Genes may have a strong influence over whether kids develop an eating disorder marked by extremely limited food choices, a new study finds.
The study focused on a condition called avoidant restrictive food intake disorder (ARFID). It's a relatively new diagnosis that describes people who severely limit the types or quantity of food they eat — but not over body image concerns or a quest for thinness.
Instead, food is the center of the issue. People with ARFID may have a strong aversion to various tastes, smells or textures, have little appetite, or may fear choking, vomiting or suffering an allergic reaction if they eat an unfamiliar food (often based on a past experience).
Studies suggest it affects 1% to 5% of the population.
Yet researchers still know little about the causes. The new study suggests genetic vulnerability plays a major role.
Looking at data on nearly 17,000 pairs of twins, Swedish researchers found that genes seemed to explain 79% of the risk of having ARFID.
"This strongly suggests that genetic studies have huge potential to help us understand the biological pathways underlying ARFID," said lead researcher Lisa Dinkler of the Karolinska Institute's Center for Eating Disorders Innovation in Stockholm.
An eating disorders specialist not involved in the study agreed.
The findings help affirm that there are biological processes underlying ARFID, said Kamryn Eddy, co-director of the Eating Disorders Clinical and Research Program at Massachusetts General Hospital, in Boston.
ARFID is not simply "picky eating," she said, or a matter of personal choice.
Research into the genetic component of ARFID could aid in understanding its root causes, which in turn could help refine treatment, according to Eddy, a member of the National Eating Disorder Association's Research Advisory Council.
It's not surprising that ARFID showed a strong genetic component.
"We do know that genetic factors contribute significantly to the development of other eating disorders," Dinkler said.
However, she noted, the "heritability" found in this study was greater than what has been seen with disorders like anorexia and bulimia. Heritability refers to the degree that genetic factors explain the risk of developing a health condition.
The findings, published online Feb. 1 in JAMA Psychiatry, are based on just under 17,000 twin pairs between the ages of 6 and 12. Some were identical twins, some were fraternal.
Identical twins share all of their genes, while fraternal twins are like non-twin siblings — sharing roughly half of their genes. So twin studies allow researchers to estimate the degree to which genes, shared environment or non-shared environment may contribute to a given health condition.
Overall, Dinkler's team found, 2% of kids in the study had an ARFID "phenotype" — meaning they had signs and symptoms of the disorder, based on parents' reports and medical and prescription drug records.
As part of the analysis, the researchers accounted for medical conditions that can affect appetite and eating, as well as autism, which can make kids highly selective eaters.
In the end, the investigators found that genes explained about 79% of the risk of having ARFID.
In general, young children are notoriously picky eaters. However, most grow out of that. Kids with ARFID go in the opposite direction, Eddy said, becoming more rigid in their eating habits as they grow older.
That can lead to nutritional deficiencies and stunted growth, although people with ARFID are not necessarily underweight. When ARFID persists into adulthood, it can also have social costs, as a workplace lunch or a dinner date could be impossible.
But people with the disorder can get help.
At Mass General, Eddy said, treatment for ARFID involves time-limited cognitive behavioral therapy, where people practice getting comfortable with a wider range of foods.
And while adults with ARFID may have spent many years with their eating habits, it's not too late to change them.
"We do know that ARFID is treatable," Eddy said, "and that's true for adults, too."
As for future research, Dinkler said her team wants to see whether ARFID shares any specific genetic factors with other conditions — including anxiety, neurodevelopmental disorders like autism, and gastrointestinal or metabolic illnesses.
The National Eating Disorders Association has more on ARFID.
SOURCES: Lisa Dinkler, PhD, postdoctoral researcher, Center for Eating Disorders Innovation, Karolinska Institute, Stockholm Sweden; Kamryn Eddy, PhD, co-director, Eating Disorders Clinical and Research Program, Massachusetts General Hospital, associate professor, psychiatry, Harvard Medical School, Boston; JAMA Psychiatry, Feb. 1, 2023, online