Eating disorders are serious mental illnesses characterised by an unhealthy preoccupation with eating, exercise and body weight or shape. Eating disorders can lead to physical, emotional and social consequences. Eating disorders have the highest mortality (death) rate of all psychiatric illnesses. Eating disorders are thought to affect up to nine per cent of the population, affecting both males and females and people from all cultural backgrounds. It is not known why someone gets an eating disorder. There is no single cause, but many factors may contribute such as genes and the environment that the young person grows up in.