Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax

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Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax

Gutiérrez-Hellín et al., 2020 | Eur J Nutr | Rct

Citation

Gutiérrez-Hellín Jorge, Ruiz-Moreno Carlos, Del Coso Juan. Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax. Eur J Nutr. 2020-Oct;59(7):3341-3345. doi:10.1007/s00394-019-02101-6

Abstract

PURPOSE: p-Synephrine, the principal alkaloid of bitter orange (Citrus aurantium), is widely used in dietary supplements for weight loss due to its purported effect of increasing fat oxidation. However, there is a paucity of scientific information about its effectiveness in enhancing fat oxidation during exercise. The aim of this investigation was to determine the effect of an acute dose of p-synephrine on substrate oxidation during prolonged and constant intensity exercise. METHODS: In a double-blind and randomized experiment, 14 healthy subjects performed two acute experimental trials after ingesting either p-synephrine (3 mg kg-1) or a placebo (cellulose). Energy expenditure and fat oxidation rates were continuously measured by indirect calorimetry during 1 h of continuous cycling at Fatmax, the intensity that induces maximal fat oxidation rate. RESULTS: In comparison to the placebo, energy expenditure during 1 h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123 kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8 g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4 g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small. CONCLUSION: Acute ingestion of p-synephrine augments fat oxidation during prolonged and constant-intensity exercise.

Key Findings

In comparison to the placebo, energy expenditure during 1 h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123 kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8 g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4 g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small.

Outcomes Measured

  • Requires manual extraction

Population

Field Value
Population See abstract
Sample Size See abstract
Age Range See abstract
Condition See abstract

MeSH Terms

  • Adipose Tissue
  • Adult
  • Bicycling
  • Citrus
  • Eating
  • Energy Metabolism
  • Exercise
  • Humans
  • Oxidation-Reduction
  • Synephrine

Evidence Classification

  • Level: Rct
  • Publication Types: Journal Article, Randomized Controlled Trial
  • Vertical: bitter-orange

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09