Functional Changes in the Stomach and Esophagus After One Anastomosis Gastric Bypass- OAGB

Inclusion Criteria: * BMI\> 35 kg/m2 * 2 years of controlled conservative obesity treatment without weight reduction * patients should give their consent to participate in the study Exclusion Criteria: * Less than 2 years of conservative obesity treatment * cancer * cirrhosis Child-Pough score A * Crohn's disease * serious psychiatric disorder, which led to in-hospital treatment in psychiatric clinic in the past two years * drug consumption * non-compliance * hiatal hernia \> 4cm * gastric pouch \< 10cm * Barett esophagus * erosive esophagitis Grade C or D according to the Los Angeles Classification * endoscopically proven gastric stricture * acid exposition time \> 6% (Lyon criteria) * reflux episodes\> 80 /24 hours (Lyon criteria) * insufficient low esophageal sphincter according to manometry findings * pathological findings in the impedance pH-metry (acid and non-acid reflux)