Placebo Effect of Caffeine on Substrate Oxidation during Exercise

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 ‘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.

Effects of Different Doses of Caffeine Supplementation on Collegiate Male Volleyball Players’ Specific Performance and Skills: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

“…It is suggested that future studies pay more attention to the interaction of CYP1A2 genotype and caffeine ergogenic responses. It should be noted that the present study compared the effects of caffeine only with the placebo, while it has been shown that placebos have had ergogenic effects on performance compared with control conditions [ 64 , 65 , 66 , 67 ]. It is possible that due to the limitation of the present study design (lack of control conditions), the significant effects of caffeine on handgrip strength or upper-body explosive power are hidden compared with the control conditions.…”

Repeated mouth rinsing of coffee improves the specific-endurance performance and jump performance of young male futsal players

“…Therefore, the improvement of FIET and vertical jump performance may be partly due to placebo ergogenic effects. Some previous studies have also confirmed that the ergogenic or physiological effect of the placebo can be comparable to caffeine [ 44–47 ], but others have not reported a significant effect [ 48 ]. Using deceptive interventions, it has also been reported that a placebo enhanced performance when participants were informed that the substance they were consuming was caffeine [ 46 , 47 ].…”

The effect of beetroot juice Beta Vulgaris L. supplementation on ṼO2max of youth soccer athletes

“…Placebo effect is a phenomenon that occurs when an inert substance is given instead an active medication, but individuals are convinced that they had received the active substance. 27 Environmental and psychosocial determinants are two main factors for the placebo effect . 28 These two factors also include conditioning, verbal suggestions, and habits of health workers (in this case researchers).…”