How to Find the Best Protein Shake for Intermittent Fasting

📌 Overview and Key Takeaways

This is a Dietitian’s guide on how to find the best protein shake for intermittent fasting.

Discover how to supplement your protein intake while doing intermittent fasting.

Last Updated
Jan 31, 2026

Author and Medical Reviewer

Written by Jack, CNC

Jack is a National Academy of Sports Medicine Certified Nutrition Coach.

Protein Shakes for Intermittent Fasting

Can Protein Shakes Help with Intermittent Fasting?

Intermittent fasting is a simple way of eating that involves cycling between periods of fasting and eating.

Instead of focusing on what you eat, it emphasizes when you eat.

Unlike diets that restrict specific foods or require calorie counting, intermittent fasting is all about the timing of your meals.

There are various approaches, with the 16/8 method being the most popular.

With this approach, you fast for 16 hours and limit your eating to an 8-hour window.

Typically, this means skipping breakfast and consuming all your daily meals within an 8-hour timeframe, like between noon to 8 p.m.

The core concept behind intermittent fasting is to increase the time between your last meal of one day and your first meal the next day.

This shift leads to a drop in your insulin levels and prompts your body to utilize stored fat for energy.

It has gained popularity due to its potential health benefits, including weight loss, enhanced insulin sensitivity, and reduced inflammation.

Protein is an important part of intermittent fasting because it helps maintain muscle mass, supports satiety, and stabilizes energy levels during fasting periods.

• Muscle Preservation: During intermittent fasting there is a risk of losing muscle. Sufficient protein intake can help protect your muscle mass.
• Satiety: Protein keeps you feeling full for longer compared to carbs or fats. This reduces hunger and cravings during fasting periods.
• Energy: Protein provides sustained, long-lasting energy by slowing digestion and supporting stable blood sugar levels.

For protein sources, it is recommended to prioritize foods like eggs, fish, and meat.

Some people, like those with dietary restrictions, might find it challenging to get enough protein from sources like these, however, which is where protein shakes can help.

Adding a protein shake to your eating window is an easy way to ensure that you are meeting your protein goals.

Can You Drink Protein Shakes While Intermittent Fasting?

Drinking a protein shake during fasting hours will break your fast.

You can only drink protein shakes during your eating window.

And exactly when you choose to do so will depend on your preferences and fasting protocol:

• With a Meal: If you follow a protocol like the 16/8 method with an 8-hour eating window, you can have your protein shake as part of a meal or snack during that period.
• After Exercise: If you work out during your fasting hours, consider exercising at the end of your fasting window and drinking a protein shake immediately afterward. This provides essential amino acids for muscle recovery without breaking your fast.
• Near the End of Eating Window: Having a protein shake towards the end of your eating window can help curb hunger during the fasting period.

Finally, before you start chugging protein shakes, it is important to note that not all of them are created equal.

What is the Best Protein Shake for Intermittent Fasting?

Many protein supplements contain ingredients known to cause painful side effects and even long-term health problems.

Among the top offenders are food additives and protein concentrates and isolates.

🚫 Avoid Food Additives

Regularly eating emulsifiers, thickeners, artificial sweeteners, and other ultra-processed additives can alter the composition and function of your gut microbiome (North Clin Istanb, 2019).

These shifts, known gut dysbiosis, contribute to a wide range of chronic diseases, including diabetes and even certain cancers (J Exp Med, 2019).

Gut dysbiosis is so problematic because it causes a cascade of problems, including intestinal permeability, systemic inflammation, impaired nutrient absorption, and reduced short-chain fatty acid (SCFA) production.

⚠️ Here is a list of the most common food additives in protein supplements:

• acacia fiber
• acacia gum
• acesulfame potassium
• artificial flavors
• ascorbic acid
• aspartame
• calcium carbonate
• carrageenan
• cellulose gum
• dextrin
• dicalcium phosphate
• dipotassium phosphate
• erythritol
• gellan gum
• guar gum
• gum arabic
• inulin
• locust bean gum
• maltitol
• maltodextrin
• mono- and diglycerides
• ‘natural’ flavors
• rice bran extract
• rice dextrin
• rice hulls
• rosemary extract
• silica
• silicon dioxide
• sodium alginate
• soluble corn fiber
• sorbitol
• soy lecithin
• sucralose
• sunflower lecithin
• tocopherols
• tricalcium phosphate
• xanthan gum
• xylitol
• zinc oxide

As a rule of thumb, if you could not find an ingredient in nature or make it at home, it is a food additive.

🚫 Avoid Protein Concentrates and Isolates

You should also consider avoiding protein concentrates and isolates.

Most protein powders are made from one or both of these protein sources, which have been mechanically and/or chemically stripped of everything but the protein.

This includes the enzymes, fiber, and other natural digestive aids that help you break them down.

You therefore do not digest them in the same way that you do whole foods, which can affect your gut health.

In fact, studies show that regularly eating protein concentrates and isolates can disrupt your gut microbiome (Nutrients, 2018) and cause the formation of toxic byproducts in your gut (Mol Nutr Food Res, 2024).

So instead of ultra-processed protein concentrates or isolates, look for whole food protein sources like egg whites and almonds.

They are easier to digest and absorb.

Order Samples to see for yourself.

Sources

1. Northern Clinics of Istanbul (North Clin Istanb). Food additives and microbiota. 2019.
2. The Journal of Experimental Medicine (J Exp Med). The gut microbiome: Relationships with disease and opportunities for therapy. 2019.
3. Nutrients (Nutrients). Effect of a Protein Supplement on the Gut Microbiota of Endurance Athletes: A Randomized, Controlled, Double-Blind Pilot Study. 2018.
4. Molecular Nutrition & Food Research (Mol Nutr Food Res). In Vitro Fermentation of Animal and Plant Protein Isolates by the Human Gut Microbiota Under High and Low Carbohydrate Conditions. 2024.

Editorial Guidelines

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This article was written by a Registered Dietitian and reviewed by a Physician Assistant. We rely on peer-reviewed research and trusted medical sources, and regularly update our content to ensure accuracy and clarity.