(PTFS20-02-24) Impact of Menstrual and Oral Contraceptive Cycle Phases on Nutrition Intake and Metabolic Flexibility in Sportswomen

Objectives: Fluctuations in energy, macronutrients, and micronutrient intakes in sportswomen in early follicular (EPF), mid-follicular (MFP) and mid-luteal (MLP) phases of the menstrual cycle (MC), and oral monophasic contraceptive (OC) users were recruited in the IronFEMME Study. We explore the effects of the MC and OC cycle on metabolic flexibility (MF) during exercise.

Methods: 40 healthy women who were lean and exercisers (total body mass, 57.69 ± 7.50 kg; body fat, 25.01 ± 6.41 %; VO_2max , 28.42 ± 3.82 L/min), with eumenorrheic MC (n=22) or users of OC’s (n=18), participated in the study. They performed an interval running test (8 bouts of 3 min at 85% of the maximal aerobic speed: vVO_2peak) 2-hour after breakfast. VO_2peak and vVO_2peak were determined by a maximal aerobic test. MC phases were verified by a three-step method. 3-day food records were collected 48h before and 24h after the exercise protocol in each MC/OC phase. Diet was assessed using food records and DIAL software. MF during exercise was calculated as ΔRER, the difference between baseline and last interval respiratory exchange ratio. A one-way ANOVA with Bonferroni post-hoc tests and paired-t-tests were performed to analyze ΔRER across MC or OC phases, respectively. A mixed linear model was used to examine energy and nutrient intake variations across the MC/OC phase, accounting for 3-day food records per phase with subjects as random effects and menstrual/OC phase as fixed effects.

Results: We found a significantly (CI 95%, -0.095 to -0.016; p = 0.008; Cohen’s d=-0.758) greater MF capacity during the hormonal phase (ΔRER, -0.08 ± 0.05) vs. non-hormonal phase (-0.03 ± 0.05) in the OC group. MF did not differ across MC phases, EFP (ΔRER, 0.047 ± 0.05), LFP (0.057 ± 0.087) and MLP (0.056 ± 0.07). Of the 40 participants, only 19 collected 3-day food dietary records (MC, n=12; OC, n=7). No differences in energy and nutrient intake among the groups across phases were found.

Conclusions: Lower estrogen concentration in OC may result in higher MF during exercise compared to phases with higher estrogen levels. Energy and nutrient intake did not vary across MC or OC phases. Additional research is needed to explore the influence of MC, female hormones, nutrient intake, and energy availability on MF during exercise.

Funding Sources: Ministerio de Economía, Industria y Competitividad (Grant code DEP2016-75387-P)