A Thorough Examination with Drs Chris and Xand

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 7 - Have Fun, Feel Good - the twins meet Herman Pontzer, Evolutionary Anthropologist at Duke University and the author of Burn. He explains the science behind metabolism, physical activity and how we really burn calories. Meanwhile, Chris and Xand go to their local park for a game of ping pong. It’s an attempt to find a fun activity that will finally get Chris moving. Unfortunately, ping pong isn’t really Chris’ idea of fun. But what is?

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 6 - Overcoming Barriers - the twins meet Dee Johnson, a therapist experienced in treating addiction disorders, including exercise addiction. She speaks with Xand about how his use of exercise might be straying over into addictive behaviour. Chris is then prompted to examine his own behaviour. What’s really lying behind his reluctance to try and get a bit fitter? We also hear from Xand and his new bride Dolly as they go out cycling on their tandem.

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 5 - Endurance - it’s the day of the big race. Chris tries to run a half marathon, without having done any proper training. It’s an experience that leaves him worrying if he’s ever going to get back into shape. The twins then speak with Alex Hutchinson, writer, runner and author of Endure. Alex explains how pain, resilience and motivation all work together during marathons and other feats of endurance. He also gives Chris some tips on how to bounce back from his marathon ordeal.

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 4 - Too Late to Change? - the twins meet up with their younger brother J for a session on an exercise bike. This has been a big part of Xand’s journey back to fitness. Will it inspire Chris to become more active? Chris then meets up with Sir Muir Gray, Director of the Optimal Aging Programme and an advisor to Public Health England. Muir shows Chris just how important exercise is for an ageing society.

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 3 - Ultra Processed Exercise - the twins meet Danielle Friedman, author of ‘Let's Get Physical: How Women Discovered Exercise and Reshaped the World’. She explains how the fitness industry evolved since the 1950s and how it targets women. Meanwhile, Chris takes a trip to his local gym to start getting into shape for his upcoming half marathon. He also chats with David Colquhoun (Emeritus Professor of Pharmacology at University College London) about their shared suspicion towards exercise and the social pressure to be fit.

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 2 - The Scale of the Crisis - the twins meet Dr Fiona Bull, head of the World Health Organization's Physical Activity Unit. She explains how the WHO is tackling the global inactivity crisis and how schools and cities need to change to meet this challenge. Meanwhile, Xand is still trying to inspire Chris to get more active, so has enlisted his help for a run around their local park. Things don’t quite go according to plan…

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits? In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from. Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living. His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 1 - The Miracle Cure - the twins meet Dr Scarlett McNally, a consultant orthopedic surgeon with a special interest in the benefits of exercise. She explains just how beneficial even moderate exercise can be for our bodies and for the NHS as a whole. Meanwhile, Chris is getting nervous. He has signed up to run a half marathon, but is struggling to do even the most basic training.

Presented by Drs Chris and Xand van Tulleken Producer: Tom Woolfenden Sound Design: Dan King Series Editor: Jo Rowntree

A Van Tulleken Brothers and Loftus Media production for BBC Radio 4

Drs Chris and Xand van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits?

In this series Drs Chris and Xand van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from.

Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living.

His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

The box set is available now on BBC Sounds.

Chris and Xand van Tulleken recorded live at the Hay Festival. They’re reflecting on how much their lives have changed since they started recording their podcast, A Thorough Examination. Xand has lost almost three stone and Chris has written a book about ultra processed food, which was the cause of Xand’s weight gain. They’ve navigated serious health concerns, major bust-ups in their working and personal life and are continuing to challenge their scepticism about each other’s ability to change and improve. In front of a live audience at the Hay Festival, Chris and Xand choose the most memorable moments from series one and two of A Thorough Examination. They revisit Xand’s lowest moments with his weight struggles, Chris’ misguided nagging and reflect on the most useful advice they’ve received from experts. All of this is in the hope that, as they embark on recording series 3 of A Thorough Examination, things will go as smoothly as possible… Recorded live at the Hay Festival, 28th May 2023 Presented by Chris and Xand van Tulleken Produced by Alexandra Quinn A Loftus Media production for BBC Radio 4 and BBC Sounds

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 8 - Changing Our Environment - Xand convinces Chris to come into his pottery shed and give it a whirl. Working together has historically resulted in heated arguments, so it’s time for Chris to act on what he’s learnt about improving his relationship with Xand. The twins consider how easy it is to roll out change on a large scale and ask Will Norman how he manages to implement change in the face of opposition.

