Can You Drink Protein Shakes While Fasting?

by Mara Welty March 13, 2023 6 min read

 clock on a plate surrounded by knife and fork


Many diets and protein plans consider protein shakes to be an essential nutritional supplement, if not a total and healthy meal replacement. And for good reason — protein shakes represent a convenient, cost-effective way to consume the vital nutrients a person needs to lose fat and put on muscle.  

In recent years, intermittent fasting has become wildly popular in the world of health and fitness, with both elite athletes and average Joes embracing this eating pattern to enhance their fitness and weight goals.

But how do protein powders or shakes fit into this type of plan? Can you drink a protein shake during intermittent fasting and still reap the benefits from the fast? Can a protein shake replace a meal?

The answer here depends on when you have the shake. 

However, before we can delve into the proper relationship between fasting and protein shakes, we must first break down the intermittent fasting process.  

What Is Intermittent Fasting?

Fasting is not a novel methodology. 

It has been practiced by various cultures for millennia, both for practical reasons, such as food scarcity and for religious reasons, such as to meditate and focus on spiritual reflection.

As the name implies, intermittent fasting is a staccato-like eating pattern that alternates between periods of eating and fasting, with the individual limiting food consumption to certain hours of the day to trigger fat-burning processes. During the fasting period, only water, tea, coffee or non-caloric beverages may be consumed. 

With intermittent fasting, it’s not about what you eat, but when you eat (or drink a protein shake). 

Depending on your intermittent fast plan, you may break up your day or even the week into periods of fasting and eating. That said, most people that try this eating pattern will opt for one of three methods:

  • Leangains Protocol – This method was developed by personal trainer and nutritionist Martin Berkhan. Sometimes referred to as the 16/8 method, it involves a 16-hour fast followed by an 8-hour feeding window. So, you typically don’t break your fast until 1 pm and then consume all your daily calories by 9 pm.
    • This method also emphasizes resistance training. It recommends that individuals lift weights at least 2–3 times a week during the feeding window. 
  • Eat-stop-eat – This option was designed by fitness expert and author, Brad Pilon. It involves eating normally throughout the day but having one or two days of full fasting each week. 
  • The 5:2 Diet – For those that feel as if the eat-stop-eat plan is too intense, there’s the 5:2 diet, which is a similar, albeit less restrictive method. For five days out of the week, a person eats a normal, healthy diet. And for the other two non-consecutive days, the individual would consume approximately 500–600 calories.  

Why Do Experts Recommend Intermittent Fasting?

Although these methods differ, their ultimate goal is the same — to foster weight loss and spur muscle growth.

But why would intermittent fasting make that occur? 

It comes down to a physiological process known as metabolic switching. 

Given enough time without food, the body will run out of stored glucose-based (sugar) energy. When that energy source is exhausted, the metabolism switches over to ketone-based (fat) stored energy.  

This was an evolutionary biological feature humans developed as hunter-gatherers that allowed them to go without food for hours, if not days, while still having the energy necessary to track down game or scavenge for food. 

The process used to occur naturally. But as Mark Mattson — an esteemed neuroscientist at Johns Hopkins whose research centers on intermittent fasting — notes, modern diets and sedentary lifestyles typically run counterintuitive to this eating pattern:

“Intermittent fasting contrasts with the normal eating pattern for most Americans, who eat throughout their waking hours. If someone is eating three meals a day, plus snacks and they’re not exercising, then every time they eat, they’re running on those calories and not burning their fat stores.” 

Besides fat burning, what are the known benefits of intermittent fasting? 

Over the course of two decades studying this phenomenon, Mattson and company have concluded the following health benefits:

  • Boosts cognition and memory
  • HGH levels skyrocket 
  • Insulin levels drop dramatically 
  • Improves blood pressure and resting heart rate for better heart health
  • Enhanced physical performance with fat loss and muscle growth
  • Reduced tissue damage due to cellular repair   

So, Can You Drink Protein Shakes While Fasting?

The answer to this question is yes and no. Now, if you’re wondering if you can drink protein shakes every day while fasting, drinking protein shakes during an intermittent fast is okay, but only during the appropriate consumption window.

Protein is made up of amino acids. Consuming a protein shake, especially one that's considered to be a full meal replacement, during a fasting period can cause a spike in insulin levels, breaking the fast and preventing the body from burning stored fat for energy.

Are Protein Shakes a Smart Diet Choice During the “Eat Window?”

Protein tends to be great for weight loss support since the body digests protein much more slowly than carbs, which leaves a person feeling full for longer. And, protein can change the levels of hormones that control appetite. 

