Increasing rates of highly malignant hepatocellular carcinoma (HCC) and biliary tract cancers (GBTC) observed in Western populations may be related to obesogenic lifestyle factors and their metabolic consequences, such as metabolic syndrome (MetS), inflammation and altered production of bile acids (BA). Such lifestyle behaviours may induce changes in the gut microflora which in turn affect BA profiles, increasing their carcinogenicity. Some elevated BA may be oncogenic in exposed liver, bile ducts and gall bladder. Vertical sleeve gastrectomy may change bile acid composition.