The Castle family from Welwyn Garden City are mystified - how can they be putting on weight when they eat mostly healthy, home-cooked food? Using surveillance from cameras in their home, plus private investigators following them outside the house, the Castles are shown what they're really eating. Anna Richardson is on hand to guide them through their discovery, as well as put them on a ten-week healthy-eating regime. Plus, a group of office workers test the theory that by putting sweet treats out of sight, they can be kept out of mind and - more importantly - mouth.