1. Digestive Diseases and Surgery Institute, Cleveland Clinic London, 33 Grosvenor Pl, London SW1X 7HY, UK
2. Department of Gastroenterology, University College London Hospital Euston Road, London NW1 2BU, UK
3. Centre for Obesity Research, Rayne Institute, Department of Medicine, University College London, London WC1E 6BT, UK
4. Bariatric Centre for Weight Management and Metabolic Surgery, University College London Hospital, London WC1E 6BT, UK
5. Department of Endocrinology and Diabetes, University College London Hospital, London WC1E 6BT, UK
6. National Institute of Health Research, UCLH Biomedical Research Centre, London W1T 7DN, UK