Exercise is good for health. According to the World Health Organisation (2013), adults should participate in 2 hours of moderate exercise each week. This will reduce the risk of diseases such as cancer and diabetes. Further evidence concerning the benefits of regular exercise was reported by the Smith in 2015: "2.5 hours of moderate exercise each week can reduce the risk of a heart attack by 47%". This shows that there is general agreement that to maintain good health, a few hours of moderate exercise is needed every week..