Chris van Tulleken trained as a doctor at Oxford University, England with his identical twin brother Xand. He specialised in infectious disease and tropical medicine and works at the Hospital for Tropical Diseases in London. Xand van Tulleken trained as a doctor at Oxford University with his identical twin brother Chris. As a specialist in tropical medicine, he has travelled all over the world. He is an active researcher and is the author of the acclaimed book 'How to Lose Weight Well'.