Altered microbiota has been linked to many diseases. The abnormal Set-Point in the Obese may in part be a result from dysbiosis. Many mechanistic connections have been postulated but currently the science is not clear. Bariatric surgery may help in changing the Set-point by changing the microbiome . Gastric bypass in humans has been shown to alter the microbiome. In mice the lasting weight loss effects (i.e. change in set point) of sleeve gastrectomy have been shown to be dependant on bile salt dynamics and subsequent change in gut flora. This paper will explore the current state of knowledge of bariatric surgery and the post-operative microbiome.