Heart Rate and Its Variability Are Associated With Resting Metabolic Rate and Substrate Oxidation in Young Women but Not in Men

ABSTRACT Background This study aims to examine the relationship between resting vagal‐related heart rate variability (HRV) parameters and heart rate (HR) with resting metabolic rate (RMR) and respiratory exchange ratio (RER) in young adults. Methods A total of 74 young adults (22 ± 2 years old, 51 women) were included in this cross‐sectional study. HRV was assessed using a HR monitor, whereas RMR and RER were determined by indirect calorimetry. Results Linear regression analyses showed a positive association between HR and RER in women (standardized β = 0.384, p = 0.008), while negative associations were observed between vagal‐related HRV parameters and RER in women (β ranged from −0.262 to −0.254, all p ≤ 0.042). No significant association was found between the abovementioned physiological parameters in men. Conclusion Here, we show that HR is positively associated with RER in young women but not in men, while vagal‐related HRV parameters are inversely related to RMR, therefore suggesting a potential sexual dimorphism between cardiac rhythm and its relationship with markers of cardiometabolic health status. Trial Registration: ClinicalTrials.gov identifier: NCT02365129.