Anorexia nervosa: gut imbalance fuels eating disorders

Anorexia nervosa is an eating disorder that affects 1% of the population, with 95% of cases occurring in women. It is characterized by distortions of body image and obsessions with weight loss, leading to a drastic voluntary restriction of food intake.

This in turn leads to emaciation and health complications that can sometimes result in death. The causes of anorexia nervosa remain poorly understood, and its management is complicated, resulting in remission in less than half of cases. Previous studies involving a small number of patients had already associated a gut microbiota imbalance (dysbiosis) with the disorder. Does gut dysbiosis promote the development of the disease?

Profoundly disturbed gut microbiota in anorexic women

Researchers analyzed stool and blood samples taken from 77 women suffering from anorexia nervosa and 70 healthy women of the same age. They compared gut microbiota composition and blood metabolites (sidenote: Metabolites Small molecules produced during cellular or bacterial metabolism. For example, short-chain fatty acids are metabolites produced by intestinal microbiota during fermentation of non-digestible complex carbohydrates (fibers, etc.). Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020;11:25.  Lamichhane S, Sen P, Dickens AM, et al An overview of metabolomics data analysis: current tools and future perspectives. Comprehensive analytical chemistry. 2018 ; 82: 387-413 ) between the two groups, and indeed found differences. For example, the gut microbiota of the women suffering from anorexia nervosa contained fewer bacteria from the genus Roseburia, which are considered beneficial to health. In addition, the greater the abundance of bacteria from the genus Clostridium, the more severe the anorexic symptoms, suggesting that these species are involved in the regulation of eating behavior.

Gut microbiota contributes to eating disorders

The researchers then transplanted fecal samples from women suffering from anorexia nervosa to germ-free (sidenote: Germ-free mice mice that have no microbes at all, raised in sterile conditions. )  mice. After three weeks of a 30% reduction in food intake (to mimic the eating behaviors of anorexic patients), the mice given fecal samples from anorexia nervosa patients had lost more weight and took longer to return to normal weight than the “control” mice. A functional analysis of the bacteria present in the mice’s feces then confirmed the role of the gut microbiota in controlling eating behavior.