What's the right diet for you. An Horizon special. 1/3.

This programme looks at the nation’s dieting and eating habits by putting overweight volunteers on personalised diets tailored to their genes, hormones and psychology. Part One. Presenters Dr Chris van Tulleken and Professor Tanya Byron describe the volunteer selection process for the trial. Applicants are shown at various assessment days discussing their eating habits and undergoing medical tests that analyse their physical and psychological makeup; 75 volunteers were chosen in total. Volunteers visit Liverpool Hope University’s newly coined Diet Lab for an intensive analysis that ascertains their eating types. Geneticist Dr Giles Yeo explains the first experiment, in which the volunteers’ eating is covertly observed by the experts. Van Tulleken describes the first of their three posited eater types: Feasters - described as those with the smallest levels of hormone GLP1 in their gut. Gut Hormone Specialist Professor Fiona Gribble and Nutrition Scientist Professor Susan Jebb discuss the eating behaviour of several volunteers placed in the Feasters category. Byron describes the second eater type: Emotional Eaters - described as those who eat for psychological reasons. Behavioural Scientist Professor Paul Aveyard tests volunteers in this category by putting them through a driving test to invoke stress. Volunteers have their cortisol levels measured as well as their eating behaviour. Van Tulleken introduces the third eater type: Constant Cravers - described as those who show evidence of key obesity genes which cause an insuppressible desire to eat. Yeo puts the Constant Cravers volunteers through a Group Force Test. Jebb introduces the content of the Feasters personalised diet, consisting of high protein/low glycemic index foods. Gribble puts this diet through a series of analytical tests. Jebb introduces the content of the Constant Cravers diet, which involves fasting and calorie restrictions. Yeo puts the Constant Cravers group through a 2 day fast and analyses their urine for ketones. Jebb introduces the Emotional Eaters personalised diet, based on establishing new healthy eating habits through group support. Aveyard tests this diet using a psychology-focussed abseiling task based around group support.