For Bridget Praytor, every woman's magazine on the supermarket checkout line rack and every weight loss book on the Internet promised magic: a perfect body in a month, if she just followed this week's fad diet. But how long could someone eat only grapefruit, only beef, or only cabbage soup? At the drugstore, boxes of "magic pills" promised "Lose 10 Pounds in a Week " in a huge font that nearly-but not quite-distracted her from the tiny "may cause death or permanent health problems" warning. The gym promised her health and happiness-so why after torturing herself on the treadmill two hours...