Even so, whether you should drink a protein shake during the non-fasting window will depend on the type of protein shake. According to Julie Upton, RD and registered dietitian:

“Protein shakes are a convenient source of fuel but can be loaded with sugar or artificial sweeteners. If you do choose a protein shake during your eating period, read the label carefully and check the ingredient list and nutrition facts panel. For best muscle-building and appetite-taming results, mix up your protein sources and spread them out as evenly as possible during eating windows.”

Today, there are hundreds of protein shakes available. Some are formulated solely to provide protein and not much else. Others are made to be total meal replacements. 

For instance, INVIGOR8’s Super Food Shakes were made to provide all of the essential nutritional complexes a person needs for a healthy diet — whether they’re intermittent fasting or eating normally. This includes eight key nutritional complexes: 

  1. Cognitive complex – 200mg of l-theanine and bacopa monnieri.
  2. Digestive enzyme complex – 653mg of amylase, lactase, neutral protease, lipase, bromelain and papain.
  3. Essential fatty acid complex – 2g of flaxseed, chia seed and coconut.
  4. Green veggie complex – 2.5g of chlorella algae, alfalfa grass, spinach leaf, kale leaf and broccoli head.
  5. Immunity support complex– 500mg of bovine colostrum.
  6. Prebiotic-fiber complex – 3g of chicory root extract.
  7. Probiotic complex – 1.2 billion lactobacillus acidophilus and bifidobacterium bifidum. 
  8. Total protein complex – 20g of premium grass-fed whey protein.

Consuming the Super Food Shake during an eating window would provide high-quality sustenance that an active adult requires to meet their macro nutritional requirements.  

What Are the Benefits of Protein Shakes?

If a person consumes the right type of protein shake during the “eat window,” these drinks can offer several advantages, including: 

  • Convenience – After spending all day not eating, the last thing you may want to do is spend time prepping and cooking. And that might not even be possible when you’re at work. With protein shakes, you have a high-quality protein source that only takes a few minutes to prepare, thus ensuring that you can hit your macros no matter where you are. 
  • Cost – The price of protein-based healthy foods has skyrocketed over the past year, especially dairy and meat products. Meal replacement protein shakes can provide the same nutritional value at a fraction of the cost. 
  • Better recovery and muscle building – Your body depends on protein sources to build muscle mass and repair damaged tissue. Protein shakes, especially when consumed directly after an intense workout, can help support an active lifestyle.  

How Much Protein Would You Need To Consume During the Eating Window?

How much protein a person needs to consume during the eating portion of the intermittent fast will depend on the individual’s body, needs, goals and activity levels. 

For example, doctors generally recommend that active adults who want to build muscle and lose fat should consume approximately 1.2-1.6 grams of protein for every kilogram of their target body weight; whereas, sedentary adults should only consume .8 grams of protein for every kilogram.

So, roughly speaking, an active male should consume between 60-100 grams of protein each day. That would be roughly equivalent to having: 

  • (1) Super Food Shake
  • (3-ounce) Chicken breast
  • (½ cup) Rice
  • (½ cup) Vegetables
  • (1) Banana
  • (1 cup) Greek yogurt
  • (2) Eggs  

INVIGOR8 Protein Shakes to Break Your Fast

Intermittent fasting isn’t so much a diet as it is an eating pattern where a person cycles between a longer fasting period and a shorter eating period. If done properly, it can support fat loss, muscle growth and cognitive performance. 

However, intermittent fasts aren’t a one-size-fits-all solution. For example, it could be dangerous for pregnant women and diabetics to engage in this eating pattern. Therefore, you should always consult with a professional before starting a new health plan. 

If you do receive the green light from your doctor or nutritionist, consider supplementing the eating windows with a high-quality protein supplement source like Inivigor8’s Super Food Shake, which was precisely formulated to build lean muscle, control hunger, reduce body fat, support immunity and promote overall health. 

To discover more about INVIGOR8, check out our weight loss kit and other appetite suppressant today. 


Healthline. Intermittent Fasting 101 — The Ultimate Beginner’s Guide.

Hopkins Medicine. Intermittent Fasting: What is it, and how does it work?

PubMed. Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting

The Healthy. Can You Drink Protein Shakes While Fasting?

MayoClinic. Are You Getting Too Much Protein?

About the Author

 Mara Welty
Mara Welty

Mara Welty is a copywriter who specializes in health, wellness and CBD topics. With a background in journalism, she aims to deliver engaging, research-based content that builds trust and engages readers through informative storytelling.

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