Updated April 05, 2015.

It sounds overly dramatic, I know. But the fact is, sitting 6 to 8 hours per day or more is one of the most sneaky ways your health can turn sour. And by sour, I mean ripening you up for life-changing, and life-ending, conditions such as type 2 diabetes, heart disease, cancer--especially colon cancer, depression, and obesity, and I haven't even listed any of the muskuloskeletal problems we've long known about, such as enough specific varieties of shoulder, neck, and back pain issues to fill a robust restaurant menu.

The news gets worse. Studies have now shown that even people who exercise daily for 30 minutes, yet still spent 6 to 8 hours per day sitting, still developed the same health problems. To put it bluntly, 30 minutes at the gym simply aren't enough to negate the damages you did to your body sitting at your desk at work all day.

If you're not already, do yourself a favor and stand up while you read the rest of this article. Here's why...

Sitting, for 1 Minute

As soon as we sit, electrical activity in the leg muscles shuts down. The electrical shut off then turns down -- way down -- our calorie burning rate. In the first 60 seconds of sitting, we start to burn only one calorie per minute. Sit for three hours at your desk at work? You just burned 3 calories. Were you eating a snack at your desk, drinking soda or coffee with cream in it? Then you certainly gained calories while sitting.

Sitting, for 2 Hours

Our good cholesterol, HDL, drops by 20%. We need a high HDL because it has proven to protect our blood vessels from the damage that leads to heart disease and acute cardiac events like heart attack and stroke.

Sitting, as a Daily Routine

Now consider the 80% of the U.S. population that sits most of their day at a desk job. Sitting for hours on a regular basis has shown to reduce insulin effectiveness by 24%, which leads to types 2 diabetes, sometimes referred to as "adult-onset" diabetes.

When we sit, we hold the muscles in our torso, shoulders, and neck in a relatively stable position. This causes our blood vessels to constrict (squeeze) which slows circulation. Blood flow matters, because it carries nutrients like oxygen and others to the muscles. When this slows down, it causes us to tire. Have you ever noticed how tired you get just from sitting in front of your computer for a while? That's exactly why it's happening.

Furthermore, because circulation slows drastically in the legs, blood pools and can cause varicose veins. And because our bodies function as a system of connected parts, the pooling of fluid in our legs creates issues elsewhere. For example, fluid retained in the legs during the day moves to the neck at night when we climb into bed to sleep. This can lead to sleep apnea. An estimated 22 million Americans suffer from sleep apnea, and researchers believe 80% are undiagnosed. 

The stomach doesn't escape the damages of sitting disease either. Not only does excessive sitting lead to obesity, colon cancer risk climbs as well for desk-jockeys. Sitting zeroes in on colon cancer specifically because enzymes in the blood vessels of the small muscles responsible for burning fat shut down. This disrupts the body's process for metabolism. Fuels that would be burned and used for energy or processed as waste from the body instead remain in the colon, creating an unhealthy environment that can lead to colon cancer.

But I Have to Work for a Living. How Do I Avoid Sitting So Much?

Well, do anything but sitting. Your other choices are standing and walking. Do those two things in the office as much as you can. 

One challenge with walking as much as you ought to is reduced productivity. If you need to be at your desk in order to get your work done, your boss is not going to be excited about you leaving your desk every thirty minutes so that you can take a brisk 15-minute walk.

The other option that can help you burn calories, keep your metabolism working properly, maintain a healthy flow of blood and electrical activity to all of your muscles, and keep your HDL cholesterol and insulin levels in good order, is to stand while you're working.

Simply standing while you read and write e-mails, talk on the phone, review and create spreadsheets and slide decks will help. You'd be surprised how many muscles are in action in our bodies just to make it stand in place. And forget what your elementary school teacher told you. It's good to fidget. Stretch. Shuffle your feet. Fidget away. It matters and helps.

Ask your boss if you can have a height-adjustable desk. Some are expensive, pricing out at over $1,500. But there are companies that will sell you just a base that they'll install under a worksurface in your cubicle or at your desk. The legs replace the cubicle hardware, and for far less than $1,000, you've got an electric height, push-button desk that you can raise and lower throughout the day.

You don't want to stand all day either. That can cause muskuloskeletal problems due to the weight and stress on the joints. But occupational therapists and ergonomists will tell you that you do need to vary sitting with standing throughout your day, every day. 

Which brings us full-circle to the original premise. Sitting too much will kill us, and in the worst possible way: slowly, gradually, and silently. To fight sitting disease, we need to take action today, as in now. I hope you were standing up while you read this.