From Gwen Stefani and Cameron Diaz to Jennifer Aniston and Naomi Watts, a new breed of 40- and 50-plus women are redefining not just what an ageless body looks like, but what's entailed in achieving it. A dramatic shift in body expectations in the last few years means that, despite being plagued by a slowing metabolism and a naturally-occurring loss of muscle mass, pre- and post-menopausal women can realistically aim for the healthy, well-functioning body they crave as well as a physique that looks good with a flat stomach and sculpted arms.

Peta Bee and Dr Sarah Schenker are the living embodiment of this new breed of woman: both in their forties with children, both with hectic careers and social lives. And both with the same bodies they had in their 30s. What matters, they have discovered through self-experimentation and trawling the scientific literature, is how you go about holding back the years. And the rules - for both exercise and diet - have changed.