Maximal Fat Oxidation Rate in Healthy Young Adults. Influence of Cardiorespiratory Fitness Level and Sex

Abstract

Introduction

The maximal fat oxidation (MFO) and the exercise intensity that provokes MFO (FATMAX) are inversely associated with cardiometabolic risk factors in healthy young sedentary adults. However, how both cardiorespiratory fitness (CRF) level and sex influence MFO during exercise and the FATMAX is seldom analyzed.

Objectives

This study is aimed at determining the influence of CRF and sex on MFO.

Methods

Twenty healthy young adults (i.e., 12 men and 8 women) completed a graded treadmill protocol to determine MFO, MFO relative to lean mass (MFO_lean), FATMAX and maximum oxygen uptake (VO_2max).

Results

The k-means cluster analysis was used to divide the sample into two different groups for CRF level (56.54 ± 2.54 and 46.94 ± 3.07 mL/kg/min, p < 0.001, respectively). The high-level group revealed higher MFO relative to lean mass (MFO_lean) (3.34 ± 1.44 and 2.73 ± 0.87 g · min⁻¹ · kg, p = 0.001, respectively), and FATMAX in km · h⁻¹ (FATMAX_v) (7.67 ± 0.90 and 7.00 ± 0.97 km · h⁻¹, p = 0.044, respectively) but not for MFO (0.67 ± 0.19 and 0.71 ± 0.20 p = 0.124, respectively). When divided for sex, men exhibited higher values for MFO (0.76 ± 0.21 vs. 0.69 ± 0.19 g · min⁻¹, p = 0.039) and FATMAXv (7.67 ± 0.96 vs. 7.30 ± 0.98 km · h⁻¹, p = 0.036), while women showed higher values for MFO_lean (3.92 ± 1.35 vs. 2.40 ± 0.46 g · min⁻¹ · kg, p = 0.015).

Conclusion

This study highlights the significant influence of CRF level and sex on MFO and FATMAX, offering valuable insights for tailoring exercise programs and optimizing health and performance interventions.