Featherweight father-of-two Colin Hunt barely tips the scales at nine stone by living on chocolate and little else.

Joining him on the five-day diet swap is a supersizer twice his weight, Tracey Hibbert, who binges on bread. Her post-baby weight has rocketed to 18 and a half stone and she is desperate to lose the pounds.

Meanwhile, the Flab Fighters weigh in before heading for the hills for a dog-walking session. Will they bank their calories or binge on a barrel of biscuits?

And in the home of size zero, Anna Richardson discovers where the overweight go to in LA. At a fat-fighting farm she goes for the burn with an extreme workout and meets the residents of Club Bounce, the dating disco for larger lovelies.