Forty-two-year-old Mark's daily diet of mountains of greasy food has left him 11 stone overweight. He goes head-to-head with self-conscious food casualty Dale who weighs less than ten stone. Mark Hughes is a heart attack waiting to happen. His continuous consumption of greasy mountains of food has left him weighing 22 stone 3lbs. He's not slept in the marital bed for seven years because of his loud snoring, and relations with his wife are becoming tense. He's checked into the feeding clinic as a last ditch attempt to shift some pounds and start becoming an active dad again. Mark's diet-swap partner is 21-year-old Dale who's been running his body on empty and now weighs a lightweight nine stone six lbs. His skinny frame has knocked his self confidence and left his family worried. Dale wastes no time getting stuck into Mark's colossal portions but the mountains of grease and fat soon turn his stomach - and he just can't keep it down! This sickening wake up call helps Mark realise just how appalling his diet really is. Plus the show's eating disordered group are challenged to confront their distorted body images with a day of clothes shopping. It's a struggle for all of the girls but particularly the youngest member of the group Erin, who has an emotional realisation about the extent of her illness.

• Liza Tarbuck
• Anna Ryder Richardson
• Gillian McKeith