Menstrual cycle and basal metabolic rate in women.

Basal metabolic rate, resting metabolic rate (RMR), and energy cost of selected activities were measured in six healthy young women who were participating in a study of protein requirements. The women were confined to a metabolic unit for 92 days during which they consumed a defined formula diet. The basal metabolic rate of the women was 20.7 +/- 2.6 kcal/kg body weight/day and the caloric requirement for maintenance of weight was 38.7 kcal/kg body weight/day. Basal metabolic rate varied significantly with the menstrual cycle. Basal metabolic rate decreased at menstruation and fell to its lowest point approximately 1 wk before ovulation subsequently rising until the beginning of the next menstrual period. RMR was 0.99 +/- 0.16 kcal/kg/h. The energy expenditure while sitting was 1.06 times RMR, while walking it was 2.81 times RMR, and while performing treadmill exercise it was 3.47 times RMR.