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 7 - Changing in a Crisis - the twins speak with Louise, a social worker who supports people every day to make changes in their lives. Chris wants to know how people facing significant obstacles can make positive and successful changes. Louise’s experience prompts Chris to consider the way he approaches improving his relationship with Xand as well as how he advises his own patients.

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 6 - How To Listen To Your Body - Professor Sarah Garfinkel teaches the twins about interoception - or how we understand and act on what’s going on inside our bodies. She tests their ability to interpret their emotions and both Chris and Xand are surprised at the results. Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 5 - Learning To Listen - Chris considers the triggers for his many arguments with Xand and wonders if it might be because he’s not being a good listener. The psychotherapist Erene Hadjiioannou offers Chris some advice on how to react in the heat of an argument. Xand meanwhile is cocooned in his pottery shed contemplating Chris’ complete disinterest in his hobby. He wonders why everyone else in the family shows some enthusiasm, except his twin.

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and Van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 4 - Does Willpower Even Exist? - Chris examines the slippery concept of willpower. Is it something that we all need in order to make personal change and if so, can Chris harness it to encourage Xand to make changes in their relationship? Xand is preoccupied with his exercise bike which stands unused and dusty in his house, can he find the motivation to use it? The psychologist and psychoanalyst Dr Stephen Blumenthal explains willpower in the brain - when does and doesn’t it work?

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 3 - Nature via Nurture - the psychologist Wendy Johnson explodes some home truths around the great nature vs nurture debate. The twins speak to their younger brother J about some changes he’s been trying to implement in his own life that he hopes will improve the way he interacts with his kids. It leaves Chris wondering what he needs to exploit to continue trying to convince Xand to improve their relationship.

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism.

In episode 2 - Does Our Birth Order Affect Our Personality? - the twins find out whether the order in which we’re born has any bearing on our personality. They call their little brother J who lives in New York and reminisce about their childhood. Chris’ wife Dinah and her older sisters debate whether showing off is the reserve of the youngest sibling. And psychologist Laura Botzet shares her findings from studies on the effect of birth order on personality. Does it have any credibility?

Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor: Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism

In episode 1 - The Twin Effect - Dr Clare Llewellyn explains why we should all care about twin studies and the importance of understanding the impact of genetics vs environment on our development. Chris and Xand meet identical twins Mia and Alexandra who were separated at birth. They reflect on their twin dynamic through the years - what has it meant for their development and can they change the dynamic they have now? Presented by Drs Chris and Xand van Tulleken Produced by Hester Cant and Alexandra Quinn Series Editor Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Drs Chris and Xand van Tulleken explore if people can change and how they do it. How much of our personality is genetic destiny and how much are we shaped by the world around us?

A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

It’s been a year since Chris van Tulleken set his twin brother, Xand, a challenge to help him quit his addiction to junk food. Xand had to eat an 80% ultra-processed food (UPF) diet while learning about its health impact. It worked and by the end Xand rejected all those foods he’d previously adored, including his beloved Chinese dumplings. The experiment had an aversion effect, just as Chris had hoped.

But something else happened during the experiment, Chris also had a conversion experience. A podcast about food addiction transformed into a podcast about the twins’ relationship and how best to help someone you love.

In this episode, the twins reflect on their conversion experiences – are they eating better and more importantly, are they getting on better?

Chris speaks to obesity expert Professor Rachel Batterham who tells him how the scientific discourse about UPF has developed since the end of series 1. And the twins go to see philosopher Barry Smith whose professional life has been affected by the twins’ experiment and he tells them why he’s now refusing to work with major food companies as a sensory consultant.

When Xand pops round for tea one evening, Chris’s five-year-old daughter shares some home truths about her dad and uncle’s relationship and it prompts the twins to consider what else they need to improve in their lives.

Presented by Drs Chris and Xand Van Tulleken Production team: Alexandra Quinn, Jo Rowntree, Hester Cant, Dan King and Maia Miller-Lewis

A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4.

With thanks to Voltage TV for use of their archive.

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode 6 - Building an ultra processed world – finishing the experiment, Xand explains that he has had a ‘conversion experience’. Recognising the dangers of UPF, not only to his own health and wellbeing, but to the health and wellbeing of society, he concludes that he no longer has any desire to eat UPF.

