Coffee contains caffeine... which is the most commonly consumed psychoactive substance in the world.
Caffeine has made its way to most commercial fat burning supplements, for good reason.
It is one of the few substances that is known to help mobilize fats from the fat tissues and increase metabolism.
Coffee isn't just warm black water.
Substances in the coffee beans do make it into the final drink.
In fact, coffee contains several biologically active substances that can affect metabolism:
- Caffeine - a central nervous system stimulant.
- Theobromine and Theophylline - substances related to caffeine that can also have a stimulant effect.
- Chlorogenic Acid - one of the biologically active compounds in coffee, may help slow absorption of carbohydrates (1).
By blocking Adenosine, caffeine increases the firing of neurons and the release of neurotransmitters like Dopamine and Norepinephrine.
Epinephrine travels through the blood, to the fat tissues and send signals to break down fats and release them into the blood.
This is how caffeine helps to mobilize fat from the fat tissues, making it available for use as free fatty acids in the blood.
How many calories we burn at rest is called the Resting Metabolic Rate (RMR).
The higher our metabolic rate, the easier it is for us to lose weight and the more we can allow ourselves to eat without gaining.
Interestingly, most of the increase in metabolism is caused by an increase in the burning of fat (10).
Unfortunately, the effect is less pronounced in those who are obese.
In one study, the increase in fat burning in lean people is as high as 29%, while in obese individuals the increase is about 10% (11). The effect also appears to diminish with age and is more pronounced in younger individuals (12).
Caffeine can improve athletic performance via several mechanisms, one of those being increased mobilization of fatty acids from the fat tissues. Studies show that caffeine can improve exercise performance by 11-12%, on average (13, 14).
In the short term, caffeine can boost the metabolic rate and increase fat burning, but after a while people become tolerant to the effects and it stops working.
But even if coffee doesn't make you expend more calories in the long term, there is still a possibility that it blunts appetite and helps you eat less.
In one study, caffeine had an appetite reducing effect in men, but not in women - making them eat less at a meal following caffeine consumption. However, another study showed no effect for men (17, 18).
Whether coffee or caffeine can help you lose weight in the long term may depend on the individual. At this point, there is no evidence that it can help with weight loss in the long term.
Even though caffeine can boost your metabolism in the short term, this effect is diminished in long-term coffee drinkers due to tolerance.
If you're primarily interested in coffee for the sake of fat loss, then it may be best to cycle it to prevent a buildup of tolerance. Perhaps cycles of 2 weeks on, 2 weeks off.
Of course, there are plenty of other great reasons to drink coffee, including the fact that coffee is the single largest source of antioxidants in the western diet, outranking both fruits and vegetables, combined.