Two brides-to-be, weighing in at 6 and 21 stone respectively, trade eating habits in an effort to look their best as they walk down the aisle. Anna Richardson explores the seedy underbelly of extreme dieting, meeting former Big Brother housemate Nikki Grahame to discover the measures she has taken to maintain her physique. Plus, Gillian McKeith helps a group of fat-fighters from Birmingham to shed the pounds. This, the last installment of the series, is followed by the latest episode of The Sex Education Show v Pornography (9.00pm). Tonight, Anna Richardson gives Bristol schoolchildren a live anatomy lesson focusing on the male body. Later, she discovers whether easy access to risque material has led to the 'pornification' of the high street. Plus, erotic actor Damian Duke exposes some of the more unsavoury practices of the adult film industry. Continues tomorrow.