Abstract

Introduction: Studies have shown enhanced fatty acid oxidation (FAO) after ingestion of Yerba Maté (YM) compared to placebo (PL) conditions. Interestingly, this improvement was reported at rest and during exercise. Therefore, the purpose of this study was to investigate the effects of YM ingestion on substrate utilisation (including FAO) during a low-moderate intensity walking exercise test.
Methods: This study was a single-blind randomised control trial with a repeated-measures design. Following institutional ethics approval, seven healthy and active men (n=4) and women (n=3) were recruited. After an initial habitulisation trial and separated by at least 3 days, participants ingested either 1000mg YM or PL capsules 60min prior to commencement of a walking-based cardiorespiratory exercise test. Respiratory data including oxygen uptake ( O2), carbon dioxide production ( CO2) and respiratory exchange ratio (RER) were measured breath-by-breath using an online gas analyser in the last 15min of a 60min pre-exercise resting period. A pre-exercise BL (mmol.l) was also taken. Participants completed a modified Bruce protocol on a treadmill, which was terminated at 85% maximum heart rate (HR). Participants O2, CO2 and RER were measured continuously. Rate of perceived exertion and HR were recorded during the last 30s of each 3min stage and a further BL measurement occurred immediately post-exercise. Using the respiratory data, substrate utilisation was calculated using O2, CO2, RER and stoichiometric equations for FAO (g.min-1) and carbohydrate oxidation (g.min-1). Data was analysed by a factorial repeated-measures ANOVA with post-hoc tests deployed and effect sizes were calculated.
Results: There was no significant difference found for the time (min) to completion of the exercise test (YM=16.43±0.68/ PL=16.29±0.61, t=1.00, P=0.356). YM increased FAO during the exercise test and contrasts revealed significant interactions when comparing to the conditions at 6min (YM=0.58±0.13/ PL=0.35±0.07, F(1,6)=6.733, P=0.041, r=0.53) and 9min (YM=0.66±0.17/ PL=0.43±0.10, F(1,6)=8.565, P=0.026, r=0.59) of the exercise test. These effects reflect that YM ingestion increased FAO significantly more meaningfully at low-to-moderate exercise intensities (29-38% O2peak) than at higher intensities (52-79% O2peak). No statistical differences were found between conditions for all other data (all P>0.05) in the pre-exercise period or at any stage of the exercise test.
Conclusion: This study showed that after YM ingestion, FAO improved during exercise at low-to-moderate intensities during a submaximal exercise test. This study adds to the growing literature on the thermogenic effect of YM, and specifically implies that the supplement has some potential for those attempting weight-loss and fat reduction strategies.