The participants in the group undergoing liver biopsy during bariatric surgery will be asked permission to be approached for follow-up measurements 3 months post-surgery. As they will lose weight, which is associated with improvement of hepatic steatosis, this enables assessment of possible changes over time. A routine follow-up visit post-surgery will take place after 3 months. The follow-up measurements will be combined with this visit, minimizing the burden for the participant. The measurements will consist of blood, faeces and exhaled air collection and a FibroScan (+CAP) will be performed during a study visit. Furthermore, weight, height, BP and abdominal and waist circumference will be measured.