10-12 week old male FXR KO mice and their WT littermates, described elsewhere 49 and bred from founders acquired from the Jackson Labs (Bar Harbour, ME), were singly housed in an AAALAC-approved facility with a 12-12 light-dark cycle, and allowed ad libitum access to HFD (D12492, Research Diets, New Brunswick, NJ) and water unless otherwise noted. After 10 weeks of HF-feeding, male mice were randomly divided into body weight and fat-matched groups within genotype, and we performed VSG or sham surgery as above. Based on our power analyses, completed using previous **data** to determine the expected variance and effect sizes, and based on our historical **data** regarding post-operative mortality, we performed sham surgery on 13 WT and 9 KO mice and VSG surgery on 14 WT and 15 KO mice. 5 KO-VSG and 4 WT-VSG mice died from complications of surgery and were not included in any of the analyses. Food intake and body weight was monitored weekly. Body composition was measured 1 week prior to and 11 weeks following surgery by magnetic resonance imaging (Echo Medical Systems, Houston, TX). An additional 1 WT-sham, 2 KO-VSG and 2 WT-VSG mice died (or were found moribund) during the period of metabolic phenotyping that occurred between weeks 8 and 15. For any given analysis, only mice that are represented throughout the entire timecourse were included. In addition, for the macronutrient preference study, **data** from several individuals were excluded based on pre-established criteria-in this case, that the mice consistently spilled the powdered macronutrient diets on the cage floor making accurate measurement of what was ingested impossible. For the microbiota analyses, one WT-VSG individual was excluded due to a noted investigator error while collecting the cecal samples at sacrifice.