Special Issue "Effect of Phytochemicals on Fat Oxidation during Exercise"

A special issue of Nutrients (ISSN 2072-6643). This special issue belongs to the section "Sports Nutrition".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editor

Dr. Juan Del Coso
E-Mail Website
Guest Editor
Institute of Sport Sciences (ICD), Rey Juan Carlos University, 28943 Fuenlabrada, Spain
Interests: exercise performance; sports nutrition; exercise physiology; anti-doping; genetics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fueling to support the energy demands of contracting skeletal muscle during exercise of more than a few minutes is derived from carbohydrate and fat substrates, while the contribution of amino acids to energy expenditure is usually minimal. Previous investigations have determined that exercise intensity is the main contributor for the selection of carbohydrate or fatty acids as fuel within the muscle. While the rate of carbohydrate oxidation gradually increases with exercise intensity, the association between fat utilization and exercise intensity is explained by an inverted U-shape curve, indicating the moderate-intensity exercise routines should be the primary selection for those seeking to maximize fat oxidation during exercise (although high-intensity exercise might contribute due to its higher post-exercise fat oxidation rating). Other factors such as training status, pre-exercise feeding, the use of certain active components such as phytochemicals, ambient temperature, and even the time of the day might modify the utilization of fat during exercise. 

Phytochemicals are bioactive chemical compounds derived from plants (fruits, beans, vegetables, and grains). Although they lack any energy value, several phytochemicals have been shown as effective in increasing the rate of fat utilized during exercise, normally at the expense of a reduced carbohydrate utilization. The use of phytochemicals, combined with exercise at the right intensity and in the appropriate ambient conditions, might be an effective strategy to maximize fat oxidation during exercise, which can benefit those seeking body fat reduction for either health or aesthetic reasons, but also for athletes seeking body weight reduction in weight-category sports. 

As the Guest Editor of the Special Issue “Effect of Phytochemicals on Fat Oxidation during Exercise”, I kindly invite you to submit a manuscript to Nutrients, one of the most-read and cited research journals in the category “Nutrition and Dietetics”. The goal of this Special Issue is to provide new evidence of the effects of phytochemicals, including but not limited to caffeine and other alkaloids, p-synephrine, catechins, anthocyanins, etc., on fat oxidation rates during exercise. Primarily, we welcome original research articles, especially those that test the efficacy of long-term protocols combining exercise with phytochemicals. However, we will kindly welcome related systematic reviews, meta-analyses, and opinions that help to further our knowledge about the usefulness of phytochemicals in acute and long-term changes in the selection of substrates during exercise.

Dr. Juan Del Coso
Guest Editor

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Keywords

  • caffeine
  • theobromine
  • theophylline
  • catechins
  • anthocyanins
  • synephrine

Published Papers (4 papers)

