In the third and final week of the diet challenge, Michael explores the connection between comfort eating, and the different ways our brains respond when faced with a bar of chocolate as opposed to a pile of fruit and vegetables. He also has the unique experience of having a camera stuck up his nose to learn about the connection between weight, snoring and the life-limiting condition of sleep apnoea.

It is week two of their very low-calorie diet and the volunteers' tempers are beginning to fray, but Michael gets them doing high-intensity work-outs and yoga. He also explores the connection between obesity and inflammation and the role it is thought to have in almost every major disease and illness, and Michael's wife, author Dr Clare Bailey, shares recipes and food tips that help to build and maintain muscle.

In the first episode, Michael runs a series of tests to find out just how badly lockdown has affected his volunteers' health, before creating a bespoke diet plan for the 21 days. He also tests misconceptions of what a healthy BMI looks like, and explores the cutting-edge research which indicates ties between BMI and survivability from Covid-19.