Xand Van Tulleken has got fit. At the same time, his twin brother Chris has descended into a very creaky middle age. Can Xand persuade Chris to do some exercise? Show more

Xand Van Tulleken has got fit. At the same time, his twin brother Chris has descended into a very creaky middle age. Can Xand persuade Chris to do some exercise? Show more

Xand Van Tulleken has got fit. At the same time, his twin brother Chris has descended into a very creaky middle age. Can Xand persuade Chris to do some exercise? Show more

Xand Van Tulleken has got fit. At the same time, his twin brother Chris has descended into a very creaky middle age. Can Xand persuade Chris to do some exercise? Show more

Chris and Xand talk to geneticist Dr Giles Yeo to understand the origins of Xand's size, learning how food environments affect our susceptibility to Ultra Processed Food. Show more

Chris and Xand meet Professor of Chemistry Andrea Sella to understand the lies behind Ultra Processed Food. Show more

Chris and Xand have a conversation about why this project is hard for them. They speak to Alasdair Cant, a behaviour change expert, about how we decide to become different people. Show more

Chris van Tulleken is determined to improve his relationship with his twin brother Xand and, in the process, understand what change is and whether any of us can change who we are. Show more

Chris and Xand take a personality test to find out whether birth order has any effect on our personality. They encourage their immediate and extended family to do the same. Show more

Psychologist Wendy Johnson drills into the contentious debate around nature and nurture and Chris considers how much power he has to change his and Xand’s relationship. Show more

Chris wonders how easily we can harness willpower to make changes in our lives or if it’s an elusive concept. Xand can’t find the willpower to get on his exercise bike. Show more

Chris confronts the changes he needs to make to improve his relationship with Xand, like being a better listener. Xand wants Chris to join him in his pottery shed. Show more

Chris and Xand van Tulleken at the Hay Festival, reflecting on lessons learnt about their health and relationship while recording their podcast, A Thorough Examination. Show more

Xand starts the Ultra Processed Food diet and speaks to obesity expert Dr Janine Makaronidis about the effect of UPF on his body. Show more

Chris and Xand also speak to sensory expert Professor Barry Smith about how companies target our senses with ultra-processed food. Show more

Drs Chris and Xand van Tulleken reflect on a year of personal and professional change. Since completing an ultra-processed food experiment has Xand quit eating junk food for good? Show more

Prof Sarah Garfinkel tests the twins’ ability to interpret their inner emotions with surprising results. Is this why changing and improving their relationship is proving difficult? Show more

The twins meet a social worker helping families to make positive and sometimes urgent changes in their lives. Show more

How chicken got big. Dr Chris van Tulleken unwraps the forces that shape what we eat. This is how we changed chicken - and chicken changed us. Show more

Drs Chris and Xand van Tulleken explore the science of exercise and the dangers of inactivity. Can Xand persuade Chris to do some exercise? Show more