Anorexia nervosa and microbiota: systematic review and critical appraisal

PURPOSE: Recent studies have reported a gut microbiota imbalance or dysbiosis associated with anorexia nervosa (AN), which has prompted an appraisal of its aetiological role, and the reformulation of AN as a metabo-psychiatric disorder. Thus, the aim of this paper was to critically review the current scientific findings regarding the role of microbiota in anorexia nervosa. METHODS: A systematic study of peer-reviewed literature published in four databases between 2009 and 2022 was conducted according to PRISMA guidelines. Both human and animal studies were included. RESULTS: A total of 18 studies were included. In animal models, both the preclinical and clinical findings were inconsistent regarding microbiota composition, faecal metabolite concentrations, and the effects of human faecal microbiota transplants. CONCLUSION: The methodological limitations, lack of standardisation, and conceptual ambiguity hinder the analysis of microbiota as a key explanatory factor for AN. LEVEL OF EVIDENCE: Level I, systematic review. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40519-023-01529-4.