No matter how much you exercise, sitting for long periods of time at work is really, really bad for your health. And can make you dumber.

But it turns out sitting at home is even worse.

First the work problem:  Sit for the majority of the day and your risk of cardiovascular disease doubles compared to people who stand. Sitting for more than six hours a day can make you 18% more likely to die from diabetes, heart disease, and obesity than people who sit less than three hours a day.

Sound horrible? It is. But not compared to what sitting on our couch can do to you. According to one new study, people who spent four or more hours sitting in front of the TV each night were nearly 50 percent more likely to have a heart attack than those who spent less than two hours watching TV each day.

Why such a dramatic difference? For one thing, sitting at work -- however "stuck" at your desk you might feel -- still tends to be a lot more active than sitting on your couch. You pop into a colleague's office. You head to the break room. You shift and fidget and stretch. After all, no matter how ergonomically designed... your office chair isn't that comfortable.

But your couch is. So you kick back. You sink in. And you bring a few snacks along for the ride -- because couch time is "me" time.

According to the researchers:

Even when you're sitting at your desk, you can be fidgeting or stretching which may not seem like much movement, but every little bit can help... which is better than prolonged, uninterrupted sedentary time, which can occur more with television watching, especially at night when you're tired. 

And Then There's This

The researchers also found that people who spent more time on their couches watching TV were more likely to be less active and were more likely to smoke, drink, and maintain a less healthy diet.

Contract that with people who sat the most at work; generally speaking, those folks were younger, exercised more, and ate healthier. (And they made more money.) 

(To be honest I'm not sure what to make of that result, other than that "knowledge work" tends to pay better than physical labor... and that people who work hard to improve one area of their life tend to work on other areas, too -- what I call the improvement ripple effect.)

Add it all up, if you sit for more than 11 hours a day (since that makes you 40% more likely to die in the next three years compared to people who sit for less than four hours), and for three to four hours a night on your couch...

Clearly, whoever invented sitting did not have our best interests at heart.

But Here's the Good News

The researchers also found this: Engaging in approximately 30 minutes of moderate to vigorous exercise each day can ward off the health risks of prolonged sitting. 

Think of "moderate" as exercise that elevates your heart rate and respiratory rate... but not to the degree that you can't carry on at least something of a conversation. (With the occasional gasp for breath mixed in.) 

And then try focus on breaking up your "seat time" as often as you can. When you're at work, stand and stretch every 30 minutes. Stand when you're on the phone. Take a walk at lunch. Do what LinkedIn CEO Jeff Weiner does, and hold walking meetings.

The same is true at home. If you watch an hour of TV, take a break before Netflix automatically cranks up the next episode. Get up.Get around. Do something.

Not only will you feel a little more productive at the end of the night... you'll also be a lot more likely to live longer.

Can't beat that.