Can You Drink Protein Shakes During Intermittent Fasting? You can have protein shakes while you are on intermittent fasting, but if you drink one outside of your eating window, it will break your fast. Protein shakes is a caloric beverage, and if you eat or drink anything containing calories, you are, by definition, no longer fasting. So, save it for your eating window. You can track all your meals, including your protein shakes, in the Simple app – plus get feedback on your nutrition quality. Protein Shakes During Your Eating Window. If you’re on intermittent fasting, you should look at your protein shake like you would any other food or beverage — save it for your eating window. But during that window consume it however you typically would. Unfortunately, if you work out in a fasted state, you might not be able to drink your shake after you exercise. The jury is still out on which is more important — getting a protein hit right after your workout, or your overall protein consumption for the day. If you want to do both (exercise while fasted and have your post-workout shake), you’ll need to workout near the end of your fasting period.