Sjaak Pouwels1, Hendrika J M Smelt2,3, Johannes F Smulders2,3. 1. Department of Surgery Franciscus Gasthuis & Vlietland, Vlietlandplein 2, 3118 JH, Schiedam, The Netherlands. Sjaakpwls@gmail.com. 2. Department of Surgery Catharina Hospital, Eindhoven, the Netherlands. 3. Obesity Center, Catharina Hospital, Eindhoven, the Netherlands.