Acute Effects of Commercial Yerba Mate Products on Cardiometabolic Responses during Submaximal Cycling: Brewed to Perform?

Background Yerba mate ( Ilex paraguariensis ) is an herb native to South America known for its caffeine and polyphenol content, with suggested benefits for fat oxidation and energy metabolism. However, few studies have evaluated its brewed forms during exercise, particularly across different commercial brands. Objectives This study aimed to evaluate and compare the acute effects of two commercially available brands of brewed yerba mate on substrate oxidation and energy expenditure in healthy and overweight/obese adults during very low- to moderate-intensity exercise. Methods A randomized crossover study comprising 29 healthy adults (15 men and 14 women) consumed 4 different drinks across separate visits: 2 commercially brewed yerba mate brands (AYM and KYM), water, and water with 135 mg caffeine. Following each drink, participants underwent graded cycling exercise while energy expenditure (EE), respiratory exchange ratio (RER), heart rate (HR), and delta efficiency (DE) were measured using indirect calorimetry. Results Both yerba mate brands had similar caffeine concentrations but different phenolic content, yet neither significantly affected EE, substrate oxidation, HR, or DE during exercise compared to control drinks. Sex-based differences emerged, with women exhibiting higher RER and HR at similar workloads, but no drink × sex interactions were found. Obesity status influenced HR, EE, and DE, with obese participants showing altered physiological responses. A significant 3-way interaction (drink × intensity × sex) was observed for RER ( P = 0.013), particularly in men. No drink × obesity interactions were detected. Conclusions Acute ingestion of brewed yerba mate, regardless of brand, did not enhance metabolic or cardiovascular responses during low- to moderate-intensity cycling. Body composition, particularly obesity status, had a more consistent influence on exercise efficiency than the short-term consumption of functional beverages like yerba mate.