aDivision of Diabetes, Endocrinology and Gastroenterology, University of Manchester, Manchester

bNuffield Department of Population Health, University of Oxford, Oxford, UK

Correspondence to Deepak Bhatnagar, Division of Diabetes, Endocrinology and Gastroenterology, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PL, UK. Tel: +44 161 275 5180; e-mail: [email protected]