1 Centre for Obesity Research, Department of Medicine, University College London, London WC1E 6JF, UK.
2 Centre for Obesity Research, Department of Medicine, University College London, London WC1E 6JF, UK; Bariatric Centre for Weight Management and Metabolic Surgery, University College London Hospital, London, UK; National Institute for Health and Care Research, Biomedical Research Centre, University College London Hospital, London, UK. Electronic address: r.batterham@ucl.ac.uk.