Can You Drink Protein Shakes While Intermittent Fasting?

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Can You Drink Protein Shakes While Intermittent Fasting

Are you considering the powerful combination of intermittent fasting (IF) and protein shakes to enhance your health and fitness journey? In health and nutrition, few topics have gained as much popularity and controversy as these two.

Intermittent fasting, with its various schedules and methods, has captivated the fitness world, promising various benefits from weight loss to improved metabolic health. Similarly, protein shakes have become universal in gyms and health food stores, praised as essential for muscle growth and recovery.

This article delves into the heart of the matter: can you drink protein shakes while intermittent fasting?

What Is Intermittent Fasting?

Intermittent fasting, as an eating pattern, has gained popularity not only for its potential health benefits but also for its flexibility. Unlike traditional diets that focus on specific foods or portion sizes, intermittent fasting primarily revolves around when you eat.

This flexibility makes intermittent fasting an attractive choice for individuals seeking weight management, improved metabolic health, and potentially even longevity. With a focus on timing rather than food restrictions, it allows for a wide range of dietary choices, including the consumption of protein shakes.

Types Of Intermittent Fasting

Intermittent fasting encompasses a wide range of approaches, each with its own unique fasting and eating windows. Some of the most common ones are:

Overnight Fast

The Overnight Fast, often referred to as the 12/12 method, is one of the simplest intermittent fasting strategies to adopt. This approach emulates your regular daily eating habits to a significant extent. With a 12-hour fasting period and a corresponding 12-hour eating window, it aligns seamlessly with your natural circadian rhythm.

During the Overnight Fast, you consume all your meals and snacks within a set time frame, typically spanning from 6 AM to 6 PM. This time-restricted eating pattern can be relatively easy for many people to adhere to, as it mirrors a conventional eating schedule. It’s particularly well-suited for those who prefer to have their meals during daylight hours.


The 16/8 method is among the most popular time-restricted fasting techniques, known for its simplicity and flexibility. With this approach, individuals allocate an eight-hour window for eating and commit to a 16-hour daily fast. For example, you might restrict your meals to a timeframe like 8 AM to 4 PM, effectively fasting from 4 PM to 8 AM the next day.

This method’s appeal lies in its adaptability to various daily routines. It enables you to choose your preferred eating hours, making it suitable for both early birds who enjoy breakfast and those who prefer later meals. The 16-hour fasting period allows your body to enter a state of fasting, potentially promoting fat burning and other health benefits, while the eight-hour eating window ensures that you consume your daily caloric needs within a concentrated timeframe.

5:2 Diet

The 5:2 diet, also known as the Fast Diet, is a unique approach to intermittent fasting that stands out for its intermittent calorie restriction. Unlike other methods that involve daily fasting windows, the 5:2 diet allows you to eat normally for five days of the week. It’s the two remaining days where a significant change occurs. On these “fasting” days, calorie consumption is restricted to a range of 500 to 600 calories.

This approach to intermittent fasting provides flexibility while promoting calorie reduction. You could, for example, eat without restrictions from Monday to Friday and then limit your caloric intake to 500-600 calories on the weekends. This system can make it more manageable for individuals to adhere to the diet in the long term.

Alternate-day Fasting

Alternate-day fasting is a notable intermittent fasting technique that shares some similarities with the 5:2 diet, but with a more structured and frequent fasting pattern. In this approach, individuals alternate between full feasting days and 500-calorie restricted days on a daily basis.

On feasting days, you’re free to eat without specific restrictions, consuming your regular meals and calories as you typically would. However, on fasting days, your calorie intake is sharply restricted to around 500 calories, which can be challenging but is a key component of this method.

Eat, Stop, Eat

Eat, Stop, Eat is an intermittent fasting strategy that incorporates occasional extended fasting periods into a weekly eating routine. The principle behind this method is relatively simple: you fast for a full 24 hours once or twice a week and eat normally during the remaining five days.

The fasting days are typically chosen at your discretion and can be any day of the week that suits your schedule. You might opt for a 24-hour fast on Mondays and Thursdays, for example, or choose nonconsecutive days that align with your lifestyle. During the fasting period, you abstain from caloric intake entirely, consuming only non-caloric beverages like water, tea, or black coffee.

Whole Day Fast

The Whole Day Fast is an intermittent fasting approach characterized by a highly restricted eating window, typically consisting of just one meal each day. This method is sometimes referred to as the “One Meal a Day” or OMAD fasting plan, and it involves consuming all your daily caloric intake during a single meal.

