The menstrual cycle is the scientific term for the physiological changes that occur in fertile women and other female primates for the purposes of sexual reproduction. In this book, the authors discuss the signs and symptoms, psychological/behavioral changes and abnormalities of the menstrual cycle. Topics include the evolution of the menstrual cycle with a focus on the role of the luteal phase, extended sexual receptivity and the concept of concealed ovulation; functional and structural brain alterations associated with menstrual pain; premenstrual dysphoric disorder (PMDD) and premenstrual syndrome (PMS); the fluctuations on appetite and food intake that occur during the female reproductive cycle; and assessing energy intake and physical activity energy expenditure during the menstrual cycle.