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Can You Drink Protein Shakes While Fasting?

6 min read
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Melissa Mitri post Reviewer Melissa Mitri post Reviewer
Verified by Melissa Mitri
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics

Can you drink a protein shake while fasting? Learn if protein shakes break a fast and how to use them to boost your results.

Table of Contents

Intermittent fasting (IF) is an eating pattern usually used for fat loss during which you only eat within a specified time window. Outside of that window, you are not allowed to eat or drink anything besides water or other calorie-free drinks. But what about protein shakes? 

Read this article to learn how fasting works, how you can include protein shakes in your IF protocol, and when the best times are to consume them when fasting. 

Do Protein Shakes Break a Fast?

While following an IF protocol, you may experience some hunger during the fasting window. So, naturally, you might wonder, “Will a protein shake break my fast, even if I only have one sip?” Unfortunately, the answer is yes. 

A fast is considered broken when you consume anything that contains calories. Protein shakes are not calorie-free; therefore, they break fast.

On the other hand, you can have water or non-caloric drinks like black coffee or tea when fasting, as they do not break your fast and might help you curb your appetite. [1] 

That tea or coffee needs to be free of any additives as well, including sugar and artificial sweeteners, during your fasting window.

Can You Drink a Protein Shake While Fasting?

So, can you at least have a protein shake while intermittent fasting if consumed within the feeding window?

Yes. Although you cannot consume protein shakes during the fasting window, you definitely can during the eating window

Protein shakes are a great aid when intermittent fasting, as they are a very quick and easy way to achieve your daily protein target. This is especially important if you are also on a calorie deficit or have a narrow eating window, such as with 20/4 intermittent fasting

Protein also takes more time to digest, helps you stay full longer, and suppresses hunger. [2] [3]

This can all be beneficial to holding you over during your fasting window and making the process easier.

Consuming a high-protein diet can also help you maintain your muscle mass when fasting, especially if you practice resistance training regularly. [4] 

When to Have Protein Shakes During the Eating Window

As mentioned above, having an appropriate protein intake for your needs is essential when fasting, especially if you are also trying to lose weight or maintain your lean mass. 

Below you can find the best times to consume protein shakes while intermittent fasting.

To Break a Fast And Start Your Eating Window

Some people tend to go overboard with their food once they break their fast, which can then lead to a rather unhinged eating pattern or bloating. This could also be why you cannot lose weight on intermittent fasting.

If you do this, too, protein shakes might be a great way to break a fast and prevent you from overeating. Breaking an intermittent fast with a protein shake can help you stabilize your hunger and set you up for a more balanced diet in subsequent meals. [5]

As a High-Protein Snack

When fasting, you can count on protein shakes for a quick and healthy snack that will help you achieve your daily protein target more easily. 

If you’re aiming to lose fat, you can mix your protein powder with water to minimize your calorie intake. If your goal is to build muscle mass, you can mix it with your favorite milk to provide more calories, protein, and other nutrients.

As Occasional Meal Replacement

Protein shakes can be a good meal replacement, especially if mixed with nutrient-dense ingredients or paired with other nutrient-rich foods. 

It is important to note that protein shakes are great if consumed occasionally at mealtimes instead of food, but they should not be a daily meal replacement.

After a Workout

When intermittent fasting, you can have a protein shake straight after a workout during your eating window. If you work out hard before your feeding window, you will need to wait for that feeding window to start to have your shake. 

Is Fasting Only on Protein Shakes Healthy?

Only consuming protein shakes when fasting is not recommended. This is because, in the long run, you will end up missing out on lots of other essential nutrients, which can lead to inadequate nutrition and health problems. 

Most protein shakes mainly provide protein and lack carbohydrates, fats, and other micronutrients like vitamins and minerals. Therefore, if you are going to just consume protein shakes during a fast, it should be done for only a short period and under the supervision of a dietitian or nutritionist to ensure it is safe for you. 

Alternatively, you could have more nutritious shakes, such as meal replacements, as they are usually more nutritionally balanced. You might also like to try specific types of shakes, such as keto shakes, which also provide fats and other micronutrients. 

Of course, you can prepare your own homemade nutritious shakes as well by adding a selection of wholesome ingredients such as berries, chia seeds, oats, nut butter, and so on. 

Despite some shakes being more nutritious than others, whole foods should always make up most of your diet, even when on an IF protocol. 

Wrapping Up

Intermittent fasting is a very popular way to stay healthy, but understanding which foods you can eat on this eating plan can be quite confusing for those who are just starting out. 

Below you can find the key points about how you can include protein shakes in your IF protocol:

  • Intermittent fasting doesn’t allow eating or drinking anything that provides calories during the fasting window. As protein shakes contain calories, they would indeed break your fast if consumed outside of the feeding window.
  • When on an IF protocol, you can consume protein shakes during the feeding window to break intermittent fasting, as a high-protein snack, as a meal replacement, and after a workout.
  • Consuming only protein shakes while doing intermittent fasting can lead to nutritional deficiencies and related health problems if you do it for too long. If done for a short period, only proceed under the supervision of a dietitian or nutritionist.
  • If you want to consume protein shakes during IF, you can aim for more nutritious versions like meal replacements, keto protein shakes, or homemade shakes prepared with a variety of nutrient-rich foods.
Disclaimer This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

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