Depending on your goals and the type of fast you’re doing, drinking beverages with a small number of calories (such as lemon water or coffee) should not interfere with your progress. In fact, taking a “dirty” fasting approach to beverages can make fasting easier to stick with for beginners and help keep your body properly hydrated.
As Varady explains of her clinical experience with fasting, “Many of our studies run 6-12 months, and we want our subjects to feel comfortable while doing fasting. If we ask them to change their eating habits too much, they often drop out.” Plus, she adds, if weight loss is the goal, “these additives only contribute a very small amount of calories, so it does not upset their progress.”
That said, high-calorie or high-sugar options like smoothies, soda, or broth will likely do more harm than good and should be avoided during your fasting window.
And despite the health benefits of fasting, it’s definitely not for everyone. For example, some experts warn that intermittent fasting is trickier for women because fasting is a type of stressor, and women process stress differently than men.
Amy Shah, M.D., a double board-certified physician specializing in hormones, previously told mbg that overly stressed women should skip intermediate fasting, as it can negatively impact female hormones (though more research needs to be done on the subject).