Resting energy metabolism and sweet taste preference during the menstrual cycle in healthy women.

Differences in blood concentration of sex hormones in the follicular (FP) and luteal (LP) phases may influence energy metabolism in women. We compared fasting energy metabolism and sweet taste preference on a representative day of the FP and LP in 20 healthy women (25.3±5.1 years, BMI: 22.2±2.2 kg/m 2 ) with regular self-reported menses and without the use of hormonal contraceptives. From the self-reported duration of the three prior menstrual cycles, the predicted FP and LP visits were scheduled for days 5 to 12 and 20 to 25 after menses, respectively. The order of the FP and LP visits was randomly assigned. On each visit, resting metabolic rate (RMR) and respiratory quotient (RQ) by indirect calorimetry, sweet taste preference by the Monell two-series forced-choice tracking procedure, serum fibroblast growth factor 21 by a commercial ELISA (FGF21, a liver-derived protein with action in energy balance, fuel oxidation, and sugar preference) and dietary food intake by a 24-hour dietary recall were determined. Serum progesterone and estradiol concentrations displayed the expected differences between phases. RMR was lower in the FP vs. LP (1205±110 vs. 1242±117 kcal/d, respectively; P =0.04; Cohen effect size, d rm =0.33), while RQ showed borderline significant higher values (0.84±0.05 vs. 0.81±0.05, respectively; P =0.07; d rm =0.62). Also, in the FP vs. LP, sweet taste preference was lower (12±8 vs. 16±9%; P =0.04; d rm =0.47) concomitant with higher serum FGF21 concentration (294±164 vs. 197±104 pg/mL; P <0.01; d rm =0.66). The menstrual cycle is associated with changes in energy expenditure, sweet taste preference, and oxidative fuel partitioning.