Caffeine is found in almost every commercial fat-burning supplement and for good reason. Its one of the few natural substances proven to aid fat burning.
Several studies show that caffeine can boost your metabolic rate by 3 to 11%
Other studies indicate that caffeine can specifically increase fat burning by as much as 10% in obese individuals and 29% in lean people.
However, its possible that these effects diminish in long term coffee drinkers.