As a certified personal trainer and nutritionist, I often get asked, "does a protein shake break a fast," and I totally get why.

The intermittent fast has been growing in popularity as a weight loss and health-promoting strategy, while protein shakes are a staple in many people's diets.

So, it's only natural to be wondering if these two things can coexist.

Let me cut to the chase: it depends on your fitness goals (or fat loss) with intermittent fasting and what kind of protein powder you're consuming. (I know that's not the definitive answer you hoped for, but stick with me here.)

The short answer is yes, but it’s better if you understand why.

There are different types of fasting, and generally, every fasting involves refraining from food and drink for a specific period of time.

Many such eating patterns have appeared during the last decade, while fasting has been known for religious purposes for thousands of years.

Our focus today is intermittent fasting, not-so-new-concept, but before we dive into the nitty-gritty details, let's first understand what it is.

Intermittent fasting is an eating pattern where it is necessary to eat only during a certain window during the day and fast the rest of the day. Outside the eating window, you can only drink water, unsweetened black coffee, and tea.

Many studies speak in favor of starting intermittent fasting, not only for achieving fitness results but also for overall health.[1]

Perhaps the biggest advantage of it, in my opinion, is long-term sustainability.

Each restrictive diet can last only for a certain time, while you can follow IF for years in a convenient way.

You can adjust it to your schedule and goals, so you can use the most effective ways - the 16:8 method, 14:10 method, 5:2 (non-consecutive days), or try other forms. Even longer fasting is possible but is not suitable for every metabolism.

And now the answer to the main question can you drink protein shakes while intermittent fasting?

So yes, protein shakes break your fast.

Remember I said at the beginning that it depends? That is still true.

Protein intake breaks a fast because protein shakes contain calories and amino acids will cause an insulin levels spike, so technically, the fasting period stops. However, it doesn't have to be so important.

For example, if you're doing intermittent fasting for autophagy, then consuming protein shakes during your fast would stop that process since insulin response inhibits autophagy. And amino acids have the capacity to stimulate secretion of it.[2]

On the other hand, if you're doing it for weight loss or blood sugar regulation, a protein shake might not be a dealbreaker.

In fact, it could actually help you stay in a caloric deficit. Protein is known to promote feelings of fullness, and more protein can help stabilize blood sugar levels, both of which help keep body mass stable.

Of course, we should not forget that's the best way to build muscle and speed up muscle recovery.

Empty Plate With Utensils

How To Take Protein Shake While Intermittent Fasting?

If you belong to a group of people for whom the triggering of autophagy is not the primary target, the following tips can help you to fit a protein shake and other essential amino acids (building blocks) into your daily intermittent fasting plan and eating windows.

Don’t forget that time-restricted eating requires more dedication for planning meals, or you can be in a significant calorie deficit. Skipping breakfast, for example, can make it hard for you to meet protein requirements.

Choose A Protein Shake That Is Low In Calories And Carbohydrates

Not all protein shakes are created equal, so you must check the ingredient list. Many protein powders contain added sugars, artificial ingredients, and other additives that could break your fast or have negative health effects, even though they claim to be great for weight loss.

Honestly speaking, US supplement manufacturers tend to add more sugar, artificial sweeteners, flavors, and colors to protein shakes than European manufacturers.

I'm not saying it's always the case; I certainly haven't tried every single protein on these two markets.

Still, I could conclude this after consuming protein supplements for almost a decade. Frankly, US protein powders taste better almost always, and I lean towards them usually.

In the case of intermittent fasting, more carbs and more calories are not what you want. Even if autophagy isn't your primary concern, you don't want to ingest 10 or 15 grams of sugar and raise your calorie intake significantly.

So, it's essential to choose a high-quality protein powder with minimal ingredients and no added sugars (it doesn’t have to be zero sugar) for your eating window.

Remember, you have to mix your protein powder with some liquid. Even though almond milk and other plant-based milk have less protein than regular milk, they also have almost no sugar. So, my advice is to mix your protein with low-calorie milk replacements or plain water, especially during fasting windows.

