Some children and adults develop an unusual eating disorder where they restrict the food they eat, but not because of body image issues or a desire to lose weight. Not much is known about what causes this particular disorder, but researchers say genetics may play a role.
People with avoidant restrictive food intake disorder tend to have little appetite and severely limit the types or quantity of food they eat due to a strong aversion to the smells, texture or taste of certain foods or from fear of choking, vomiting or having an allergic reaction.
Research has suggested that a past traumatic event involving food could be a risk factor. The eating disorder, which affects up to 5% of U.S. children, is often also found in people with autism and anxiety disorders. According to Neuropsychiatric Diseases and Treatment, an estimated 3.2% of the general population is diagnosed with avoidant restrictive food intake disorder, including 14% to 22.5% of children in pediatric treatment programs for any type of eating disorder.
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A new study of almost 17,000 pairs of twins conducted by Swedish researchers suggests there may be a genetic risk factor for this eating disorder. They calculated that genes may explain 79% of the risk of having avoidant restrictive food intake, while nonshared environmental factors accounted for 21% of a person's individual risk.
There have been very few genetic studies on this type of eating disorder. Lead researcher Lisa Dinkler of the Karolinska Institute's Center for Eating Disorders Innovation in Stockholm and colleagues says that their findings highlight the need for more genetic research, including looking for shared genetic risk factors with other medical conditions such as anxiety, neurodevelopmental disorders such as autism and gastrointestinal or metabolic illnesses.
Kamryn Eddy, co-director of the Eating Disorders Clinical and Research Program at Massachusetts General Hospital in Boston, told U.S. News & World Report that the findings help confirm that there are underlying biological factors involved; it is not a case of people simply being picky eaters. Eddy, a member of the National Eating Disorder Association's Research Advisory Council, was not involved in the research.
The study, published in JAMA Psychiatry, is based on genetic data from just under 17,000 pairs of twins between the ages of 6 and 12. Some of the pairs were identical, sharing all of their genes, and some were fraternal, which means just like all siblings, they share about half of their genes. Twin studies are often used to determine what percentage of genes contribute to a medical condition compared with environmental factors.
The researchers found that of all the study participants, 2% had signs and symptoms of the disorder based on reports from the parents and medical and prescription drug records. Children with other conditions that can affect appetite and eating and those with autism were not included in the analysis.
Previous studies have suggested that people with autism, a psychiatric disorder (especially an anxiety disorder) and those with intellectual disabilities are more likely to develop avoidant restrictive food intake disorder.
Dinkler told MedicalResearch.com that the genetic component of avoidant restrictive food intake disorder is higher than that of other eating disorders and similar to that of neurodevelopmental conditions such as autism and ADHD.
"Our results strongly suggest that twin studies and molecular genetic studies have huge potential to help us understand the biology underlying ARFID. Our finding is also important as the knowledge that mental disorders are strongly influenced by genetic factors can help reduce stigma and blame, which is a huge problem in the field of eating disorders," she explained.
Children and adults with avoidant restrictive food intake disorder often develop nutritional deficiencies and have trouble maintaining a healthy weight. In children, it also affects their growth and development. Signs and symptoms of this type of eating disorder include dramatic weight loss, dressing in layers to hide weight loss or to stay warm, frequently reporting constipation, abdominal pain, lethargy and in some cases excess energy. People suffering from it often have vague gastrointestinal complaints at mealtimes.
Because a person with this type of eating disorder does not consume enough calories to support the basic functions of the body, in extreme cases their bodies can shut down. People with an eating disorder are also more likely to experience imbalances in sodium, magnesium, potassium and calcium.
Common physical symptoms of avoidant restrictive food intake disorder include stomach cramps, menstrual irregularities in women, anemia, low thyroid and hormone levels, low potassium and a slow heart rate. Some individuals with this eating disorder may also experience fainting spells, dry skin, dry and brittle nails, thinning hair on head, muscle weakness, poor wound healing, impaired immune functioning and difficulties with concentration and sleeping.
The good news is that this condition is treatable. Cognitive behavioral therapy is often recommended to help the individual become more comfortable with a wider range of food, and start a more sustainable diet.