BMI and diabetes can affect the gut microbiome composition. Bariatric surgery has large variabilities in the outcome.

Background: Bariatric surgery is often the preferred method to resolve obesity and diabetes, with ~800,000 cases worldwide yearly and high outcome variability. The ability to predict the long-term BMI change following surgery has important implications on individuals and the health care system in general. Given the tight connection between eating habits, sugar consumption, BMI and the gut microbiome, we tested whether the microbiome before any treatment is associated with different treatment outcomes, as well as other intakes (HDL, Triglycerides, etc.).Results: A projection of the gut microbiome composition of obese (sampled before and after bariatric surgery) and slim patients into principal components was performed and the relation between this projection and surgery outcome was studied. The projection reveals 3 different microbiome profiles belonging to slim, obese and obese who underwent bariatric surgery, with post-surgery more different from the slim than the obese. The same projection allows for a prediction of BMI loss following bariatric surgery, using only the pre-surgery microbiome. A different projection is associated with sugar metabolism and A1C levels. Conclusions: - the gut microbiome can be naturally decomposed into main components depicting the patient's development and predicting in advance the outcome. Those may be translated into a better clinical management of obese individuals planning to undergo metabolic surgery.