Anorexia and binge eating: Genetic study reveals eating disorders go beyond body weight

Eating disorders are widely considered to primarily be a mental health condition tied to weight and body image, but a new study suggests the picture is far more complex.

The research, by the Karolinska Institutet in Sweden, looked at genetic factors that could play a role in binge eating behaviours and anorexia nervosa.

Eating disorders affect millions of people worldwide, primarily in high-income countries, with Western Europe consistently showing the highest burden.

They involve abnormal eating and preoccupation with food, as well as prominent body weight and shape concerns. Symptoms result in significant risk or damage to health, distress or the impairment of normal functioning, and it is estimated that 95% of first-time cases occur by the age of 25.

The study, published in the journal Nature Mental Health, included nearly 40,000 individuals with binge-eating behavior and around 25,000 individuals with anorexia nervosa who were compared with more than 1.2 million individuals without eating disorders.

Researchers identified genetic variations that are statistically associated with a higher risk of developing an eating disorder like binge-eating behavior or anorexia nervosa.

“Our findings show that eating disorders are not just about body weight. Many of the genetic variants associated with these conditions differ from the variants that influence how much a person weighs,” said Lu Yi, principal researcher at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet.

“This provides a more nuanced picture for the biological basis of eating disorders,” she added.

Researchers found six genetic markers linked to binge eating and eight linked to anorexia, two of which — associated with anorexia nervosa — had not been identified before.

Scientists can then use these markers to calculate a "polygenic risk score," which sums up all the small effects of the markers a person carries. Someone with a high score has a larger collection of these risk markers and is statistically more likely to develop the disorders.

A biological link to other conditions

The study also found that carrying certain markers can indicate a shared biological vulnerability to other traits. For example, some markers for binge-eating are also markers for impulse-control behaviors, like smoking or risk-taking, higher body mass index (BMI) and attention-deficit hyperactivity disorder (ADHD).

Markers for anorexia, on the other hand, showed stronger genetic links to obsessive-compulsive disorder (OCD).

They also found that the genetic associations with binge eating and anorexia nervosa differ from the genetic factors that influence body mass index (BMI), even though body weight is an important factor in both conditions.

This suggests that eating disorders cannot be understood solely in terms of weight or metabolism, the authors noted.

“The study demonstrates that different eating disorders are partly driven by distinct biological mechanisms,” said Lisa Dinkler, assistant professor at Karolinska Institutet.

“In the long term, this knowledge may contribute to more targeted treatment strategies that take into account the specific characteristics of each condition.”

The researchers warned that these markers are still weak predictors of an individual’s status and must be combined with other risk factors to accurately understand a person's risk profile.