Coffee contains caffeine, which is the most commonly consumed psychoactive substance in the world.
Caffeine is also included in most commercial fat-burning supplements today — and for good reason.
Moreover, it’s one of the few substances known to help mobilize fats from your fat tissues and increase metabolism.
But does coffee really help you lose weight? This article takes a close look at the evidence.
Many biologically active substances found in coffee beans find their way into the final drink.
Several of them can affect metabolism:
- Caffeine: The main stimulant in coffee.
- Theobromine: The main stimulant in cocoa; also found in smaller amounts in coffee ().
- Theophylline: Another stimulant found in both cocoa and coffee; has been used to treat asthma ().
- Chlorogenic acid: One of the main biologically active compounds in coffee; may help slow the absorption of carbs ().
The most important of these is caffeine, which is very potent and has been studied thoroughly.
Caffeine works by blocking an inhibitory neurotransmitter called adenosine (, ).
By blocking adenosine, caffeine increases the firing of neurons and release of neurotransmitters like dopamine and norepinephrine. This, in turn, makes you feel more energized and awake.
In this way, coffee helps you stay active when you would otherwise feel tired. In fact, it may improve exercise performance by 11–12%, on average (6, ).
Summary Coffee contains a number of stimulants, most importantly caffeine. Not only does caffeine increase your metabolic rate, it also makes you more alert.
Caffeine stimulates the nervous system, which sends direct signals to the fat cells, telling them to break down fat (8).
It does this by increasing blood levels of the hormone epinephrine (, ).
Epinephrine, also known as adrenaline, travels through your blood to the fat tissues, signaling them to break down fats and release them into your blood.
Of course, releasing fatty acids into your blood does not help you lose fat unless you are burning more calories than you consume through your diet. This condition is known as a negative energy balance.
You can reach a negative energy balance by either eating less or exercising more. Another complementary strategy is to take fat-burning supplements such as caffeine.
Caffeine can also speed up your metabolism, as discussed in the next chapter.
Summary By raising blood levels of epinephrine (adrenaline), caffeine promotes the release of fatty acids from fat tissue.
The rate at which you burn calories at rest is called resting metabolic rate (RMR).
The higher your metabolic rate, the easier it is for you to lose weight and the more you can eat without gaining weight.
Studies show that caffeine can increase RMR by 3–11%, with larger doses having a greater effect (, ).
Interestingly, most of the increase in metabolism is caused by an increase in fat burning ().
Unfortunately, the effect is less pronounced in those who are obese.
One study showed that caffeine increased fat burning by as much as 29% in lean people, while the increase was only about 10% in obese individuals ().
The effect also appears to decrease with age and is greater in younger individuals ().
For more fat-burning strategies, check out this article on 10 easy ways to boost your metabolism.
Summary Caffeine increases your resting metabolic rate, which means it increases the number of calories you burn at rest.
There is one major caveat: people become tolerant to the effects of caffeine over time ().
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, ).
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 of such long-term effects.
Summary People may build up a tolerance to the effects of caffeine. For this reason, drinking coffee or other caffeinated beverages may be an ineffective weight-loss strategy 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, it may be best to cycle your coffee drinking habits to prevent a buildup of tolerance. Perhaps cycles of two weeks on, two weeks off is best.
Of course, there are plenty of other great reasons to drink coffee, including the fact that coffee is one of the single largest sources of antioxidants in the Western diet.