A common eating window for the Whole Day Fast is in the evening, often with dinner as the designated mealtime. This approach typically requires fasting for approximately 23 hours before that single meal. During the fasting period, you abstain from caloric consumption but may drink non-caloric beverages such as water, herbal tea, or black coffee to stay hydrated.

What Is A Protein Shake?

Protein shakes, once predominantly associated with bodybuilders and athletes, have now found their way into the diets of health-conscious individuals worldwide. They have gained popularity due to their convenience, potential health benefits, and versatility. To understand their nutritional significance, let’s take a closer look at what protein shakes are, their composition, and the various types available.

Protein shakes are dietary supplements or beverages designed to provide a convenient source of protein. They are typically made by mixing protein powder with a liquid, such as water or milk, and often include other ingredients to enhance flavor and nutrition. The primary goal of protein shakes is to increase one’s protein intake, which is essential for various bodily functions, including muscle repair and growth, enzyme production, and immune system support.

Types Of Protein Powder

Protein powders are condensed forms of protein derived from animal or plant sources like dairy, eggs, rice, or peas. Protein powders come in three common forms:  isolates (pure protein with minimal fats and carbs), concentrates (with a more balanced nutrient profile), and hydrolysates (pre-digested for easier absorption)1,2,3.

These protein powders also encompass various types, with common examples including:

Whey Protein (Protein Isolates/Protein Concentrates)

Whey protein is a high-quality protein derived from milk, and it’s a byproduct of the cheese-making process. When cheese is made, an essential step involves curdling milk to separate the solid curds from the liquid whey. Whey is the watery part of milk that remains after curds are formed. It is a rich source of protein, but it’s important to be aware that this type of protein also carries lactose, a milk sugar that some individuals struggle to digest4.

Egg Protein (Protein Concentrates)

Eggs boast the highest protein digestibility-corrected amino acid score, a measure employed to evaluate a protein’s quality and how easily it is digested5.

However, when you opt for egg protein powders, they are usually crafted from egg whites, not the entire eggs. While the protein quality remains high, you might notice reduced satiety since the rich, fatty yolks have been removed.

Hemp Protein (Protein Concentrates)

Hemp protein powder, derived from hemp seeds, is a popular plant-based supplement that offers numerous nutritional benefits. It stands out for its richness in omega-3 fatty acids, which are essential for heart health and brain function. Additionally, hemp protein is a source of essential amino acids, making it a valuable addition to a plant-based diet. However, it is not classified as a complete protein because of its deficient amino acids, lysine, and leucine levels6,7.

Casein Protein (Protein Concentrates)

Casein is a protein found in milk, just like whey. However, it differs in terms of its absorption and processing within the body. Casein is known for its slow digestion and absorption, making it a distinct protein source compared to the faster-absorbing whey protein.

When casein reacts with stomach acid, it creates a gel-like substance, which hampers the quick emptying of your stomach and prolongs the absorption of amino acids into your bloodstream.

It could be more effective in enhancing muscle growth compared to other protein types like soy and wheat8,9.

Pea Protein (Protein Isolates)

Pea protein powder has gained popularity, especially among individuals who follow vegetarian or vegan diets or have dairy or egg allergies or sensitivities. Pea protein is a plant-based protein source derived from yellow split peas. 

Pea protein is absorbed more slowly than whey protein but more quickly than casein, according to animal research from 2015. It may be comparable to dairy protein in terms of its capacity to cause the release of several satiety hormones10.

Can You Drink Protein Shakes While Intermittent Fasting?

The consumption of protein shakes during intermittent fasting should be approached with consideration of its potential impact on the fasting state.

Protein shakes and intermittent fasting can be harmonious if you’re mindful of the timing. Protein is composed of amino acids11 and plays a crucial role in tissue repair, muscle growth, and overall bodily functions12. It also promotes a sense of fullness and reduces hunger due to its longer digestion time13.

However, consuming a protein shake, especially those designed as complete meal replacements, during the fasting period can trigger an increase in insulin levels. This effectively breaks the fast and impedes the utilization of stored fat for energy, potentially counteracting the fasting benefits.

