1. Department of Endocrinology and Metabolism; Leiden University Medical Center; Leiden The Netherlands
2. Department of Gastroenterology; Rode Kruis Ziekenhuis Beverwijk; Beverwijk The Netherlands
3. Department of Human Genetics; Leiden University Medical Center; Leiden The Netherlands
4. Department of Surgery; Rijnstate Ziekenhuis, Arnhem; Leiden The Netherlands
5. Department of Surgery; Antonius Ziekenhuis, Nieuwegein; Arnhem The Netherlands
6. Department of Surgery; Sint Lucas Andreas Ziekenhuis, Amsterdam; Arnhem The Netherlands
7. Nederlandse Obesitaskliniek West; Den Haag The Netherlands
8. Department of Surgery; Maxima Medisch Centrum, Eindhoven; The Netherlands