Thirty-four-year-old serial dieter Joanne Allen, who weighs in at 19 stone and five pounds, meets 20-year-old fizzy drink addict Guy Sykes, in a swap that's packed with drama and tears.
Joanne travels to the US to meet 37-and-a-half stone Khalila Morse, to share tips and stories about how their weight inhibits their sex lives.
The show tours the residential districts of Las Vegas, where a lack of supermarkets, fresh fruit and veg, and one of the worst exercise rates in America, has created a city that's fast becoming the county's capital for bariatric surgery.
Dr Christian witnesses one of the most extreme and shocking weight-loss procedures on the planet: he meets a man who eats as much as he likes and then fits a tube directly into his stomach to pump out the food.
And recovered anorexic and journalist Emma Woolf meets the family of Jay Taylor, who lost her battle with anorexia in August 2013.
