Most people think smoking is the worst thing they can possibly do for their health. But in reality, perhaps the worst thing of all is something most of us do every day: sit. We sit when we drive, work, eat, use the computer, watch TV and read. In fact, before you read any further, you should probably stand up. It turns out that the more time you stay planted on your rear, the less time you’re destined to live on this planet.

Here’s what we know:

Eye-opening research shows that keeping your butt in a chair (or on the couch) for hours at a time can lead to cancer, obesity, type 2 diabetes, cardiovascular disease and premature death. One study by the American Cancer Society found that women who sat six hours a day were 37 percent more likely to die by the end of the 13-year study period; men who sat were 18 percent more likely to die. Another study tied 49,000 U.S. cases of breast cancer and 43,000 of colon cancer to prolonged sitting.

Sitting isn’t dangerous just because it means you’re not exercising. It’s dangerous all by itself.

Prolonged time spent on your bum has significant metabolic consequences. It negatively affects your blood sugar, triglycerides, good cholesterol, resting blood pressure and levels of the “appetite hormone” leptin, all of which are biomarkers of obesity and cardiovascular disease.

Sitting also sabotages the lymph system, which helps the body fend off infections. Lymph vessels, which drain waste materials created by an infection, don’t have a pump like the heart; they’re controlled by rhythmic contractions of the muscles in your legs. So when you sit, the lymph system can’t do its job.

If you sit all day but make sure to get to the gym or go for a walk after work, isn’t that enough?

Unfortunately, no.

“Bursts of exercise is not the answer; 2 hours of exercise per day will not compensate for 22 hours of sitting,” . In fact, sitting for five or six hours a day, even if you spend an hour a day at the gym, is the equivalent of smoking an entire pack of cigarettes.

Moving more is tough, especially since most people’s jobs revolve around sitting. But breaking up endless time on your bum, even for a few minutes, can make a huge difference. Key enzymes move, blood flows, mind and muscles flex. Here is what you can do to sit less:

1. Get up and move at least every 30 minutes. Make an effort to go get water or coffee so you’re forced to stand. Pace up and down the hall or just stand when you’re on a phone call. Even fidgeting helps.
2. Go ahead, watch your favorite TV shows—but don’t just sit there. Cook, fold laundry, empty the dishwasher or ride a stationary bike.
3. If you have to spend all day at your computer, consider investing in a treadmill desk . That way you can keep moving even while you work.
4. Make sure you exercise. Even though working out won’t completely rid you of the negative effects of sitting, a study found that active people who sat for long periods of time lived longer than inactive people who sat. Try a morning or lunchtime workout to get yourself going or make a mini-workout of your household chore

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