Scientists have discovered some people have a genetic predisposition to anorexia – offering hopes of better treatments for the often tragic eating disorder.
Nearly 2 per cent of Kiwis will suffer from an eating disorder in their lifetime – and a third of those will have anorexia, according to Anorexia New Zealand.
People suffering from it cut down on their food intake drastically, which causes dramatic weight loss, and most had a distorted view of their body and an intense fear of gaining weight.
Worse still, the nature of anorexia, which had the highest mortality rate of any psychiatric disorder, means sufferers could truly believe that they don't have a problem.
Breakthrough findings published today suggest that some people are genetically at risk of developing the disease, through a predisposition that affects how their brain and metabolic system function.
The international team behind the study, including New Zealand researchers, sampled the DNA of almost 17,000 patients and compared it with that of more than 55,000 people without anorexia around the world.
They found eight genetic variants significantly associated with anorexia nervosa, showing its origins appeared to be both metabolic and psychological.
The researchers also found these genetics overlapped with traits linked with people's ability to metabolise fats and sugars, and body mass index, and also influenced physical activity, which might explain the tendency for some sufferers to be highly active despite their low calorie intake.
Further, they found a genetic connection with other psychiatric disorders such as obsessive-compulsive disorder, depression, anxiety and schizophrenia.
There remained no specific medications for anorexia nervosa, and treatments were mainly psychological therapies that tried to help sufferers regain weight and re-establish normal eating.
Study co-author and Otago University researcher Dr Jenny Jordan said the findings gave a new way of looking at the disease.
"For example, many people diet but only a few develop anorexia nervosa with very low levels of weight and sometimes extreme levels of exercise," she said.
"The findings that there are genetic differences relating to metabolism in people with anorexia in our study helps make sense of that. It may also help explain in part why recovery is such a struggle.
"These findings, that it is not just a psychiatric condition, will be hugely validating for many with anorexia nervosa and their families."
Otago University's Professor Martin Kennedy said the findings indicated that some people are born with a genetic predisposition for developing the disease, but not all of them would.
"Our hope is these fundamental genetic insights will point to better ways of preventing the disorder, and better medications that target the underlying biology," he said.
"Nobody chooses to succumb to this awful disease, and we need these kinds of new insights to help people survive and move on with their lives."
The study has been published in major scientific journal Nature Genetics.
ANOREXIA: THE WARNING SIGNS
• Anorexia is one of the most common eating disorders in New Zealand. Sufferers will often use methods such as excessive exercise, purging, laxatives, enemas and diuretics to lose more weight.
• One of the most obvious symptoms is anxiety around food, with the person skipping meals, cutting out types of food, being secretive about eating, and severely restricting.
• The nature of the illness, combined with the effects of malnutrition often also cause personality changes, mood swings, and confrontational behaviour, particularly around food.
• People with the disorder often make a huge effort to disguise their eating and body changes, and commonly deny that anything is wrong.
- Source: Eating Disorders Association of New Zealand