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.

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. The fat oxidation was higher in the afternoon than in the morning.

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.