A study to identify the genetics associated with anorexia nervosa has the potential to "rewrite the book" on treating the potentially fatal disease, say researchers.
The researchers from the University of North Carolina (UNC) School of Medicine have collected blood samples for 15,000 people - including New Zealanders - for the very first study of the genetics involved in the disease.
They have already found the first genetic marker for anorexia nervosa, suggesting there may be metabolic factors behind the disease, such as cholesterol, insulin and glucose levels, which may need to be taken into account, in addition to psychiatric components, such as a perceived drive for thinness and weight preoccupation.
Anorexia affects an estimated 21,000 New Zealanders. While a quarter make a full recovery, the disorder carries risk of chronic ill-health and death.
UNC's Dr Cynthia Bulik - the study's senior author - said the researchers were asking people to completely forget everything they used to think about the disease, because most of it was wrong.
"What we've been looking at, in various different ways for the past decade and a half now, is the role that genes play.
"We have the potential here to be basically rewriting the book on anorexia nervosa."
Dr Bulik, who is a former clinician at Christchurch's Princess Margaret Hospital and researcher at the University of Canterbury, said the current research built on earlier studies that looked at why the disorder was often found to run in families. Those studies found 50 percent of the liability towards developing anorexia was due to genetic factors.
She said the new study went one step further, to look into the genes involved.
The researchers found the first genetic marker for anorexia nervosa on chromosome 12, in a region previously shown to be associated with type 1 diabetes and auto-immune disorders.
Dr Bulik said this meant there were potentially similar mechanisms that were underlying those illnesses.
She said unlocking the secrets behind the possible genetic contribution to anorexia could help treat victims whose bodies might pull them back down to dangerous weight levels, after they had been treated.
"It's sort of like metabolic bookends. With obesity, it's the same thing happening, but in the opposite direction."
Despite the promising results, Dr Bulik said the psychiatric basis for treating anorexia could not be abandoned.
"We still need to work on that level, because we don't have an intervention yet that can address these metabolic issues, so we still need to [be] using psychotherapy.
"Food is still the best treatment for anyone with anorexia nervosa to try and get their weight back up to a healthy level, and get their bodies to stay there."
If you're worried about the way you or a family member are eating, talk to your GP or health practitioner. For more information about anorexia and other eating disorders, and where else to go for support, visit the Ministry of Health's website.