1. Centre for Obesity Research; Rayne Institute; University College London; London UK
2. University College London Hospital Bariatric; Centre for Weight Management and Metabolic Surgery; London UK
3. Department of Epidemiology & Public Health; London UK
4. Health and Social Surveys Research Group; Research Department of Epidemiology and Public Health; University College London; London UK
5. Department of Endocrinology; Imperial College Healthcare NHS Trust; London UK
6. Clinical and Experimental Surgery Department; Medical Research Institute; University of Alexandria; Alexandria Egypt
7. Department of General Surgery; Centro Hospitalar de Entre o Douro e Vouga; Santa Maria da Feira Portugal
8. Clinical and Experimental Endocrinology; Department of Anatomy; Multidisciplinary Unit for Biomedical Research (UMIB); Instituto de Ciências Biomédicas Abel Salazar; University of Porto; Porto Portugal
9. Endocrine Unit; Centro Hospitalar de Entre o Douro e Vouga; Santa Maria da Feira Portugal
10. National Institute of Health Research; University College London Hospital Biomedical Research Centre; London UK