A woman’s body typically has a fat content of 25%, while 15% is normal for males, a difference that is not caused primarily by excercice or strenuous labour. Millions of years ago, when our evolutionary attributes were established, food ressources were probably uncertain and the female body most likely developed its cushion of fat as a reserve supply for nutrition. A mighty 80,000 calories sustains a pregnancy to term, and body fat is utilized in the production of milk. A critical level of adipose flesh is needed to kick off and maintain the cycle of ovulation. Anorectics usually cease to menstruate because they have fallen below the critical level. Professional athletes, too, may temporarily lose their menstrual cycle in the course of converting their ratio of fat to lean muscle. - Femininity, Susan Brownmiller