Chris and Xand talk to the American Academic and former professor of nutrition, food studies and public health at New York University, Marion Nestle, who explains how UPF is not just a public health issue, it's an environmental disaster. Marion considers and recommends what needs to be done to combat the rocketing levels of obesity – especially in children - while ensuring sustainable healthy food production.

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode five - Building an ultra-processed mind - Xand continues the experiment eating 80% UPF, becoming more aware of what he is eating, and how it is effecting his mind and body. Xand also speaks to Dr Nicole Avena, a food addiction neurologist, about how our brains are affected by UPF in relation to other addictive behaviour. Both Chris and Xand go on to speak to sensory expert, Professor Barry Smith from the University of London, about how all of our senses are targeted by companies when we consume their UPF products.

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode four - Building an ultra-processed body - Xand starts the diet, eating 80% UPF while continuing to learn about it. Chris thinks the diet will work because he’s done it, subsisting on a junk food diet for four weeks while investigating the causes of childhood obesity in a BBC TV documentary. In order to understand the direct effect UPF is having on his body - appetite, hormones and weight - Xand speaks to obesity expert, Dr Janine Makaronidis from University College London. Xand also interviews Dr Kevin Hall from the National Institute of Health in the US about his ground-breaking research into the consumption of UPF. Kevin was the first scientist to prove that UPF causes weight gain.

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode three - How to change? Let it go… - Chris and Xand have an emotional conversation about why this project is important and hard for both of them to undertake. They speak separately to Alasdair Cant, a behaviour change expert, about how we decide to become different people. Alasdair also speaks to Chris about how he, like many family members, may be holding Xand back from making the necessary changes in his life to get healthier.

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode 2 – UPF is not food - Chris and Xand meet Professor of Chemistry Andrea Sella to try to understand some of the more complex ingredients in Ultra Processed Food and the lies they tell us about when we are full and satisfied. Dr Fernanda Rauber was on the team who "discovered" UPF, and explains why it exists and that perhaps we are thinking about it in the wrong way - that it’s not food, it's an industrial formulation of chemicals.

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris and Xand are doctors, scientists and identical twins. Well, not quite identical. Xand is 20kg heavier, clinically obese, and has a Covid induced heart condition.

Chris believes that the reason Xand is overweight is the same reason that most of us in the UK are overweight - Ultra Processed Food or UPF. It’s the main thing that we now eat and feed to our children, but most of us have never heard of it. It’s addictive, highly profitable and the main cause of the global obesity pandemic. It’s destroying our bodies, our brains and the environment.

In this series, recorded during the first coronavirus lockdown of 2020, Chris wants to help his brother quit UPF and get his health back. So, he has a plan. In an attempt to turn Xand's life around, Chris persuades his brother to eat a diet comprising 80% Ultra-processed food while learning about every aspect of it. By doing this, Chris tests two theories - that Xand is addicted to UPF, and that eating more of the stuff while learning about it, will help him quit. Chris believes that the science shows UPF is addictive and harmful to the body, not least by driving excess consumption and weight gain. By speaking with the world’s leading experts on obesity and nutrition, Xand will learn what UPF is made of, how it’s produced, whether it’s addictive, what it does to the human brain and body and how it is the number one force driving global obesity.

In episode 1 - How did we get so different? - Chris and Xand speak to Cambridge University geneticist Dr Giles Yeo to begin to understand the origins of Xand's (and everyone else's) size, learning about the role our food environments play in our susceptibility to UPF. How much is destiny, how much might we be able to control?

Presented by Drs Chris and Xand Van Tulleken Produced by Hester Cant Executive Producers Philly Beaumont and Jo Rowntree A Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4

Chris van Tulleken is on a mission to get his twin, Xand, to quit ultra-processed food.

There’s a growing global addiction to ultra-processed food aka UPF. Chris thinks UPF is driving Xand’s (and everyone else's) weight problem. So, he proposes a simple experiment - that Xand goes on a final week-long UPF binge whilst interviewing the world's leading experts on addiction, food, nutrition and weight. It's the nutritional equivalent of smoking 100 cigarettes whilst going on a quit smoking course. Simple right? Well, it turns out to be far stranger and more emotional than either of them ever imagined...