Summary: Drinking a cup of strong coffee half an hour before exercise, especially in the afternoon, increases fat-burning.
Source: University of Granada
Scientists from the Department of Physiology of the University of Granada (UGR) have shown that caffeine (about 3 mg/kg, the equivalent of a strong coffee) ingested half an hour before aerobic exercise significantly increases the rate of fat-burning. They also found that if the exercise is performed in the afternoon, the effects of the caffeine are more marked than in the morning.
In their study, published in the Journal of the International Society of Sports Nutrition, the researchers aimed to determine whether caffeine–one of the most commonly-consumed ergogenic substances in the world to improve sports performance–actually does increase oxidation or “burning” of fat during exercise. Despite the fact that its consumption in the form of supplements is very common, the scientific evidence for its beneficial claims is scarce.
“The recommendation to exercise on an empty stomach in the morning to increase fat oxidation is commonplace. However, this recommendation may be lacking a scientific basis, as it is unknown whether this increase is due to exercising in the morning or due to going without food for a longer period of time,” explains the lead author of this research, Francisco José Amaro-Gahete of the UGR’s Department of Physiology.
A total of 15 men (mean age, 32) participated in the research, completing an exercise test four times at seven-day intervals. Subjects ingested 3 mg/kg of caffeine or a placebo at 8am and 5pm (each subject completed the tests in all four conditions in a random order). The conditions prior to each exercise test (hours elapsed since last meal, physical exercise, or consumption of stimulant substances) were strictly standardized, and fat oxidation during exercise was calculated accordingly.
Maximum fat oxidation
“The results of our study showed that acute caffeine ingestion 30 minutes before performing an aerobic exercise test increased maximum fat oxidation during exercise regardless of the time of day,” explains Francisco J. Amaro. The existence of a diurnal variation in fat oxidation during exercise was confirmed, the values ??being higher in the afternoon than in the morning for equal hours of fasting.
These results also show that caffeine increases fat oxidation during morning exercise in a similar way to that observed without caffeine intake in the afternoon.
In summary, the findings of this study suggest that the combination of acute caffeine intake and aerobic exercise performed at moderate intensity in the afternoon provides the optimal scenario for people seeking to increase fat-burning during physical exercise.
About this metabolism research news
Source: University of Granada
Contact: Francisco José Amaro-Gahete – University of Granada
Image: The image is in the public domain
Original Research: Open access.
“Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation?” by Francisco José Amaro-Gahete et al. Journal of the International Society of Sports Nutrition
Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation?
There is evidence that caffeine increases the maximal fat oxidation rate (MFO) and aerobic capacity, which are known to be lower in the morning than in the afternoon. This paper examines the effect of caffeine intake on the diurnal variation of MFO during a graded exercise test in active men.
Using a triple-blind, placebo-controlled, crossover experimental design, 15 active caffeine-naïve men (age: 32 ± 7 years) completed a graded exercise test four times at seven-day intervals. The subjects ingested 3 mg/kg of caffeine or a placebo at 8 am in the morning and 5 pm in the afternoon (each subject completed tests under all four conditions in a random order). A graded cycling test was performed. MFO and maximum oxygen uptake (VO2max) were measured by indirect calorimetry, and the intensity of exercise that elicited MFO (Fatmax) calculated.
MFO, Fatmax and VO2max were significantly higher in the afternoon than in the morning (all P < 0.05). Compared to the placebo, caffeine increased mean MFO by 10.7% (0.28 ± 0.10 vs. 0.31 ± 0.09 g/min respectively, P < 0.001) in the morning, and by a mean 29.0% (0.31 ± 0.09 vs. 0.40 ± 0.10 g/min, P < 0.001) in the afternoon. Caffeine also increased mean Fatmax by 11.1% (36.9 ± 14.4 [placebo] vs. 41.0 ± 13.1%, P = 0.005) in the morning, and by 13.1% (42.0 ± 11.6 vs. 47.5 ± 10.8%, P = 0.008) in the afternoon.
These findings confirm the previously reported diurnal variation in the whole-body fat oxidation rate during graded exercise in active caffeine-naïve men, and indicate that the acute ingestion of 3 mg/kg of caffeine increases MFO, Fatmax and VO2max independent of the time of day.
NCT04320446. Registered 25 March 2020 – Retrospectively registered