Combined oral contraceptives and body weight: do oral contraceptives cause weight gain? A primate model.
BACKGROUND We aimed to evaluate whether a six-cycle treatment with oral contraceptive containing 30 mcg of ethinylestradiol (EE2) plus 2 mg of chlormadinone acetate (CMA) (EE2+CMA) alters body weight (BW) and body composition of healthy young women with normal menstrual cycles. The results in treated subjects were compared to those obtained in nontreated women as control. STUDY DESIGN Multifrequency bioelectrical impedance analysis (MF-BIA) was performed in 48 healthy young women during the follicular phase of their menstrual cycle. Of this group, 24 women were treated with EE2+CMA, and the MF-BIA was repeated at the third and sixth cycle of treatment. The remaining 24 women were submitted to the same examinations after three and six cycles without any treatment. Total body water (TBW), intracellular water (ICW), extracellular water (ECW), fat mass (FM) and fat-free mass (FFM) were calculated. Waist-to-hip ratio (WHR), BW, blood pressure, and the plasma concentrations of electrolytes were also measured at each visit. RESULTS Mean FM significantly (p<.05) decreased in the EE2+CMA group from basal levels of 14.23+/-1.03 to 13.51+/-1.09 and 12.71+/-1.02 kg at the third and sixth cycle of treatment, respectively. Stable values were seen in the control group. During observation, other parameters (BW, WHR, TBW, ECW, ICW, FFM) remained unchanged in all subjects. CONCLUSIONS EE2+CMA reduces FM without altering TBW, ICW, ECW. These preliminary results suggest that progestational activity of CMA could balance both fluid retention and weight gain elicited by EE2.