Illustration: Olivier Heiligers Last fall, Miriam set a goal: She wanted to lose two pounds. “It sounds so dumb,” she told me. But at only five-foot-two, any little weight gain was visible on her petite frame, she added. If she wanted to slim down the old-fashioned way, she could have. She had done it before. She knew how to white-knuckle her way through the hunger of a 1,200-calorie day. But, she thought, why bother?