Morbid obesity leads to non-alcoholic fatty liver disease (NAFLD), and not all NAFLD cases benefit from weight loss e.g. after bariatric surgery. Our aim is to find out, which intrahepatic factors and / or biomarkers might be beneficial or can be identified as prognostic factors for remission of NAFLD after weight loss. As other factors such as the microbiome or muscle and fatty tissue also influence the development of obesity and liver diseases, it is planned to examine these parameters before and after bariatric surgery as well.

Tissue biopsies will therefore be taken during the surgery, and blood as well as stool samples will be collected and compared for suitable biomarkers before and after the intervention.

Inclusion Criteria:

• BMI above 40 kg/sqm or
• BMI above 35 kg/sqm and comorbidities related to morbid obesity (e.g. type 2 diabetes, hypertension, coronary heart disease, dyslipoproteinemia, sleep apnea, and others

Exclusion Criteria:

• BMI below 35 kg/sqm
• no informed consent
• patient not suitable for bariatric surgery (severe psychological disorder, pregnancy, drug abuse, active malignant or other consuming disease

Adult Patients with the above given criteria that are willing to treat their morbid obesity by bariatric surgery and have at least absolved 3 months of failed conservative treatment for morbid obesity, have shown to have good long-time compliance and high motivation.