Dietary Macronutrient Intake and the Gut Microbiome in Adults Undergoing Bariatric Surgery for Obesity.

Limited information linking dietary intake to gut metagenomic data in bariatric surgery patients is available. We examined whether there were correlations between macronutrient intake and the gut microbiome and related gene pathways prior to and following bariatric surgery. Participants were 29 adults living with obesity undergoing bariatric surgery (93% females). Three-day food records were analyzed prior to and after surgery to estimate mean daily intakes of macronutrients to derive measures of diet quality [glycemic index, added sugar intake, and the Healthy Eating Index 2015 (HEI-2015)]. Pre- and post-operative stool samples were sequenced using whole-genome shotgun sequencing to identify changes in microbial composition. Diversity indices and differential abundance were calculated, and correlations between dietary intake and outcomes were assessed using linear regression and machine learning models. At the phylum level, pre-operative Synergistetes abundance was positively correlated with soluble fiber intake, and Proteobacteria was inversely linked with HEI-2015 scores. Post-operatively, Lentisphaerae was inversely correlated with dietary glycemic index. The change in Verrucomicrobia abundance was inversely correlated with the change in glycemic index, and the change in Fusobacteria abundance was positively correlated with the change in glycemic index. The changes in several functional gene pathways were positively linked to the change in HEI-2015 scores, the change in soluble fiber intake, and the change in insoluble fiber intake. In adults undergoing bariatric surgery, intakes of specific macronutrients pre-operatively and as a function of the change after surgery were correlated with several microbial phyla, genera, and nutrient-related functional gene pathways.