Anorexia nervosa (AN) is a devastating eating disorder in which a patient severely restricts food intake and may have purging behaviors. AN of course results in physical harm but there are also very significant psychosocial effects because of the disease. Studies have shown that the gut microbiome plays an important role in weight gain and it is therefore reasonable to believe that gut dysbiosis could be seen in individuals with anorexia nervosa.
Scientists in Japan characterized the microbiome of AN patients and compared them to healthy controls. They studied 25 women with AN and compared their microbiomes to 21 age-matched healthy females. They found that AN patients had a lower amount of total bacteria and specifically, lower amounts of C. coccoides group, C. leptum subgroup, B. fragilis, and Streptococcus.
Several papers have shown the importance of gut bacteria on weight gain including those showing the impact that antibiotic use in poultry has on creating larger chickens. Other studies include those linking obesity to specific gut bacteria as well as studies that show transplantation of bacteria, specifically Christensenella minuta, reduced weight gain in mice.
These studies comprehensively show that there is some connection between gut bacteria and weight gain and therefore investigating it as a therapeutic mode for anorexia nervosa is logical. While this study was small in scale and no causal links can be made, it is important to understand that gut bacteria differs between AN patients and healthy controls. Microbiome therapies may be an option for treating anorexia nervosa.