One year on, Dr Christian Jessen invites diet swappers back to discover how they're getting on with their new healthy lifestyles, and whether they've finally managed to banish their bad eating habits for good.
Twenty-six-year-old Kevin from Brighton weighed just 8 stone 5 lbs; he was living on coffee, cigarettes, pre-packed sandwiches and takeaways. He regularly skipped breakfast or lunch - or replaced them with chocolate or crisps.
We also catch up with Stefan, a 36-year-old milkman from Northern Ireland. A self-confessed 'carb junkie', Stefan weighed in at 37 stone and was keen to lose weight in a bid to get on the dating scene and boost his confidence.
So how are they both faring 12 months later?
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