Since coffee makes you feel revved up, it’s only natural to wonder if it can give you an added boost when you’re fasting. Here’s the thing: There’s no data to either support this idea or shut it down, so it’s really hard for experts to say one way or the other.
Black, unsweetened coffee “increases metabolic rate by about three to four percent,” Keatley says, noting that this can be seen in a very slight increase in your body temperature. “The effect peaks at about 90 minutes after consumption, and it's seen in subsequent cups of coffee as long as they are spaced out by about two to three hours,” he says.
As mentioned, fasting actually slows down your metabolism as your body tries to decrease your metabolic rate to conserve energy. So, while coffee might increase your metabolism slightly during fasting, your body is also operating at a slower speed. Essentially, you’re really not gaining anything special by downing coffee.
Still, your caffeine habit may serve up other benefits unrelated to the scale. Coffee may boost brain health by activating certain neurons and impacting the local release of dopamine, a 1992 study published in Brain Research Reviews found.
Additionally, there's a clear association between increased coffee consumption and a lower risk of developing certain conditions such as cardiovascular disease (CVD), type 2 diabetes, and liver cancer, according to a 2021 study published in Advances In Nutrition. Researchers found that coffee drinks that drank between three to four cups a day significantly reduced CVD risk.
Another study published in 2022 in the European Journal of Preventive Cardiology found that drinking two to three cups of ground, instant, and decaf coffee per day is linked to a longer lifespan.
"The compounds found in coffee may help prevent inflammation and cell damage that causes chronic disease," says Ehsani. IF can also help reduce inflammation, so when you combine drinking coffee with intermittent fasting, you can reduce inflammation in double time, she adds, which may help prevent certain diseases.
What Can I Put in My Coffee That Won't Break My Fast?
But having your coffee black just might not be your ~thing~ and that’s okay. You can add the following to your coffee and still not break your fast, Keatley says:
- A sprinkle of cinnamon
- A touch of nutmeg
- A teensy bit of cocoa
- Low-calorie sweeteners like Splenda