The Zone Diet. South Beach. A box of P90X DVDs. A glance at my bookshelf would tell you that sensible diets and working out have always been my M.O. The Zone helped me drop those pesky five pounds before my wedding, South Beach got me back into my pre-pregnancy clothes, and I belong to both a gym and the cult of Tony Horton. But three kids, a sedentary desk job, and too many lunches in front of my computer had combined to leave me cranky and stagnating at about 10 to 12 pounds overweight. It all came to a head when I stupidly tried on a bathing suit. At night. In the harsh lighting of a Target dressing room. Vacation was approaching, and then my 20-year high-school reunion. I had to do something different, and quickly. Yes, vanity was spurring me to action, but I’d long felt a nagging worry that I was on an irreversible creep toward obesity.