New Study: How Does Sitting Shorten Your Life?

How Does Sitting Shorten Life?
Looking to extend your life (and improve quality of life) by 3 or 4 years?

A new study says sitting 3 or more hours a day cuts your life by 2 years.  Watching TV makes things even worse: If you watch for two hours a day, your life-expectancy drops by another 1.4 years.

"Sitting is a risk factor, not a disease," says study author Dr. Peter Katzmarzyk, associate executive director for population science at Pennington Biomedical Research Center at Louisiana State University System in Baton Rouge. "It's comparable to obesity, and it's almost to the level of smoking. We need to turn that around and engineer sitting out of our lives."

For Katzmaryk's study, researchers pulled data from five relevant research papers that involved nearly 167,000 adults. The researchers then came up with "population attributable fraction (PAF)" estimates that measure theoretical effects of how sitting would affect an entire population. Those estimates were used to calculate the number of deaths associated with sitting down, leading researchers to conclude that restricting sitting to fewer than three hours a day could tack on two more years of living. They also found cutting television viewing to less than two hours each day could lead to a 1.38-year gain in longevity.

Why is Sitting Bad for You?

Here's what happens when you sit:  Electrical activity in the muscles drops — "the muscles go as silent as those of a dead horse," [inactivity researcher Marc] Hamilton says — leading to a cascade of harmful metabolic effects.

Your calorie-burning rate immediately plunges to about one per minute, a third of what it would be if you got up and walked.

Insulin effectiveness drops within a single day, and the risk of developing Type 2 diabetes rises. So does the risk of being obese.

The enzymes responsible for breaking down lipids and triglycerides — for "vacuuming up fat out of the bloodstream," as Hamilton puts it — plunge, which in turn causes the levels of good (HDL) cholesterol to fall.

In short, sitting makes you fat, weak, and more likely to get sick.

You can't counteract the harmful effects of sitting by exercising once in a while. If you exercise a lot but also sit around a lot, you'll still have a shorter lifespan than people who don't sit so much.

But here's some good news:

You don't have to start running marathons to offset all that sitting. You also don't have to get a treadmill at the office and sweat all day. You just have to get up every hour or two and walk around for a while. Or, alternatively, you just have to stand instead of sit.

The findings are published in the July 9 issue of BMJ Open.

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