The past few years have seen people sitting longer – sitting while at work, while driving, while watching TV or eating or while studying.  But studies have shown that prolonged sitting is bad for the health, even though a person exercises regularly.

A person who sits six or more hours a day will feel the negative effects in 10 to 20 years while one's lifespan will be shortened by as much as seven years. Researchers have claimed that sitting for extended periods of time should be considered a major threat to public health, one that's as serious as smoking.

Prolonged sitting raises the risks of fatal heart problems by 64 percent and the risk of prostate cancer or breast cancer by 30 percent. It also has a big impact on one's metabolism, making it difficult for the body to regulate blood sugar levels, blood pressure and cholesterol, thereby exponentially increasing the chances of one becoming obese.

The research is significant enough that different countries are recommending that people take "an active break from sitting every 30 minutes," even those who exercise regularly.

As Professor Stuart Biddle of Australia's Victoria University explains it, "if someone goes to the gym or walks for 30 to 45 minutes a day, but sits down the rest of the time, then they are still described as having a 'sedentary lifestyle.'"

Doctors currently advise people to exercise at least 150 minutes a week and to look for ways to reduce the time spent sitting or lying down. But while the research so far doesn't indicate how long a person should sit, there are certain things most doctors agree on. For instance:

Children under 5: Doctors recommend that parents should limit the time children spend watching TV, strapped in the buggy or travelling by car, bus or train. This is admittedly a challenge for parents in today's fast paced and busy lifestyles but a Stay Active report says that "sedentary behavior in the early years is associated with overweight and obesity."

Children 5 to 18 years: Research has shown that children in homes with multiple TVs and computers tend to sit for longer periods. There are several ways that parents can cut down on sitting time, like making bedrooms a TV and computer-free zone, setting a family limit to daily screen time, encouraging children to do household chores like taking the garbage out and choosing gifts that encourage active play (ball, skateboard etc.)

Adults: People 19 to 64 years old should find ways to minimize the time they spend sitting down. For instance, stand when taking the train or bus, take the stairs instead of the escalator, take a walk break every time one takes a coffee break or alternately stand and sit while working. Setting an alarm every 30 minutes is a good way to remind oneself to stand up, stretch and walk around.