Invasion of the killer chairs! When sofas attack! No, these aren’t titles of bad horror movies or the latest video games. It’s a reflection of what our lifestyle — one where we sit too much — is doing to us.

According to research, Americans spend 13 hours on average a day sitting down, and James Levine, an endocrinologist at the Mayo Clinic and author of Get Up!, researches what all this sitting is doing to us. He argues that chairs are lethal. They are literally killing us. The lack of movement slows down our metabolism and contributes to obesity, heart disease, arthritis, diabetes, and stress.

The good news is that simple natural movement throughout the day — not an hour of vigorous activity at the gym — can have a dramatically positive effect on health.

In one experiment, Levine compared obese and lean people who lived in similar environments and who shared similar lifestyles, diets, and jobs. They were all given “magic underwear” — an undergarment with motion sensors to collect data about how much they moved throughout the day. Not surprisingly, the obese people sat 2.25 hours longer than their thinner counterparts.

To further explore the effect of natural movement — what Levine terms “nonexercise activities” — on weight gain, Levine and his team designed the Great Gorging Experiment. Lean participants were asked to consume 1,000 more calories than usual every day for eight weeks. In spite of the overeating — a total of 56,000 extra calories over the course of the study — some participants didn’t gain any extra body fat. How did they stay skinny? According to data generated from the magic underwear, they simply moved around a lot more. What is interesting is that none of them said they made a conscious effort to do so.

In contrast, those who gained body fat in the study did not increase their movement. Instead of moving more, they reclined. They remained stuck to their chairs.

As part of a chair-free lifestyle, Levine came up with the idea of a treadmill desk 10 years ago. Studies show that people who use them are less stressed, have lower blood pressure and cholesterol and are skinnier. I got one last year and have found it to be life changing. Not only do I feel less tense at the end of the day, but I am more focused and productive.

As Levine writes:

We live amid a sea of killer chairs: adjustable, swivel, recliner, wing, club, chaise longue, sofa, arm, four-legged, three legged, wood, leather, plastic, car, plane, train, dining and bar. That’s the bad news. The good news is that you do not have to use them.

In that spirit, if you are reading this article sitting down, please stand up.