Potential associations between alterations in gut microbiome and obesity-related traits after the bariatric surgery

Background: This study aimed to examine the effects of both obesity and bariatric surgery on gut microbiome, dietary intake, as well as metabolic and inflammatory parameters. Methods: All participants (15 with morbid obesity who had bariatric surgery, 8 with morbid obesity and 11 non-obese) were followed up for a 6-month period with interviews at baseline (M0), at the end of 3 (M3) and 6 months (M6). Dietary assessment was done, and blood and faecal samples were collected. Results: Dietary energy and nutrient intakes as well as serum glucose levels, total cholesterol, low-density lipoprotein (LDL)-cholesterol and high sensitivity C-reactive protein (hs-CRP) levels decreased after surgery (p < 0.05, for each). Participants with morbid obesity had higher levels of Firmicutes and lower levels of Bacteroidetes at M0 compared to non-obese participants. The abundances of Bacteroidetes increased (p = 0.02), whereas that of Firmicutes decreased (p > 0.05) after the surgery, leading to a significant decrease in Firmicutes/Bacteroidetes ratio (p = 0.01). At sub-phylum level, the abundances of Lactobacillus and Bifidobacterium decreased, whereas those of Akkermansia increased after the surgery (p < 0.01, for each). Although participants who were morbidly obese had a distinct profile according to ß-diversity indices at M0, it became similar with the profile of non-obese participants (p > 0.05) at M3 and M6. Similarly, α-diversity indices were lower in subjects with morbid obesity at M0, but became similar to levels in non-obese controls at M6. Conclusion: This study confirmed that bariatric surgery has substantial impacts on gut microbiome's composition and diversity, as well as anthropometrical measurements and biochemical parameters, which were associated with the alterations in dietary intake patterns.