A 15-minute workout at the gym helps keep you young as well as fit, according to a study. Researchers found that brief vigorous exercise tends to slow the ageing process. Just 15 minutes of energetic activity a day reduces stress and prevents the deterioration of vital cells which lead to us feeling and looking older, reports express.co.uk. Even if we are stressed, which tends to speed up the ageing process, we can hold time at bay by working up a sweat. Psychologist Eli Puterman, who led the groundbreaking research, said the study is built on previous work that showed how changes in DNA result in ageing. "We have extended those findings to show that, in fact, there are things we can do about it," said Puterman. "If we maintain the levels of physical activity recommended by public health bodies we can prevent the damage that psychological stress may have on our body," he added.