I firmly believe the greatest risk to my physical and mental health right now is the amount I sit.

The negative health effects of sitting have been known for some time, but stole headlines a few years ago when James Levine, a professor of medicine at the Mayo Clinic coined the phrase “sitting is the new smoking” and said “the chair is out to kill us” in an interview with the LA Times.

It’s estimated that in North America, half of our waking hours are spent sitting down. “Sitting is more dangerous than smoking, kills more people than HIV, and is more treacherous than parachuting. We are sitting ourselves to death,” says Levine.

The harmful physical effects of sitting are well known. Sitting or lying down for too long increases your risk of obesity, chronic health problems, such as heart disease, diabetes and some cancers and can shorten your life span.

What was even more startling as I researched this was learning that getting the recommended 30-60 minutes of exercise a day won’t help. You can’t offset 10 hours of stillness with one hour of exercise.

Here’s the science behind it. Metabolism slows down 90 percent after 30 minutes of sitting. The enzymes that move the bad fat from your arteries to your muscles, where it can get burned off, slow down. The muscles in your lower body are turned off. After two hours, good cholesterol drops 20 percent.

And that’s only half of it. Sitting too much also has an impact on your mental health.

Dr. Alan Schlechter, a professor on the science of happiness at New York University says the way we tell our brain to grow is to move. We are meant to move, and when we sit down for more than 20 minutes, our body and brains shut down.

There is one simple solution to fighting the chair. Get up and move every twenty minutes.

As one expert said, “Just getting up for five minutes is going to get things going again. These things are so simple they’re almost stupid.”

This week, I’m taking up my armrests and fighting the chair in the interests of my own physical and mental health. I’m going to start booking walking meetings at work, move around more, take the stairs, watch less TV at night and get up and move every 20 minutes. Who’s with me?