Brown Adipose Tissue Activity in Gilbert's Syndrome

The goal of this case-control study is to investigate energy metabolism and brown adipose tissue (BAT) activity in individuals with Gilbert's syndrome (GS) and controls. The main focus of the study is to analyze: 1. the link between bilirubin metabolism and metabolic health. 2. energy metabolism and body composition in individuals with Gilbert's syndrome and control subjects 3. brown adipose tissue activity in Gilbert's syndrome and healthy controls. Participants will undergo the following investigations: 1. cold exposure 2. PET-CT imaging with 18-F-FDG 3. MRI imaging of liver, abdominal fat and muscle 4. blood sampling 5. indirect calorimetry 6. bioelectrical impedance analysis 7. infrared thermography Researchers will compare individuals with GS and control subjects in terms of metabolic health, body composition and BAT activity.