Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women

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first_pagesettingsOrder Article Reprints Open AccessArticle Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women by Jorge Gutiérrez-Hellín 1ORCID,Millán Aguilar-Navarro 1ORCID,Carlos Ruiz-Moreno 2ORCID,Alejandro Muñoz 1,*ORCID,Francisco J. Amaro-Gahete 3ORCID,María Posada-Ayala 4ORCID,Álvaro López-Samanes 5ORCID,Juan Del Coso 6,*ORCID andDavid Varillas-Delgado 1ORCID 1 Exercise and Sport Science, Faculty of Health Sciences, Universidad Francisco de Vitoria, 28223 Pozuelo, Spain 2 Exercise Physiology Laboratory, Camilo José Cela University, 28692 Villanueva de la Cañada, Spain 3 Department of Medical Physiology, School of Medicine, University of Granada, 18071 Granada, Spain 4 Faculty of Experimental Sciences, Universidad Francisco de Vitoria, 28223 Pozuelo, Spain 5 School of Physiotherapy, Faculty of Health Sciences, Francisco de Vitoria University, 28223 Madrid, Spain 6 Centre for Sport Studies, Rey Juan Carlos University, 28943 Fuenlabrada, Spain * Authors to whom correspondence should be addressed. Nutrients 2022, 14(20), 4352; https://doi.org/10.3390/nu14204352 Received: 22 September 2022 / Revised: 11 October 2022 / Accepted: 14 October 2022 / Published: 17 October 2022 (This article belongs to the Special Issue Nutrition and Training Strategies for the Female) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract p-Synephrine is the principal alkaloid of bitter orange (Citrus aurantium). Several recent investigations have found that the intake of 2–3 mg/kg of p-synephrine raises fat oxidation rate during exercise of low-to-moderate intensity. However, these investigations have been carried out only with samples of male participants or mixed men/women samples. Therefore, the aim of this investigation was to study the effect of p-synephrine intake on fat oxidation during exercise of increasing intensity in healthy women. Using a double-blind, randomized experiment, 18 healthy recreationally active women performed two identical exercise trials after the ingestion of (a) 3 mg/kg of p-synephrine and (b) 3 mg/kg of a placebo (cellulose). The exercise trials consisted of a ramp test (from 30 to 80% of maximal oxygen uptake; VO2max) on a cycle ergometer while substrate oxidation rates were measured at each workload by indirect calorimetry. In comparison to the placebo, the intake of p-synephrine increased resting tympanic temperature (36.1 ± 0.5 vs. 36.4 ± 0.4 °C p = 0.033, d = 0.87) with no effect on resting heart rate (p = 0.111) and systolic (p = 0.994) and diastolic blood pressure (p = 0.751). During exercise, there was no significant effect of p-synephrine on fat oxidation rate (F = 0.517; p = 0.484), carbohydrate oxidation rate (F = 0.730; p = 0.795), energy expenditure rate (F = 0.480; p = 0.833), heart rate (F = 4.269; p = 0.068) and participant’s perceived exertion (F = 0.337; p = 0.580). The maximal rate of fat oxidation with placebo was 0.26 ± 0.10 g/min and it was similar with p-synephrine (0.28 ± 0.08 g/min, p = 0.449, d = 0.21). An acute intake of 3 mg/kg of p-synephrine before exercise did not modify energy expenditure and substrate oxidation during submaximal aerobic exercise in healthy active women. It is likely that the increase in resting tympanic temperature induced by p-synephrine hindered the effect of this substance on fat utilization during exercise in healthy active women.