(02) IN ACTIVE WOMEN, CORRELATION BETWEEN MEASURED-TO-PREDICTED RESTING METABOLIC RATE RATIO AND COGNITIVE RESTRAINT VARIES BASED ON CONTRACEPTIVE USE

Previous investigations have a reported a correlation between Cognitive Restraint (CR) from the Three-Factor Eating Questionnaire and RMR_ratio, which is the ratio of measured resting metabolic rate to that estimated by a prediction equation. However, the majority of these studies have been conducted exclusively in women who are not using hormonal contraception, limiting the applicability of their findings.

Purpose: The purpose of this study was to compare the relationship between CR and RMR_ratio in women using no hormonal contraception (NAT) versus those using a combined oral contraceptive pill (OCP).

Methods: Sixty-five generally healthy women (35 NAT, 30 OCP) were included in this analysis. Participants in NAT had not used any form of hormonal contraception for ≥6 months, whereas those in OCP had used a combined OCP for ≥6 months prior to enrollment. All participants self-attested to engaging in ≥2 hours of moderate- to vigorous-intensity exercise per week for the past ≥3 months. Participants abstained from all food, fluid, caffeine, and alcohol for ≥8 hours and from exercise for ≥24 hours prior to their visit. Body fat percentage (BFP) was obtained via dual-energy X-ray absorptiometry (Lunar iDXA, General Electric). RMR was measured using a metabolic cart (TrueOne 2400, Parvo Medics) with ventilated hood. After 30 minutes of supine rest, gas was collected for a minimum of ten minutes with the first five minutes discarded. Data were collected until coefficients of variation < 10% for VO₂ and VCO₂ and < 5% for RMR were achieved, with the average of the final five minutes used. CR was assessed using the Three-Factor Eating Questionnaire Revised 18-item form (possible range: 6-24). RMR_ratio values were calculated using five equations (Harris-Benedict 1918; Cunningham 1980 and 1991; De Lorenzo 1999; and ten Haaf & Weijs 2014). As CR scores were considered non-parametric data, correlations were analyzed using Spearman's ρ corrected for multiple comparisons.

Results: Participants (mean±SD age: 22.2±4.0 years, height: 163.3±6.1 cm; weight: 64.4±10.0 kg; BFP: 33.2±6.3%) had an average measured RMR of 1658±203 kcal/day and median CR score of 12 (inter-quartile range [IQR]: 6). CR was similar in both groups (NAT: 14 [6.5]; OCP: 10.5 [5.75]; Wilcoxon test p=0.28). RMR was higher in OCP by 111 kcal/day (NAT: 1607±192; OCP: 1718±202; t-test p=0.03), though body mass and fat-free mass were similar (ps≥0.93). In NAT, Spearman's ρ ranged from -0.37 to -0.25, and a trend toward statistical significance (ps=0.06) was noted when using Harris-Benedict, De Lorenzo, and ten Haaf & Weijs equations. In OCP, Spearman's ρ ranged from -0.20 to -0.12, and statistical significance was not observed using any of the five equations (ps=0.51). CONCLUSIONS: In our population of young, generally healthy, and physically active women, correlations between CR and RMR_ratio were only observed in those not using hormonal contraception. Previous research that has been heretofore limited to naturally menstruating women may not be applicable to those who are using hormonal contraception. PRACTICAL APPLICATIONS: Coaches, healthcare providers, and other practitioners should be aware that relationships between psychometric variables and energetic status may vary based on hormonal contraceptive use in young, physically active women. Future research is needed to explore hypotheses related to the physiological mechanisms underpinning these differences.

Acknowledgements: None