Time Your Protein Shake Consumption Appropriately

Let's say you have just started with intermittent fasting and consume food during the 10-hour window (14:10 method.)

In those ten hours or ideally eight hours, the average person should eat at least two meals and have one or two healthy snacks for muscle building or if you are trying to lose weight.

You can opt for three meals with fewer or no snacks. Time your protein shake consumption so that it has the most benefits during the eating period.

Whether you are drinking it earlier in the day or the evening, find a gap between meals during the eating window when around 20 grams of protein, which is an average scoop size, will be an excellent way to boost your protein intake even more.

Consider Consuming A Protein Shake After Your Workout

Once, the anabolic window was considered an almost magical span when protein consumption leads to incredible muscle growth.

Today we know that the anabolic window is almost irrelevant to everyone except professional bodybuilders.[3]

However, that doesn't mean it's a bad idea to drink protein shakes right after your workout.

Since I believe that you should not work out on an empty stomach, not even for a morning workout, then this implies that you will go to the gym during the feeding window and that you can drink protein shakes afterward to build lean muscle mass, but not as a meal replacement.

Be Aware Of The Potential Risks

Protein powder is one of the safest supplements for healthy adults, whose side effects are limited to bloating and similar digestive problems, especially in people who are lactose intolerant. Those with kidney problems should exercise caution.[4]

Also, you must be aware of the potential risk of breaking your fast. Any amount over 50 to 100 calories during the fasting window will get you out of the fasting state.

Is Protein Important For The Cutting Phase?

Protein is equally important during the cutting phase and bulking. We could discuss how much protein you need during which period, but one thing is certain - it is a critical molecule for our bodies.

When you want to lose weight, focus your diet regime on proteins, fiber, and healthy fats. If, in general, your overall protein intake is 1.5 grams of protein per lb of body weight.

During cutting, you can increase protein intake to over 2 grams per lb of body weight. While bulking, you need more carbohydrates but still plenty of proteins and fat to grow muscle mass.

That's why protein shakes should be part of your daily routine all year long.

Intermittent fasting is no different - you need enough protein from protein-rich foods and to drink whey protein. It will not prevent you from experiencing a single benefit and will actually help you take most of IF.[5]

Adding A Scoop Of MyProtein Impact Whey Protein To Water

Intermittent Fasting and Protein Shakes Questions

Should you have a protein shake after fasting?

You can have a whey protein powder after the fasting period, but the body will also need fats and carbs after such a long period without food. So, don't limit yourself to a protein shake; combine it with a complete meal or take it as a snack.

Can you drink protein water while intermittent fasting?

It depends on the ingredients of protein water you are about to consume. If the only ingredients are protein isolate and water, in most cases, you can consume it and still maintain a fasting state.

Should I consume protein shakes before or after my fasted workout?

There is no significant difference in timing; the daily protein amount is what you need to satisfy rather than time. Evaluate whether you need to drink protein shakes before to feel fuller or after to regain energy, even though protein is not an energy source.

What is considered a "Fasting State"?

You enter the "fasting state" when you stop eating completely for at least 10 hours. Then the glycogen stores in the liver are significantly depleted, and the body begins to use the reserves of fats and proteins. The next time you eat and consume calories, you will break your fast.

So, Can You Take Protein Shakes While Fasting?

As with most things in nutrition, the answer isn't black and white. It varies based on your ambitions and the specific protein shake.

So, whether you skip the protein shake during your fasting hours or enjoy protein drinks as part of your eating window, remember there's no one universal approach. Instead, experiment with what works best for you, and be bold and ask questions or seek guidance from a registered dietitian.

And as always, make sure you're fueling your body with whole, nutrient-dense foods that support your health and well-being. Because at the end of the day, that's what truly matters, even more than reaping the benefits of intermittent fasting.

Thanks for reading, and happy fasting!


Miloš Lepotic

Miloš Lepotic

Miloš loves three things - science, sports, and simplicity. So, what do you get when you put the three together? A no-BS guy that's all about efficient workouts and research-backed supplements. But he also thinks LeBron's the greatest ever, so...