Anorexia is a devastating eating disorder that can prove life-threatening.

Plagued by their illness, sufferers starve themselves causing excessive and often rapid weight loss.

Traditionally, a key symptom of the disorder is an intense fear of gaining weight.

But, a new study challenges this view, suggesting rather that anorexia is driven by the pleasure of losing weight.

The findings also add weight to the theory that the condition may be genetically influenced.

Professor Philip Gorwood, head of the Clinic for Mental and Brain Diseases at the Sainte Anne Hospital in Paris, said his team's research challenges the notion of fear of weight gain in anorexia patients.

Traditionally, a key symptom of anorexia is an intense fear of gaining weight. But, a new study challenges this view, suggesting rather that anorexia is driven by the pleasure of losing weight (file image)

Often associated with major psychological distress, anorexia nervosa is a condition that typically affects girls and young women, though boys and young men are affected.

Diagnosis is based on three international criteria - restriction of food intake resulting in weight loss, a distorted perception of weight and body and an intense fear of becoming fat.

Although there is no pharmacological treatment, Professor Gorwood's team, working with colleagues from Inserm and Paris Descartes University, focused on these clinical criteria.

Professor Gorwood said: 'When research is going nowhere, it is important to call into question the criteria at the very root of the disorder.

'We have therefore re-evaluated the last criterion, although it is quite prominent in patient discourse, by assuming that it is a mirror image of what is really involved, i.e. a reward for losing weight.

'We established the postulate that patients felt pleasure at becoming thin rather than fear of becoming fat.'

The findings suggest sufferers are driven by their pleasure at losing weight rather than a fear of gaining weight and becoming fat (file image)

So as not to be influenced by patient's discourse and analysis of their eating disorders, the researchers used a 'skin conductance test', which measures a person's sweating rate when they are exposed to various images.

The emotion caused by certain images actually leads to a rapid and automatic increase in sweating.

The researchers showed images of people of normal weight, as well as people who were overweight.

The photos were shown to 70 female patients at Sainte Anne Hospital.

For these patients, of varying weight and with different degrees of disease severity, viewing these images caused much the same reaction as in healthy subjects.

However, when they were shown images of thin bodies, the patients showed positively evaluated emotions, whereas healthy subjects had no particular reaction.

Furthermore, the researchers also investigated the heritable nature of the disorder.

One of the genes most often associated with anorexia nervosa codes for BDNF, a factor involved in neuron survival and neuroplasticity.

In patients with anorexia nervosa, the study indicates that the increase in sweating experienced when viewing images of thin bodies is explained by the presence of a specific form (allele) of the gene in question.

This result was confirmed after examining potential confounding variables such as weight, type of anorexia or duration of the disorder.

Professor Gorwood and his team conclude that future research should be geared towards reward systems rather than phobic avoidance.

And they suggest that certain therapeutic approaches, such as cognitive remediation and mindfullness therapy, may have clear beneficial effects on patients suffering anorexia.