Most diets fail because they ignore when you eat, not just what you eat. Dr. Mindy Pelz reveals how women's bodies run on two energy systems—one burning sugar, the other fat—and explains the fasting cycle for women that syncs eating windows to the menstrual cycle, unlocking fat loss, hormonal balance, better sex, and the superpowers hidden in your monthly biology. Women need longer fasts and heavier exercise during days 1–10 of their cycle when estrogen builds, but must reduce fasting intensity and intensity during days 20–28 when progesterone appears, or risk tanking cortisol and losing their cycle.