Studying obesity and metabolic syndrome attention is focused more and more on gut microbiota. In humans and animals, bariatric surgery (mainly gastric bypass surgery) lead to alterations of gut microbiota, which seem to be favourable. In this study the investigators aim to examine the effect of different bariatric procedures on composition of gut microbiota.

The human gastrointestinal tract is home to an extremely numerous and diverse collection of microbes communities, collectively termed the "intestinal microbiota". This amazingly complex and poorly understood group of communities has an enormous impact on humans. Indeed, microbiota is considered to play a number of key roles in the maintenance of host health, including aiding digestion of otherwise indigestible dietary compounds, synthesis of vitamins and other beneficial metabolites, immune system regulation and enhanced resistance against colonization by pathogenic microorganisms. Conversely, the intestinal microbiota is also a potent source of antigens and potentially harmful compounds. Schematically, humans can be considered to exist in a state of natural balance with their microbial inhabitants. A shift in the balance of microbiota composition such that it may become deleterious to host health is termed "dysbiosis". Dysbiosis of the gut microbiota has been implicated in numerous disorders, ranging from intestinal such as inflammatory bowel diseases and colorectal cancer to disorders with more systemic effects such as diabetes, obesity, insulin resistance and steatohepatitis. The link between the microbes in the human gut and the development of obesity, cardiovascular disease and metabolic syndromes, such as type 2 diabetes, is becoming clearer but, because of the complexity of the microbial community, the functional connections are less well understood.

In humans and animals, bariatric surgery (mainly gastric bypass surgery) lead to alterations of gut microbiota, which seem to be favourable. In this study the investigators aim to examine the effect of different bariatric procedures on composition of gut microbiota.

Inclusion Criteria:

• 30 healthy controls: BMI 18-30kg/m2 good general health
• 40 morbidly obese patients (BMI >35kg/m2) scheduled for either sleeve gastrectomy or gastric bypass surgery

Exclusion Criteria:

• Antibiotic therapy within the last 2 months before enrolment
• regular intake of proton pump Inhibitors (PPI)
• previous surgery on the gastrointestinal tract (appendectomy acceptable)