New research shows that office workers and other people who sit down a lot must exercise for one hour a day. If they do this, they will increase their chances of living longer. Doctors have been telling us for a long time that sitting down all day will shorten our life. Researchers now say that sitting in a chair all day is as dangerous to our health as smoking or being overweight. Research on over one million adults found that sitting for at least eight hours a day could increase the risk of dying early by up to 60 per cent. However, there is good news for those who sit at a desk all day. An hour's "brisk exercise" each day can cancel out the risk of an early death linked to sitting all day.