Abstract Obesity is epidemic; chronic energy surplus is clearly important in obesity development but other factors are at play. Indigenous gut microbiota are implicated in the aetiopathogenesis of obesity and obesity-related disorders. Evidence from murine models initially suggested a role for the gut microbiota in weight regulation and the microbiota has been shown to contribute to the low grade inflammation that characterises obesity. The microbiota and its metabolites mediate some of the alterations of the microbiota–gut–brain axis, the endocannabinoid system, and bile acid metabolism, found in obesity-related disorders. Modulation of the gut microbiota is an attractive proposition for prevention or treatment of obesity, particularly as traditional measures have been sub-optimal