1. Department of Metabolism, Digestion and Reproduction, Imperial College , London W12 0NN , UK
2. Centre for Obesity Research, University College London , London , UK
3. Clinical Research Unit, Parker Institute, Frederiksberg Hospital , Copenhagen , Denmark
4. Department of General and Bariatric Surgery, Imperial College Healthcare NHS Trust, St. Mary's Hospital , London , UK
5. Department of Urology, Imperial College Healthcare NHS Trust, Charing Cross Hospital , Fulham Palace Road, Hammersmith, London , UK