Coffee before exercise increases fat-burning

If the exercise is performed in the afternoon, the effects of the caffeine are more marked than in the morning.


There is proof that Caffeine increases the maximal fat oxidation rate (MFO) and aerobic capacity, which are lower in the morning than in the afternoon. A new study aims to examine caffeine intake’s effect on the diurnal variation of MFO during a graded exercise test inactive men.

Scientists from the Department of Physiology of the University of Granada (UGR) determined whether drinking coffee increases oxidation or “burning” of fat during exercise.

A total of 15 men (mean age, 32) participated in the research. Using a triple-blind, placebo-controlled, crossover experimental design, participants completed a graded exercise test four times at seven-day intervals.

Subjects ingested 3 mg/kg of Caffeine or a placebo at 8 am and 5pm. The conditions before each exercise test were strictly standardized, and fat oxidation during exercise was calculated accordingly.

The lead author of this research, Francisco José Amaro-Gahete of the UGR’s Department of Physiology, said, “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.”

“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. 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.”

The study also shows that Caffeine increases fat oxidation during morning exercise in a similar way to that observed without caffeine intake in the afternoon.

In summary, this study’s findings 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.

Journal Reference:
  1.  Mauricio Ramírez-Maldonado et al, Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation?, Journal of the International Society of Sports Nutrition (2021). DOI: 10.1186/s12970-020-00400-6

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