Long and lanky, 22-year-old Alex Law from Stockport hits the scales at just over ten stone because he barely eats a meal. Tired and exhausted he lives on a diet of caffeine pills supplemented by stodgy cakes and snacks despite holding down the physically demanding job of a plasterer. Dr Christian Jessen decides to hit him where it will hurt most with a stiff warning about his manhood. His diet swap partner Tracy Morgan from Wales has a mouth that's constantly on the move. If she's not talking at the call centre where she works she's snacking, just like Alex, but the trouble is she's snacking before, after and in between her already substantial daily meals which has caused her weight to soar to nearly 20 stone. Deprived of the meals and forced to eat just Alex's snacks she soon realises where she's going wrong. Journalist Anna Richardson meets Isabelle Caro, the actress who unwittingly found herself a worldwide celebrity as the star of a media campaign to highlight the shocking affects of anorexia. And for the first time in her life Gillian McKeith pigs out as she gets a group of ladies from Basingstoke to reduce their rears with a workout at a pig farm followed by trying out the bum-shrinking effects of mud-packs. Does mum know best when it comes to counting calories? The nation's favourite family meals are checked out by supermarket check-out girls for their highest calorie content as Gillian dishes up spaghetti Bolognese, good old-fashioned sausage, mash and gravy, and a traditional roast beef meal.

• Liza Tarbuck
• Anna Ryder Richardson
• Gillian McKeith