Is Your Desk Chair Killing You?

If you’re like most people, you do a lot of sitting all day. You sit in front of your computer. Then get into your car for a long commute home from work. What’s next? More sitting: at dinner and in front of the TV. Scientists are finding that this stationary behavior is putting us at risk and sabotaging our other efforts to stay healthy. In fact, if you think your daily exercise routine will protect you from time spent in a chair or on a couch, think again.

The most recent study on this topic: an analysis of 505 men and women attending a diabetes-screening program. By using a questionnaire that determined physical activity, researchers asked the subjects to report the amount of time they spent sitting on weekdays. The researchers then measured glucose levels, fasting insulin and inflammatory markers such as C-reactive protein (CRP), adiponectin, and interleukin-6 (IL-6). They also measured levels of leptin, a hormone that controls how much you eat.

In the female subjects, increased sitting time caused significant imbalances in fasting insulin and imbalanced inflammatory responses. Leptin levels also increased in the sedentary women, a result that suggests even being a temporary coach potato can cause your hunger levels to soar. The associations for women remained significant even after researchers adjusted for total moderate- to vigorous-intensity physical activity.¹

The researchers conclusion? “Total self-reported weekday sitting time was associated with biomarkers linked to chronic low-grade inflammation and poor metabolic health in women, but not men, independent of physical activity.”

In 2010, a study in the journal Circulation created a lot of buzz around this same topic. Researchers examined 8,800 adults 25 years of age or older. What they found is enough to make all of us turn off the TV. Because the study showed that each extra hour of television watching per day was linked to an 18 percent increase in deaths from heart disease and an 11 percent increase in overall mortality. And people who watched TV for at least four hours a day? The statistics were even more startling. They were 80 percent more likely to die of cardiovascular disease than those who watched two hours or less—and 46 percent more likely to die of any cause.²

Even more shocking: the increase in heart and mortality risk occurred even in people who exercised—and were independent of healthy eating habits as well! And other studies reached similar conclusions, reporting significant associations between total sitting time with blood glucose, blood lipids, and adiposity, even in people who performed moderate to vigorous exercise several times each week.² One study of Japanese men and women showed an increase in all-cause mortality in men who reported sitting for eight hours per day or more compared to those reporting sitting for less than three hours per day.³

Why is sitting so harmful to health? One possible answer comes from animal studies, which show that a sedentary lifestyle can reduce our body’s ability to process fats. Leg muscles tend to increase production of a fat-processing molecule known as lipoprotein lipase when you’re standing or walking around. Sitting means this molecule is in shorter supply—spelling disaster for the body because low levels of lipase lipoprotein are associated with health concerns such as suboptimal heart health.

But lipase lipoprotein isn’t the only beneficial substance produced during the flexing of muscles. Contracting the muscles produces other compounds that help the body properly use and store sugars and fats.

So the problem isn’t just exercising too little. It’s sitting too much.

The good news: There are easy ways to take a break from sitting. Here are some approaches to ensure your muscles are flexed throughout the day:

• Take time out from your computer, desk and television to walk and move around.
• Stretch while you’re at your desk.
• Consider buying a stand-up desk. If that’s not possible, stack books, a box, crate or something on your desk so that you can type standing up, at least some of the time.
• Read books, papers, memos, etc. while standing.
• Conduct meetings while standing.
• Watch TV while exercising on a stationary bike.

References:

1. Yates T, Khunti K, Wilmot EG, Brady E, Webb D, Srinivasan B, Henson J, Talbot D, Davies MJ. Self-reported sitting time and markers of inflammation, insulin resistance, and adiposity. Am J Prev Med. 2012 Jan;42(1):1-7.

2. Dunstan DW, Barr ELM, Healy GN, Salmon J, Shaw JE, Balkau B, Magliano DJ, Cameron AJ, Zimmet PZ, Owen N. Television Viewing Time and Mortality. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Circulation. 2010;121:384-391.

3. Inoue M, Iso H, Yamamoto S, Kurahashi N, Iwasaki M, Sasazuki S, Tsugane S. Daily total physical activity level and premature death in men and women: results from a large-scale population-based cohort study in Japan (JPHC study). Ann Epidemiol. 2008;18: 522-530.