From StairMasters to kettlebells, Rosemary Conley to Natalie Cassidy, we understand and expect that getting in shape is going to require serious effort on our part – and the reverse is true, too, that we expect exercise to pay back the hours of boring, sweaty graft with a leaner, lighter body. Since the days of the Green Goddess, we've known that the healthiest way to lose weight is through exercise. It's science, isn't it?