Anorexia nervosa: could microbiota imbalance be hindering recovery?
According to a new study, the brain of individuals with anorexia nervosa may be under the influence of the gut microbiota. This discovery could pave the way for new treatment approaches centered on the gut–brain axis and its effects on mental health.
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About this article
Food restriction, intense fear of gaining weight, calorie obsession, body dysmorphia, bulimia, anxiety, depression, etc. Anorexia nervosa is a serious eating disorder that significantly affects a patient's health, impacting both behavior and the body. It is also particularly difficult to manage (read inset).
People affected by the condition often experience impaired cognitive function, particularly in certain learning abilities essential for behavioral adaptation, which may slow recovery.
A new study suggests the disorder could be linked to changes taking place in the gut microbiota. 4
4% of women and 0.3% of men Will be affected by anorexia at some point in their lives. ⁵
Between 14 and 17 years old Is the typical age of onset for anorexia nervosa (with a peak at 16). ⁶
A less diverse microbiota
The authors, researchers from the University of Graz in Austria, enrolled 15 patients with anorexia nervosa and 13 healthy female controls. All participants underwent tests to assess their implicit learning ability (see inset). At the same time, their stools were analyzed to determine the composition of their gut microbiota.
The researchers’ findings confirm that patients with anorexia nervosa show lower implicit learning scores than healthy volunteers. What is more interesting, however, is that these scores are linked to microbiota composition: the higher the scores, the more diverse the microorganisms.
When the gut microbiota scrambles the brain
How can this finding be explained? It’s well known that the gut microbiota influences brain function via the gut–brain axis. For example, it can alter stress responses or produce brain messengers (dopamine, serotonin, etc.) that can affect learning abilities.
In this study:
A high learning score was, for instance, linked to an increase in Bifidobacteria, bacteria that are key to gut–brain communication.These bacteria can help reduce anxiety and in turn influence learning processes.
1.5 to 3 years This is the average duration of an anorexia nervosa episode. ⁶
20% Some individuals remain anorexic for life. ⁶
Conversely, a low score was associated with an increase in Lachnospiraceae, bacteria that have been linked in several studies to depressive disorders that may impair brain function and implicit learning. These effects suggest a strong connection between the microbiota, behavior and mental health in conditions such as anorexia.
What is implicit learning?
Implicit learning occurs without conscious awareness or intention to learn 7. It doesn’t require memorization or focusing on rules. Leaning your body in the direction of a turn while cycling, for example, is the result of implicit learning. It differs from explicit learning, which involves acquiring theoretical knowledge, rules or principles.
Toward a probiotic-based treatment for anorexia?
This discovery is particularly intriguing as it may help explain why psychotherapy which partly relies on implicit learning is not always effective in treating anorexia. If confirmed, it could one day be possible to use probiotics containing Bifidobacteria to improve the management of anorexia nervosa. By stabilizing the gut–brain axis, these probiotics could help women return to normal eating habits.
Anorexia: the gut microbiota pathway?
1. https://www.ameli.fr/assure/sante/themes/anorexie-mentale/definition-frequence-causes#
2. https://www.camh.ca/fr/info-sante/index-sur-la-sante-mentale-et-la-dependance/troubles-des-conduites-alimentaires#
3. https://www.frm.org/fr/maladies/recherches-maladies-neurologiques/troubles-des-conduites-alimentaires/focus-troubles-conduite-alimentaires
4. Kipper JA, Wiener M, Horvath A, et al. Beyond the surface: gut microbiome and implicit learning in anorexia nervosa - A pilot study. J Psychosom Res. 2025 Jul;194:112164.
5. van Eeden AE, van Hoeken D, Hoek HW. Incidence, prevalence and mortality of anorexia nervosa and bulimia nervosa. Curr Opin Psychiatry. 2021 Nov 1;34(6):515-524.
6. Inserm
7. Université Bourgogne Franche-Comté
