1. Institute for Evidence in Medicine; Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg; Freiburg Germany
2. Institute for Evidence in Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg; Freiburg Germany
3. Institute of Medical Biometry and Statistics; Faculty of Medicine and Medical Center, University of Freiburg; Freiburg Germany
4. Centre for Obesity and Metabolic Surgery, Center of Surgery, Department of General and Visceral Surgery, Medical Center - University of Freiburg, Faculty of Medicine; Freiburg Germany
5. Department of Anesthesiology and Critical Care, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine and Medical Center, University of Freiburg; Freiburg Germany
6. Institute of General Practice; Medical Faculty of the Heinrich-Heine University; Düsseldorf Germany
7. Centre for Reviews and Dissemination; University of York; York UK