Can you drink coffee during intermittent fasting?
Black coffee fits perfectly well within intermittent fasting and, certainly with moderate use, is not bad for your heart. If you add a significant amount of milk or sugar, that counts as a calorie intake and breaks the fasting window.
Coffee fits perfectly within intermittent fasting. In a recommended dietary pattern that combines time-restricted eating with a Mediterranean diet, water, coffee and tea are explicitly mentioned as suitable drinks during the fasting window. That applies to tea as well.
Moderate coffee consumption, up to roughly three to five cups per day, does not come at the expense of your health. Multiple studies actually link this level of coffee intake to a lower risk of heart problems and stroke, compared with drinking no coffee at all. Coffee contains antioxidants and appears to have a mild anti-inflammatory effect.
Coffee does have no calories when you drink it black. If you add milk, cream or sugar, that is strictly speaking no longer fasting, because those additions activate digestion and insulin production. Whether that negates the benefits of intermittent fasting depends on how much you add, but as a straightforward rule of thumb: black coffee fits within the fasting window, coffee with a substantial number of calories does not.
A word of caution: intermittent fasting is not suitable for everyone. If you are pregnant, breastfeeding, still growing, or using insulin or other medication for diabetes, fasting protocols may carry risks. In those cases, discuss it with your doctor first.
Claims are based on three PMIDs (40504596, 37712135, 32943166), observational and associative in nature. Whether coffee disrupts the fasting effects of intermittent fasting is not directly examined in the available studies. The recommendation to allow coffee within time-restricted eating comes from a single source (PMID 32943166).