With girls as young as seven suffering anorexia, we ask the experts why children develop eating disorders, the health problems such poor nutrition can cause, and whether the media and fashion industries are to blame.

With the current concern about obesity in children, the fact that some youngsters have quite the opposite problem seems to have been overlooked.

But outrage over the poor example set by stick-thin models has brought the issue of weight loss to the fore, and a top child psychiatrist has warned that some children as young as seven are now suffering from anorexia.

Dr Jon Goldin, a consultant child and adolescent psychiatrist at Great Ormond Street Hospital, which has a specialist centre for young children with eating disorders, warns: "A relatively small number of children as young as seven or eight develop eating disorders.

"Images in the media, which promote an ideal of thinness and glamorise excessive thinness may affect some individuals more than others, and in some may contribute to the development of an eating disorder."

However, Goldin stresses that there is no single cause of eating disorders, adding: "These are complex disorders with multiple factors contributing to their development."

These factors are likely to be a combination of events, feelings or pressures which lead to young people feeling unable to cope, from relationship problems and bereavements, to sexual or emotional abuse and even puberty.

It's also thought that genetics could play a small part in eating disorders, as could the attitude of other family members towards food.

Another major cause of eating disorders in children is bullying, says Steve Bloomfield of the Eating Disorders Association.

"Bullying is one of the key issues. Quite often the children are larger, and are bullied about it and finally decide to do something about it.

"But recent research has found that half of children bullied for being overweight are actually a normal weight for their age - it's just that the bullies perceive them to be overweight."

The peak age for the onset of eating disorders is between 15 and 25, with the majority of sufferers likely to be young females. However, 10% of cases are in males.

In anorexia nervosa, which is the main eating disorder that children develop, sufferers usually restrict the amount they eat, and may exercise to burn off perceived excess calories.

As well as poor or inadequate weight gain in relation to children's growth, or substantial weight loss, physical symptoms can include constipation and abdominal pains, feeling faint, and loss of periods.

Psychological signs may include an obsessive interest in what others are eating, and a distorted perception of body shape or weight.

In addition, there may be obsessive behaviour attached to eating, such as cutting food into tiny pieces.

Eating disorders in children can lead to growth restriction, fertility problems and osteoporosis.

"Parents need to be alert to the potential for problems, and watch what their child eats," Bloomfield warns.

"And they should remember that one of the characteristics of an eating disorder is that sufferers will try to hide it.

"As a parent you can't beat yourself up for not spotting something your child is trying to hide from you."