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Research

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Article
Placebo Effect of Caffeine on Substrate Oxidation during Exercise
Nutrients 2021, 13(3), 782; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13030782 - 27 Feb 2021
Viewed by 2053
Abstract
By using deceptive experiments in which participants are informed that they received caffeine when, in fact, they received an inert substance (i.e., placebo), several investigations have demonstrated that exercise performance can be enhanced to a similar degree as a known caffeine dose. This [...] Read more.
By using deceptive experiments in which participants are informed that they received caffeine when, in fact, they received an inert substance (i.e., placebo), several investigations have demonstrated that exercise performance can be enhanced to a similar degree as a known caffeine dose. This ‘placebo effect’ phenomenon may be part of the mechanisms explaining caffeine’s ergogenicity in exercise. However, there is no study that has established whether the placebo effect of caffeine is also present for other benefits obtained with acute caffeine intake, such as enhanced fat oxidation during exercise. Therefore, the aim of this investigation was to investigate the placebo effect of caffeine on fat oxidation during exercise. Twelve young men participated in a deceptive double-blind cross-over experiment. Each participant completed three identical trials consisting of a step incremental exercise test from 30 to 80% of V.O2max. In the two first trials, participants ingested either 3 mg/kg of cellulose (placebo) or 3 mg/kg of caffeine (received caffeine) in a randomized order. In the third trial, participants were informed that they had received 3 mg/kg of caffeine, but a placebo was provided (informed caffeine). Fat oxidation rates were derived from stoichiometric equations. In received caffeine, participants increased their rate of fat oxidation over the values obtained with the placebo at 30%, 40%, 50%, and 60% of V.O2max (all p < 0.050). In informed caffeine, participants increased their rate of fat oxidation at 30%, 40%, 50% 60%, and 70% of V.O2max (all p < 0.050) over the placebo, while there were no differences between received versus informed caffeine. In comparison to placebo (0.32 ± 0.15 g/min), the rate of maximal fat oxidation was higher in received caffeine (0.44 ± 0.22 g/min, p = 0.045) and in informed caffeine (0.41 ± 0.20 g/min, p = 0.026) with no differences between received versus informed caffeine. However, the intensity at which maximal fat oxidation rate was obtained (i.e., Fatmax) was similar in placebo, received caffeine, and informed caffeine trials (42.5 ± 4.5, 44.2 ± 9.0, and 41.7 ± 10.5% of V.O2max, respectively, p = 0.539). In conclusion, the expectancy of having received caffeine produced similar effects on fat oxidation rate during exercise than actually receiving caffeine. Therefore, the placebo effect of caffeine is also present for the benefits of acute caffeine intake on substrate oxidation during exercise and it may be used to enhance fat oxidation during exercise in participants while reducing any risks to health that this substance may have. Full article
(This article belongs to the Special Issue Effect of Phytochemicals on Fat Oxidation during Exercise)
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Article
The Impact of Decaffeinated Green Tea Extract on Fat Oxidation, Body Composition and Cardio-Metabolic Health in Overweight, Recreationally Active Individuals
Nutrients 2021, 13(3), 764; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13030764 - 26 Feb 2021
Cited by 1 | Viewed by 1789
Abstract
This study investigated the effect of decaffeinated green tea extract (dGTE), with or without antioxidant nutrients, on fat oxidation, body composition and cardio-metabolic health measures in overweight individuals engaged in regular exercise. Twenty-seven participants (20 females, 7 males; body mass: 77.5 ± 10.5 [...] Read more.
This study investigated the effect of decaffeinated green tea extract (dGTE), with or without antioxidant nutrients, on fat oxidation, body composition and cardio-metabolic health measures in overweight individuals engaged in regular exercise. Twenty-seven participants (20 females, 7 males; body mass: 77.5 ± 10.5 kg; body mass index: 27.4 ± 3.0 kg·m2; peak oxygen uptake (V.O2peak): 30.2 ± 5.8 mL·kg−1·min−1) were randomly assigned, in a double-blinded manner, either: dGTE (400 mg·d−1 (−)-epigallocatechin−3-gallate (EGCG), n = 9); a novel dGTE+ (400 mg·d−1 EGCG, quercetin (50 mg·d−1) and α-lipoic acid (LA, 150 mg·d−1), n = 9); or placebo (PL, n = 9) for 8 weeks, whilst maintaining standardised, aerobic exercise. Fat oxidation (‘FATMAX’ and steady state exercise protocols), body composition, cardio-metabolic and blood measures (serum glucose, insulin, leptin, adiponectin, glycerol, free fatty acids, total cholesterol, high [HDL-c] and low-density lipoprotein cholesterol [LDL-c], triglycerides, liver enzymes and bilirubin) were assessed at baseline, week 4 and 8. Following 8 weeks of dGTE+, maximal fat oxidation (MFO) significantly improved from 154.4 ± 20.6 to 224.6 ± 23.2 mg·min−1 (p = 0.009), along with a 22.5% increase in the exercise intensity at which fat oxidation was deemed negligible (FATMIN; 67.6 ± 3.6% V.O2peak, p = 0.003). Steady state exercise substrate utilisation also improved for dGTE+ only, with respiratory exchange ratio reducing from 0.94 ± 0.01 at week 4, to 0.89 ± 0.01 at week 8 (p = 0.004). This corresponded with a significant increase in the contribution of fat to energy expenditure for dGTE+ from 21.0 ± 4.1% at week 4, to 34.6 ± 4.7% at week 8 (p = 0.006). LDL-c was also lower (normalised fold change of −0.09 ± 0.06) for dGTE+ by week 8 (p = 0.038). No other significant effects were found in any group. Eight weeks of dGTE+ improved MFO and substrate utilisation during exercise, and lowered LDL-c. However, body composition and cardio-metabolic markers in healthy, overweight individuals who maintained regular physical activity were largely unaffected by dGTE. Full article
(This article belongs to the Special Issue Effect of Phytochemicals on Fat Oxidation during Exercise)
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Communication
Effects of p-Synephrine during Exercise: A Brief Narrative Review
Nutrients 2021, 13(1), 233; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13010233 - 15 Jan 2021
Cited by 2 | Viewed by 1796
Abstract
The p-synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements [...] Read more.
The p-synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements have been marketed without proper knowledge of their true effectiveness to enhance fat utilization, especially when combined with exercise. However, the effects of p-synephrine on fat oxidation during exercise have been investigated in the last few years. The aim of the current discussion is to summarize the evidence on the effects of p-synephrine intake on fat oxidation and performance during exercise. Previous investigations have demonstrated that the acute intake of p-synephrine does not modify running sprint performance, jumping capacity, or aerobic capacity. However, the acute intake of p-synephrine, in a dose of 2–3 mg/kg of body mass, has been effective to enhance the rate of fat oxidation during incremental and continuous exercise. This effect has been observed in a range of exercise workloads between 30% and 80% of peak oxygen uptake (VO2peak). The p-synephrine has the ability to increase the maximal rate of fat oxidation during exercise of increasing intensity without affecting the workload at which maximal fat oxidation is obtained (Fatmax). The effect of p-synephrine on fat oxidation is normally accompanied by a concomitant reduction of carbohydrate utilization during exercise, without modifying the energy expended during exercise. The shifting in substrate oxidation is obtained without any effect on heart rate during exercise and the prevalence of adverse effects is negligible. Thus, the acute use of p-synephrine, or p-synephrine-containing products, might offer some benefits for those individuals seeking higher fat utilization during exercise at low to moderate intensities. However, more research is still necessary to determine if the effect of p-synephrine on fat oxidation during exercise is maintained with chronic ingestion, in order to ascertain the utility of this substance in conjunction with exercise programs to produce an effective body fat/weight loss reduction. Full article
(This article belongs to the Special Issue Effect of Phytochemicals on Fat Oxidation during Exercise)
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Review

