As part of the study, 15 men (average age 32) exercised four times a week and consumed caffeine before exercise.
Healthy eating experts advise consuming caffeine or strong coffee half an hour before aerobic exercise to burn fat.
The authors of the study claim that the effects are more pronounced when exercising in the afternoon rather than in the morning. Francisco José Amaro-Gate, the lead author of the study, and a physiologist at the University of Granada, noted that the recommendation for increased fasting exercise to increase fatty acid oxidation is common.
However, such a recommendation has no confirmed scientific basis, as it is not known whether this effect is associated with morning exercise or is a consequence of fasting at night.
In the study, 15 men (average age 32) exercised four times a week. They consumed green coffee bean powder at a dose of 3 mg/kg body weight, roughly equivalent to one serving of strong coffee or a placebo in an aqueous solution. All participants completed the test in accordance with the prescribed conditions and consumed caffeine or a placebo 30 minutes before each test at 8:00 a.m. and 5:00 p.m. in random order.
The research team found that consuming a dose of caffeine 30 minutes before aerobic exercise increases fat oxidation during exercise, regardless of the time of day. At the same time, the fat-burning rate was higher in the afternoon than in the morning, with the same duration of fasting. Compared to the placebo, caffeine increased fat oxidation by 10.7% in the morning and 29% in the afternoon. Caffeine increased exercise intensity by 11% in the morning and 13% per day.