The effect of oral contraceptive agents on the basal metabolic rate of young women.

ABSTRACT

PIP: The contribution of oral contraceptive (OC) use to inter-individual variation in the basal metabolic rate (BMR) was investigated in two groups of Australian women, 18-31 years old: 24 women who had been using OCs for 6 months or more and 22 women who had never used OCs. There were no significant differences between the groups in terms of age, body mass index, or body composition. BMR was significantly higher in OC users than never-users, even when women with high levels of physical activity (presumed to increase BMR) were excluded from the analysis. In the analysis of covariance, with either body weight or a combination of fat and fat-free mass as covariates, the OC users had a BMR almost 5% higher than never-users (5871 and 5601 kJ/d, respectively). There were no significant differences in BMR between phases of the menstrual cycle. The stimulatory effect of catecholamines on energy expenditure may be responsible, in part, for the observed difference. The stimulatory effect of OCs on BMR was accompanied by a small but significant pressor effect. OC use should be considered in all studies on energy metabolism in women.