To make the most of both protein intake and intermittent fasting, it’s advisable to enjoy protein shakes within the designated “feasting” or eating window. This approach ensures that your body receives the necessary amino acids and nutrients to support muscle mass and essential bodily functions while preserving the fasting state for maximum fat utilization.

Final Thoughts

When practicing intermittent fasting, protein intake is crucial in preserving muscle mass and supporting your weight loss goals. But while protein shakes provide a convenient way to ensure you meet your required grams of protein, it’s vital to be mindful.

Remember, the timing of when you eat or drink matters during intermittent fasting. Protein shakes, if not taken wisely, can inadvertently break your fast due to their calorie content and impact on insulin levels. Therefore, it is vital to understand how much protein you need and when to consume it.

With mindful consideration of your calorie intake and prudent selection of protein shakes, you can harness their benefits without compromising your fasting periods. Integrating protein shakes into your intermittent fasting regimen can be advantageous, but maintaining a keen awareness of your body’s needs is the key to optimizing your fasting journey.


1 Patel, S. (2015). Emerging trends in nutraceutical applications of whey protein and its derivatives. Journal of Food Science and Technology, 52(11), 6847-6858. https://doi.org/10.1007/s13197-015-1894-0

2 Chaturika Jeewanthi, R. K., Lee, K., & Paik, D. (2015). Improved Functional Characteristics of Whey Protein Hydrolysates in Food Industry. Korean Journal for Food Science of Animal Resources, 35(3), 350-359. https://doi.org/10.5851/kosfa.2015.35.3.350

3 Morgan, P. T., & Breen, L. (2021). The role of protein hydrolysates for exercise-induced skeletal muscle recovery and adaptation: A current perspective. Nutrition & Metabolism, 18. https://doi.org/10.1186/s12986-021-00574-z

4 Zheng X, Shi X, Wang B. A Review on the General Cheese Processing Technology, Flavor Biochemical Pathways and the Influence of Yeasts in Cheese. Front Microbiol. 2021 Jul 29;12:703284. doi: 10.3389/fmicb.2021.703284. PMID: 34394049; PMCID: PMC8358398.

5 Puglisi MJ, Fernandez ML. The Health Benefits of Egg Protein. Nutrients. 2022 Jul 15;14(14):2904. doi: 10.3390/nu14142904. PMID: 35889862; PMCID: PMC9316657.

6 Gorissen SHM, Crombag JJR, Senden JMG, Waterval WAH, Bierau J, Verdijk LB, van Loon LJC. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018 Dec;50(12):1685-1695. doi: 10.1007/s00726-018-2640-5. Epub 2018 Aug 30. PMID: 30167963; PMCID: PMC6245118.

7 FoodData Central. (n.d.). https://fdc.nal.usda.gov/fdc-app.html#/food-details/170148/nutrients

8 Witard OC, Wardle SL, Macnaughton LS, Hodgson AB, Tipton KD. Protein Considerations for Optimising Skeletal Muscle Mass in Healthy Young and Older Adults. Nutrients. 2016 Mar 23;8(4):181. doi: 10.3390/nu8040181. PMID: 27023595; PMCID: PMC4848650.

9 Gorissen SH, Horstman AM, Franssen R, Crombag JJ, Langer H, Bierau J, Respondek F, van Loon LJ. Ingestion of Wheat Protein Increases In Vivo Muscle Protein Synthesis Rates in Healthy Older Men in a Randomized Trial. J Nutr. 2016 Sep;146(9):1651-9. doi: 10.3945/jn.116.231340. Epub 2016 Jul 20. PMID: 27440260.

10 Overduin J, Guérin-Deremaux L, Wils D, Lambers TT. NUTRALYS(®) pea protein: characterization of in vitro gastric digestion and in vivo gastrointestinal peptide responses relevant to satiety. Food Nutr Res. 2015 Apr 13;59:25622. doi: 10.3402/fnr.v59.25622. PMID: 25882536; PMCID: PMC4400298.

11 LaPelusa A, Kaushik R. Physiology, Proteins. 2022 Nov 14. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 32310450.

12 Kreider RB, Campbell B. Protein for exercise and recovery. Phys Sportsmed. 2009 Jun;37(2):13-21. doi: 10.3810/psm.2009.06.1705. PMID: 20048505.

13 Long, S., Jeffcoat, A., & Millward, D. (2000). Effect of habitual dietary-protein intake on appetite and satiety. Appetite, 35(1), 79-88. https://doi.org/10.1006/appe.2000.0332


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