Anorexia nervosa is a common eating disorder that often starts with normal dieting to lose weight, but turns into a form of intentional starvation, causing a person to become dangerously underweight.
People with anorexia nervosa become obsessed with dieting and weight. They develop a fear of becoming fat and have a distorted image of their body, seeing themselves as fat, even when they're very thin.
Under-eating, vigorous exercise, ritualistic food habits and abuse of laxatives cause excessive loss of weight.
Most anorexic people have no history of being overweight.
Anorexia nervosa usually starts in the mid-teens, although it can start at a younger or older age. Women are more likely than men to have anorexia - about 90 per cent of those affected are female.
It's estimated about three or four people in every 100 have anorexia. Most deny they have a problem and many have depression. It can run in families.
It's difficult to prevent anorexia from developing because it's unclear precisely why the condition occurs. But it may be possible to avoid or address some risk factors, such as social and cultural pressures to be thin, bullying, low self-esteem and family dysfunction. The most important step is recognition by the individual that they've got a problem.
After assessment by a psychiatrist at a specialist eating disorders unit, counselling, antidepressants and advice on healthy eating may be offered.
Admission to hospital is often needed to treat any physical problems that have resulted from under-eating.