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.

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