Weighing in at just 6 stone 8 pounds is superskinny working mum Gillian. The 24-year-old Inverness nurse is so busy caring for others she's forgotten how to look after herself and her weight has plummeted.

Her polar opposite is another nurse, 26-stone self-confessed foodie Philippa, whose typical daily supersize menu includes a generous breakfast, followed by burger and fries, Yorkshire pudding and shepherd's pie.

Both women get shocking wake-up calls: Gillian discovers the devastating effects her diet has had on her body and Philippa comes face to face with the consequences of a lifetime of overeating when she meets Lisa, a woman about to undergo life-threatening weight-loss surgery.

Meanwhile, Anna Richardson travels to LA to investigate the continuing obsession with thinness. Back in the UK, she launches her very own Flab Fighters club and teaches a group of serial failed dieters from Newport how to indulge in their favourite treats and still lose weight.