Scientists from the University of Grenada found 3mg/kg of caffeine - the equivalent of a strong coffee - ingested half an hour before aerobic exercise significantly increases the rate of fat-burning. They also found caffeine’s effects were more pronounced during afternoon sweat sessions.
The findings offer some clarity to what have been complex and nuanced questions – when is the best time to exercise for optimal fat burning? And in what state? While exercising in the morning on an empty stomach has long been recommended for increasing fat oxidation, the scientific basis for this advice was unclear, says lead researcher Francisco J. Amaro.
In the study, 15 men with a mean age of 32 completed an exercise test four times at seven-day intervals. The subjects ingested 3mg/kg of caffeine or a placebo at 8am and 5pm. The conditions prior to each exercise test (hours elapsed since last meal, physical exercise, or consumption of stimulant substances) were strictly standardised and fat oxidation during exercise was calculated accordingly.
"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," says Amaro.
The results also showed greater fat oxidation during exercise in the afternoon than in the morning for equal hours of fasting. That’s worth noting, for it’s generally easier to fast overnight than it is during the day.
The good news for those who prefer to exercise at the crack of dawn is that by throwing caffeine into the mix (given you’re up early, we presume you would drink coffee anyway) you will boost the fat-burning capacity of your session.
But for optimal lard-torching, the findings suggest a combination of a strong coffee (double espresso, perhaps), on an empty stomach (you’ll probably need to skip lunch), in the afternoon works best.