Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women.
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2022
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Nutrients
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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 psynephrine
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.
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Sports nutrition, Phytochemical, Weight loss, Endurance exercise, Women athletes