It’s one of the world’s most popular beverages. Millions of people, especially those in Western countries, begin the day with a cup of java, both for a caffeine boost and because it’s an enjoyable drink to sip. In fact, Starbucks has built an empire around serving thirsty people piping hot mugs of coffee.
We now know that coffee is linked with surprising health benefits. Studies suggest that coffee drinkers enjoy a lower risk of certain health problems, including cardiovascular disease, Parkinson’s disease, gout, cirrhosis of the liver, type 2 diabetes, and may be at lower risk of certain forms of cancer, including liver cancer. Some people sip coffee because they believe it helps with weight control and, possibly, gives their resting metabolic rate a boost. It would certainly be a boon if caffeine boosted fat burning. What does science say about this?
Coffee, Caffeine, and Metabolic Rate
Caffeine does appear to elevate resting metabolic rate. In fact, a study published in The American Journal of Clinical Nutrition showed that a 100-milligram dose of caffeine increased resting metabolism by 3-4% over a 2.5-hour period – and when the participants consumed caffeine at 2-hour intervals over a half day, resting energy expenditure was boosted by 8 to 11%. So, drinking caffeinated coffee throughout the day can have a substantial impact on resting metabolic rate, equivalent to burning an extra 100 to 200 calories daily for some people.
This study was conducted with coffee, but you might anticipate some boost in metabolism from drinking caffeinated tea. Studies show that caffeinated green tea also triggers a boost in metabolism of as high as 12%. It’s not clear whether the caffeine in green tea is mainly responsible for the increase or whether it’s the combination of caffeine and the catechins naturally found in green tea. So, coffee or green tea may be an effective way to jumpstart your metabolism in the morning.
The News Isn’t All Positive
That coffee boosts resting metabolism sounds like good news for those who struggle with their weight, but don’t assume that drinking coffee necessarily helps with weight loss. Studies show that your body becomes tolerant to the thermogenic effects of caffeinated coffee and the benefits are likely short-lived. Just as you feel energized, and even a bit jittery, when you first start drinking coffee after abstaining for a while, the thermogenic effects of caffeine may be short-lived as well. As you become tolerant to the caffeine in coffee, resting metabolism tends to shift back toward baseline.
One way to avoid tolerance is to cycle caffeine. Rather than drink a few cups of coffee every day consistently, “periodize” your coffee consumption. Drink it for a week to 10 days. Then, take a break to give your body a chance to lose any tolerance its built up. When you drink caffeine after a break of a week or two, it should, again, jumpstart your metabolism. Anything you do consistently, your body tends to adapt to.
Even if you cycle your coffee and caffeine intake to reduce tolerance, drinking coffee alone probably won’t lead to substantial fat loss, although it can help. If you drink it throughout the day, you could conceivably burn an additional 100 to 200 calories daily. That adds up over time, assuming you don’t eat doughnuts with your coffee. However, you still have to avoid the tolerance effect.
Another way caffeinated coffee could help with weight control is by decreasing appetite. There is evidence that coffee curbs the desire to eat and reduces calorie consumption. Interestingly, a study published in the Journal of the American College of Nutrition found that decaffeinated coffee suppressed appetite more than caffeinated coffee, although caffeinated coffee had appetite-suppressive effects as well. In fact, decaf coffee boosted levels of an appetite control hormone, called PPY, more than caffeinated coffee. So, there may be another component in coffee responsible for its appetite suppressive effects, possibly chlorogenic acid. The timing of caffeine intake may be a factor too. One study found that drinking coffee 3 to 4.5 hours before a meal did little to suppress appetite and calorie intake while drinking coffee 0.5 to 4 hours prior to a meal did.
Drawbacks to Drinking Coffee
Coffee may have health benefits and give your metabolism a subtle boost, but it’s not necessarily for everyone. Studies show that 25% of the population has a variant of an enzyme that controls caffeine breakdown. These people, known as slow metabolizers, are more likely to experience side effects such as a rapid or irregular heart rhythm, a sharp rise in blood pressure, or even a heart attack after drinking lots of coffee. These folks can typically tolerate a cup or two a day, but when they drink larger quantities, the risk of adverse effects rises. In fact, a study carried out by the National Institutes of Health, found that slow-metabolizers are at 36% greater risk of heart attack after drinking 4 or more cups of caffeinated coffee daily. A genetic test can tell you if you’re a slow caffeine metabolizer.
Another problem with drinking coffee for weight control is most people don’t drink plain, unsweetened coffee. Instead, coffee becomes a vehicle for cream and sugar, sometimes large quantities. The average Frappuccino is surprisingly high in calories, with an average of around 47 grams of the sweet stuff. Drinking Frappuccinos and other highly sweetened beverages may negate some of the health benefits that coffee offers.
More bad news. Overall, studies don’t show that drinking coffee regularly enhances weight loss. In fact, one study involving 58,000 health professionals found those who boosted their caffeine intake over 12 years actually gained weight. Coffee is far from a reliable weight loss beverage.
The Bottom Line
Coffee is a healthy beverage overall. IT does seem to boost resting metabolic rate and, possibly, reduce appetite. However, drinking coffee won’t necessarily help you lose weight, especially if you’re a habitual drinker that develops tolerance. So, coffee isn’t a magical weight loss beverage, although if you’re a fast metabolizer, it likely has health benefits in moderation. Be sure to avoid high-calorie, sugar-rich coffee concoctions or your coffee habit could lead to weight gain!
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