Astorino et al. had 14 strength-trained men who were regular caffeine consumers perform a strength workout with either 6mg/kg (thanks to Ezhan who pointed me to a type here. It's 6mg not 0.6 as it said before) caffeine or placebo supplement pre-workout. What they found was that
Caffeine intake increased total energy expenditure by 15% (P<0.05), but the additional calories burned was minimal (+27 kcal).Well, I suppose this is about the amount of calories of a small carrot and not really what you would expect from a fat burner.