Protein-rich Diet and NAFLD in Bariatric Surgery

Inclusion Criteria: * Morbidly obese subjects with a BMI \>40 kg/m2 who are eligible for bariatric surgery and have accepted to undergo RYGB * Weight stable for at least 6 months before the study (+/- 5 kg within the previous 6 months) * Stable medication * Provision of informed consent Exclusion Criteria: * Patients not eligible for laparoscopic RYGB * Incapacity to give a valid informed consent or unwilling to give the consent * Pregnancy or lactating * Type 2-diabetes mellitus * Significant illness within the two weeks preceding surgery, as judged by the physician. * Obvious infection (bacteria, virus etc) * Major cardiovascular disease * Major gastrointestinal, respiratory, or any hormonal disorders * History of drug addiction and/or alcohol use * Suspected or confirmed poor compliance * Alcohol consumption of \> 20 g per day in the case of women and \> 30 g per day in the case of men for at least 3 consecutive months during the previous 5 years * Presence of hepatitis C or frank cirrhosis.