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

Abstract

The use of oral contraceptive agents by women may be a factor that contributes to the observed inter-individual variability in the BMR. We, therefore, measured the BMR, body build and composition in two groups of young women and also assessed their self-reported level of physical activity. One group had been using oral contraceptive agents for a period of 6 months or more (OCA, n 24), while the other group had never used oral contraceptives (NOCA, n 22). There were no significant differences in age, body build or composition. The absolute BMR in the two groups were not significantly different when compared using an unpaired t test (OCA: 5841 (SD 471) Y. NOCA: 5633 (SD 615)kJ/d). However, using an analysis of covariance, with either body weight or a combination of fat and fat free mass as covariates, the OCA group had a BMR almost 5 % higher than that of the NOCA group (OCA: 5871 Y. NOCA: 5601 kJ/d; P = 0.002). When those subjects with high self-reported levels of physical activity were excluded, the difference in BMR between the two groups persisted (P = 0401). An ANOVA of oral contraceptives use and phase of menstrual cycle showed sigmcant differences in BMR with use of oral contraceptives (P=O@O4) but no difference in BMR between phases of the menstrual cyde. In conclusion, the ose of oral contraceptive agents deserves consideration when conducting and analysing data from studies on energy metabolism in young women, as it results in a significantly higher BMR.Basal metabolic rate: Body composition: Oral contraceptive agents Many studies over the years have demonstrated that the intra-individual variability in the BMR is remarkably small, with a CV of about

Impact of the menstrual cycle on determinants of energy balance: a putative role in weight loss attempts

“…One study showed that women who used oral contraceptives had a significantly increased BMR (almost 5%) compared to non-pill users, even after adjustment for differences in body weight and self-reported levels of physical activity. 104 However, this was in contrast to a number of other studies, which reported no difference, 35,100 or even a decrease in daily BMR 102 and EE 88 with the use of oral contraceptives compared to no use. It is therefore not possible to draw any conclusions about the effect of oral contraceptive agents on EE.…”

The validity of predicting the basal metabolic rate of young Australian men and women

“…While acknowledging that our methodology was less than ideal, our cross sectional data showed that the phase of the menstrual cycle had no demonstrable effect on BMR; an observation documented in some longitudinal studies (Weststrate, 1993;Piers et al, 1995). An earlier study in this laboratory had suggested that the use of oral contraceptive agents (OCA) may be another factor that could in¯uence the BMR of women (Diffey et al, 1997). The present study, in a larger group of women has con®rmed those observations, as users of OCA had a signi®-cantly higher BMR when adjusted for body weight or body composition ( Table 2).…”

Does menarche mark a period of elevated resting metabolic rate?

“…A final potential limitation is the lack of control for use of oral contraceptives (OC). Because of the conflicting results in the few published studies comparing metabolic rate in OC users and nonusers (14,15,38), the limited data on the effect of OC use on RMR within the individual (37), and the large number of hormonal formulations of OCs commercially available, we decided not to adjust for OC use in the nine girls who were taking OCs 4 yr after menarche.…”