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Review
Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis
Nutrients 2020, 12(12), 3603; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12123603 - 24 Nov 2020
Cited by 2 | Viewed by 4190
Abstract
A number of previous investigations have been designed to determine the effect of acute caffeine intake on the rate of fat oxidation during exercise. However, these investigations have shown contradictory results due to the differences in the exercise protocols used or the co-ingestion [...] Read more.
A number of previous investigations have been designed to determine the effect of acute caffeine intake on the rate of fat oxidation during exercise. However, these investigations have shown contradictory results due to the differences in the exercise protocols used or the co-ingestion of caffeine with other substances. Hence, to date, there is no consensus about the effect of caffeine on fat oxidation during exercise. The purpose of this study was to conduct a systematic review followed by a meta-analysis to establish the effect of acute intake of caffeine (ranging from 2 to 7 mg/kg of body mass) on the rate of fat oxidation during exercise. A total of 19 studies published between 1978 and 2020 were included, all of which employed crossover experimental designs in which the ingestion of caffeine was compared to a placebo. Studies were selected if the exercise intensity was consistent in the caffeine and placebo trials and if these were preceded by a fasting protocol. A subsequent meta-analysis was performed using the random effects model to calculate the standardized mean difference (SMD). The meta-analysis revealed that caffeine significantly (p = 0.008) increased the fat oxidation rate (SMD = 0.73; 95% CI = 0.19 to 1.27). This increment was consistent with a significant (p = 0.04) reduction of the respiratory exchange ratio (SMD = −0.33; 95% CI = −0.65 to −0.01) and a significant (p = 0.049) increase in the oxygen uptake (SMD = 0.23; 95% CI = 0.01 to 0.44). The results also showed that there was a dose–response effect of caffeine on the fat oxidation rate, indicating that more than 3.0 mg/kg is necessary to obtain a statistically significant effect of this stimulant on fat oxidation during exercise. Additionally, the ability of caffeine to enhance fat oxidation during exercise was higher in sedentary or untrained individuals than in trained and recreational athletes. In conclusion, pre-exercise intake of a moderate dose of caffeine may effectively increase fat utilization during aerobic exercise of submaximal intensity performed after a fasting period. However, the fitness level of the participant may modulate the magnitude of the effect of caffeine on fat oxidation during exercise. Full article
(This article belongs to the Special Issue Effect of Phytochemicals on Fat Oxidation during Exercise)
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