidance of lengthy sedentary periods is crucial for everyone. Consider: If you walk 30 minutes a day and sleep 8 hours each night, "that still leaves 15.5 hours," Blair said, and if most of those hours are spent seated, you can still face an elevated health risk.
What is so dangerous about sitting? It's more than the lack of exercise, experts say. When we sit for long stretches of time, our major muscle groups, such as our backs and legs, become inactive. When those muscles are not contracting, studies have shown, our body's metabolism slows down, which can cause our cholesterol and blood sugar levels to rise, and over time, make our waists more likely to expand — all of which increase our chance of contracting heart disease or diabetes.
What You Can Do
If you work full time in an office, consider encouraging your employer to look into installing standing or treadmill desks so you can stand or even walk while you work. Or start sitting on an exercise ball instead of a desk chair, which will help keep your core abdominal muscles engaged and burn more energy than sitting on a chair. But no matter what you sit on, make sure to get up from that seat at least once an hour to stretch your legs or walk down the hall to talk to co-workers. And twice a day, find 10-minute periods to get out of your cubicle or office altogether, either for a brisk walk outside or up and down the stairs of your building. If you can bike or walk to work instead of driving, that will help, too.
At home, consider reading books or magazines, or using your laptop, while standing at a counter instead of sitting on the couch. And make a point of taking all of your phone calls standing up so you can multitask by walking around your home while you talk. If you're watching TV, get up and stretch or walk around during every commercial break. If you record shows, get up and move when the ads come on instead of fast-forwarding. That should give you at least four breaks an hour.