The finding suggests that disruptions in the part of the brain handling food intake can contribute to various eating disorders.
Researchers have known for several years that a person's odds of developing the eating affliction depends partly on genetics, but this is the first time an actual gene has been identified as causing the disease.
Researchers from the Netherlands and Germany studied 145 anorexia patients and 244 without the disease. They found that 11 percent of those suffering from anorexia had a mutant form of the gene for agouti-related protein, a chemical that helps stimulate appetite. Only 4.5 percent of subjects without the illness had the variant form, leading to the conclusion that having the mutation more than doubled the chances of acquiring the illness.
The study's findings, published in the May issue of Molecular Psychiatry, suggests that a drug mimicking agouti-related protein may help some anorexics regain their desire to eat.
The effect of the genetic mutation is not yet known, but it is thought to cause a slight change in the shape of the agouti-related protein. The change could affect the protein's usefulness, and thus affect how the brain stimulates the desire to eat.
And while this particular gene appears to be involved with the disease, researchers believe other genes and environmental factors play a role in the disorder.
"It may contribute to explaining why a small proportion of people get eating disorders," said Walter Kaye, a psychiatrist at the University of Pittsburgh. "But it's not going to explain everybody."
It's estimated that around one percent of teen-age girls in the U.S. suffer from anorexia. The disease also occurs in boys, but not as frequently. Anorexia - literally "without appetite" - causes an obsession with body image. Sufferers anguish over dieting and calorie counting, seeing every bite of food as a threat. In extreme cases the disease can prove fatal, as in the case of the late singer, Karen Carpenter, who died of a heart attack brought on by anorexia.
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