More than 500 New Zealanders who posted off a tube of saliva have helped produce the largest genetic study of eating disorders yet attempted, and the result sharpens a long running argument about what these illnesses actually are.
The work was published on 19 August in the journal Nature Mental Health. It was led by the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, working with an international partnership that included a University of Otago team based in Christchurch. It is the first time researchers have compared the DNA of people who binge eat with the DNA of people who have no eating disorder at all, and it also contains the biggest genetic study of anorexia nervosa yet run. The paper can be read on the Nature Mental Health website.
The scale is what makes it unusual. The researchers pulled together 27 datasets from around the world, covering almost 40,000 people who binge eat and more than 1.2 million people who do not. They then compared the DNA of about 25,000 people with anorexia nervosa against the same comparison group.
Out of that came six spots in the genome linked to binge eating and eight linked to anorexia nervosa among people of European descent. Six of the eight anorexia sites had already turned up in a 2019 study, which strengthens the case that they matter. Two of them had never been identified before.
The finding the researchers keep returning to is that none of this maps neatly onto body weight. Both conditions are bound up with weight in the clinic, yet the gene variants involved are largely not the ones that govern how heavy a person is.
Helena Davies, a postdoctoral research fellow at the institute and a joint first author, said in the King’s College London release that the study “confirms on a genetic level that eating disorders are not just about body weight; many of the versions of genes linked to these conditions are different from the versions of genes that are linked to how much someone weighs”.
Where weight biology does show up, it points in opposite directions for the two conditions. RNZ reported that gene variants associated with a higher body weight made binge eating more likely, while the same variants made anorexia nervosa less likely. That is the sort of pattern that only becomes visible at this sample size.
Some of the binge eating sites sit near a gene called FTO, which has been studied for years because of its link to higher body weight. The researchers suggest binge eating may explain part of that link, which would be a small but useful correction to a well worn piece of obesity science.
The New Zealand contribution runs through the Eating Disorders Genetics Initiative, the local arm of which is led at the University of Otago’s Christchurch campus by Professor Martin Kennedy and Associate Professor Jenny Jordan. Volunteers here filled in an online questionnaire and sent back a saliva sample for genotyping, and their data went into the international pool alongside participants from the United States, Australia and Denmark. RNZ reported that more than 500 New Zealanders were part of this study.
Jordan told RNZ Morning Report the findings should feed into how these conditions are treated. “These results not only help us understand both shared and distinct causes of these eating-related traits but may also help us develop more precise treatments targeting the specific biology of each condition,” she said.
The next phase of the project will draw on roughly 4,000 New Zealand participants, close to eight times the number who fed into this paper.
Jonathan Coleman, a senior lecturer in statistical genetics at King’s and the lead senior author, said the value of the work is that it widens the field beyond one diagnosis. “We’ve been making important progress in understanding the genetics of anorexia nervosa for several years, but that’s only one of several eating disorders that have major impacts on people’s lives,” he said. “This work is really important – we go beyond anorexia nervosa and start to understand the genetics of binge eating, which affects many people with eating disorders. We’re hopeful that our findings will allow future research to improve the lives of people with all eating disorders.”
There is a real limit on the findings, and the researchers state it plainly. The genetic signals were identified in people of European ancestry. That is a common shortcoming in this field, and it matters more in New Zealand than in most places, because a result drawn from European genomes cannot be assumed to hold for MΔori, Pacific or Asian New Zealanders without being tested. The team says it now plans to extend the analysis to global ancestries and to other conditions, including avoidant and restrictive food intake disorder, which involves severe limits on what a person will eat without the body image element seen in anorexia.
The study came out of the Eating Disorders Working Group of the Psychiatric Genomics Consortium and was funded in part by the United States National Institutes of Health, with further support from the National Institute for Health and Care Research Biomedical Research Centre at the Maudsley.
None of this changes treatment tomorrow. Genetics does not settle who gets an eating disorder and who does not, and the therapies that work now still rest on nutrition, psychological treatment and family support. What a result like this can do is shift the conversation. Families have spent decades being told, sometimes gently and sometimes not, that an eating disorder was a matter of willpower, vanity or parenting. A list of gene sites does not cure anyone, but it does put the illness in the same category as other conditions with a measurable biological footprint.
Services here have been under pressure for years. In April the Government began rolling out peer support workers into specialist eating disorder services around the country, backed by an extra $4 million a year and a refreshed national strategy, the first update in 16 years. Mental Health Minister Matt Doocey said at the time the aim was “reducing wait times and improving access to eating disorder support”, with more than $3.2 million over four years set aside for the peer roles. RNZ covered the rollout at the time.
Anyone worried about their own eating or someone else’s can start with a GP, or contact the Eating Disorders Association of New Zealand, which keeps a list of specialist services by region.
Does knowing there is a genetic component change how you think about eating disorders, or does it risk letting the rest of the picture off the hook? Tell us in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job π
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