A new brain imaging study shows what anorexia does to a person's brain, and how weight gain appears to reverse the changes

• MRI scans from a recent study show how anorexia can have a "drastic" impact on the brain.
• Women with anorexia had thinner cortical thickness, which is linked to lower intelligence.

A brain-imaging study on young women with anorexia found the eating disorder wears down key areas of the brain.

Researchers from various institutions in the Enigma Eating Disorders research group analyzed MRI brain scans of 685 women with anorexia and 963 healthy weight women from 22 places across the world. The women were aged between 15 and 27, with an average of 21. Most had been dealing with anorexia for about five years.

They then used those MRI scans to model the differences between the brains of healthy weight women compared to women with anorexia, and those in recovery from anorexia, as you can see in the image below.

According to the authors of the study, there were "drastic" differences in brain structure associated with general intelligence, with "significant" reductions seen in women with anorexia. The study authors said those changes were the greatest they had seen from any psychiatric disorder investigated by their group to date, including schizophrenia, depression, and OCD.

However, gaining weight appears to reverse the changes, the authors said. Previous research suggests this could happen within three months.

Underweight women had reduced cortical thickness, which is linked to lower intelligence

Women in the anorexia group had a body mass index (BMI) under 17.5 (15.4 was the average), and the control group of "healthy" weight women had a BMI above that threshold, with an average of 21.6.

Within the anorexia group, researchers also compared between the "acutely underweight" participants (described as "patients at the very beginning of weight restoration treatment") and those who were in treatment or moving towards a healthy weight.

In the brains of the participants with anorexia, researchers found "sizable" reductions in cortical thickness, subcortical volumes, and, to a lesser extent, cortical surface area. That translates to lower general intelligence, according to the researchers and previous studies.

Cortical reductions were greatest in those with the lowest BMIs and were less pronounced in those who were in recovery and had gained some weight, which, the researchers wrote in the study, highlights the effects of undernutrition.

Undernutrition leads to a shrinkage of the brain, lead study author Esther Walton, from the University of Bath, UK, told Insider.

"This shrinkage could indicate how 'healthy' brain cells or the connections between these brain cells are," Walton, an assistant professor in the department of psychology, said. "The reversibility of these effects, however, indicate that undernutrition does not immediately lead to cell death, which would be more permanent."

Weight gain can reverse brain changes, research suggests

Weight gain can reverse the brain changes, previous research, such as this 2021 meta-analysis, suggests.

For those who don't regain weight, how long the damage lasts is unclear and requires more in-depth study, Walton said.

The anorexia researchers underlined the importance of treatment for anorexia patients to prevent long-lasting structural brain changes.

"The drastic impact on the brain is strongly related to undernutrition and therefore rapidly changes with weight gain or treatment," researchers wrote.