Bariatric surgery and its impact on the gut flora

Bariatric surgery (BS) is an effective way to treat obesity. Roux-en-Y gastric bypass reduces the gastric volume and bypasses parts of the small intestine so that malabsorption is expected whereas Sleeve Gastrectomy only reduces the stomach’s volume without inducing malabsorption. However, the extent of malabsorption and its consequences for gut health are not well documented. We hypothesize that the different types of BS induce a different degree of malabsorption, which changes the supply of substrates to the colon. This may modify the activity and composition of the microbiota, impact on faecal water toxicity and affect gut health. In a cross-sectional study, we will assess the extent of macronutrient malabsorption 6 months after BS, compared to healthy controls. In parallel, BS patients and a control group of obese patients on a weight loss diet will be included in a one-year follow-up study to analyze the evolution of their colonic fermentation and its impact on gut health. Blood and fecal samples will be collected prior to and at specific time points after BS or weight loss diet. We will characterize the colonic fermentation by analyzing metabolite profiles of the fecal samples, the microbiota composition and bile acid composition and evaluate their capacity to induce toxicity in cultured colonic cells. Also, the contribution of inflammation to toxicity will be measured. With multivariate statistical techniques, we will identify the parameters associated with toxicity.