Basal metabolic rate of women on the contraceptive pill.

OBJECTIVE To investigate the variability in basal metabolic rate (BMR) of women taking the contraceptive pill, through sequential measurement over the course of one menstrual cycle. DESIGN Randomised. SETTING Metabolic room, School of Biological and Molecular Sciences, Oxford Brookes University. SUBJECTS AND MEASUREMENTS BMR of five weight-stable women taking the contraceptive pill, was measured three to four times each week for a period of five consecutive weeks, BMR was measured using a Douglas bag. RESULTS The pattern of variation in BMR was random for individual subjects throughout the period of measurement. The level of intraindividual variation indicated by the coefficient of variation (CV) ranged from 2.4 to 4.87%. CONCLUSIONS Women taking the contraceptive pill did not exhibit the cyclicity or variation in BMR observed in some normally ovulating subjects. BMR in women taking the contraceptive pill could therefore be considered a 'biological constant'.