Some of the genetic factors linked to anorexia nervosa are also associated with metabolism, suggesting that there may be a biological explanation for why patients with the eating disorder lose weight so rapidly and struggle to keep weight on.
The new discovery was part of the largest genome-wide association study of the disease ever done. The study, published July 15 in the journal Nature Genetics, found eight genetic regions linked to anorexia.
Anorexia affects up to 4% of women and a smaller percentage of men. It is among the deadliest of psychiatric disorders. People with the disease have long battled stigmatization, getting labeled as having a vanity condition driven by a desire to be thin. But researchers call the study the most specific and definitive evidence that genes and biology play a prominent role. Though far off, researchers hope the discovery will help start the process of developing treatments that target the biology of the disease.
“Many of us have wondered for a long time if there is more to anorexia nervosa than the psychological component,” says Cynthia Bulik, founding director of the UNC Center of Excellence for Eating Disorders in Chapel Hill, N.C., who led the study. “These people just override normal biology, they override hunger signals. We’ve often wondered what it is that permits them to lose so much weight and stay down there. This might help explain why they get metabolically out of control.”
The study analyzed the genomes of nearly 17,000 patients with the disease and compared them with 55,525 controls from 17 countries. Still, its findings are preliminary and need to be replicated, researchers say.
Researchers also found people with the condition are genetically prone to high physical activity levels and more likely to have other conditions, including obsessive-compulsive disorder, depression, anxiety and schizophrenia.
Dr. Bulik says the goal is to collect 100,000 genetic samples. She expects researchers will find hundreds of genes associated with the disease.
Only about 30% of people with anorexia nervosa fully recover. The research underscores the importance of ensuring that patients get to a healthy weight to allow their metabolism to stabilize before they leave residential treatment programs. This could reduce the risk of relapse after they go home, Dr. Bulik says.
June Alexander, a 68-year-old writer in Melbourne, Australia, was among the nearly 17,000 people who contributed a blood sample for the study.
Ms. Alexander was diagnosed with anorexia in her 30s after struggling with the disease starting at age 11. She says she wasn’t successfully treated until she was 55. “That was when I was able to eat three meals every day and not feel guilty,” she says.
The study’s findings, she says, were a “big relief.”
“This illness makes you feel very ashamed,” Ms. Alexander says. “This study is saying this is definitely an illness. I’m not flawed. It’s the illness that makes me feel and seem that way.”
Tom Hildebrandt, chief of the Center of Excellence in Eating and Weight Disorders at Mount Sinai School of Medicine in New York, called the research the “first step in identifying a road map for the neurobiology of the illness.”
That about 20% of the illness could be derived from metabolic genes is hugely important in reducing the stigma associated with the disease, says Dr. Hildebrandt, who wasn’t involved with the study. “Anorexia is considered a self-control problem, just eat and it will solve the problem,” he says. “The reality is they’re working against their own physiology—it’s actually much harder for them to eat not just because of the psychiatric resistance to gaining weight but they’re also fighting a fundamental biology that doesn’t really want them to gain weight either.”
Dr. Hildebrandt says he sees this with his own patients who have difficulty gaining weight and keeping it on. “Part of the reason they get stuck is, from a psychiatric standpoint, they’re anxious about eating and the effects of eating. But in addition, they have to eat a lot more. They have to work harder to eat than the average person,” he says. It’s unclear if people are born with such metabolic genes or if such genes are activated by a state of starvation.
The study’s limitation, Dr. Hildebrandt says, is that it wasn’t an independent sample. It included samples from 17 separate studies without a uniform set of measurement standards.
Walter Kaye, a psychiatry professor and executive director of the Eating Disorders Program at the University of California, San Diego, contributed materials from earlier genetic studies to the current one.
Dr. Kaye says he’s noticed how hard it is for some of his patients to gain weight. Anorexia patients might need to consume 4,000 to 5,000 calories a day to do so. The average woman needs 2,000 calories a day to maintain her weight. “That’s an enormous amount of food,” he says.
He’s also published studies showing that after people recover from anorexia, they often need to eat significantly more than most people to maintain their weight. “We don’t know why these people are prone to get hypermetabolic, although it may not persist in the long term,” he says.
Laura Collins Lyster-Mensh, executive director of FEAST, a nonprofit advocacy group for the families of those with eating disorders, says the group helped recruit participants for the study and raised money to help fund it. “A lot of us parents see clearly that what’s happening to our kids is biological and metabolic in nature, but we haven’t had the proof,” says Ms. Lyster-Mensh, whose daughter suffered from anorexia in 2002 as a 14-year-old.
“The DNA research reinforces what the families of FEAST have been saying for a long time, which is: Help us feed our kids properly and stop blaming our loved ones for choosing a disorder of vanity,” Ms. Lyster-Mensh says. “They didn’t choose it.”
Write to Sumathi Reddy at firstname.lastname@example.org
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