1. Clinical Effectiveness Research Group, University of Oslo, Oslo, Norway
2. Clinical Effectiveness Research Group, Oslo University Hospital, Oslo, Norway
3. Section of Gastroenterology, Department of Transplantation Medicine, Oslo University Hospital, Oslo, Norway
4. Department of Endocrinology, Obesity and Nutrition, Vestfold Hospital Trust, Tønsberg, Norway
5. Department of Endocrinology, Morbid Obesity and Preventive Medicine Institute of Clinical Medicine, University of Oslo, Norway
6. Institute of Clinical Medicine, University of Oslo, Norway
7. Institute of Clinical Medicine, University of Tromsø, Norway