Does Whey Protein Break Intermittent Fasting?

Written by Andrew Brewer. ⚕️Reviewed and fact checked by our medical team.

Does whey protein break intermittent fasting

Protein is an essential building block for healthy muscles, and many fitness enthusiasts will integrate whey protein shakes into their diet when they’re looking to bulk up. Unfortunately, while it’s good for you, if you’re intermittent fasting, you want to skip the whey protein shakes during fasting windows. It will trigger an insulin response and break your fast.

Key Takeaways

  • Whey protein shakes should be avoided during intermittent fasting as they can trigger an insulin response and break the fast.
  • During the fasting window, stick to water, tea, and black coffee and avoid adding any sugar or sweeteners to your drinks.
  • Whey protein shakes can be consumed during the eating window to help hit daily protein goals, but it’s important to ensure they contain fiber and pair them with healthy fats.
  • Protein needs vary based on age, gender, weight, and activity level, so it’s best to consult a healthcare professional or registered dietitian to determine individual protein needs.
  • Following the rules of intermittent fasting strictly can help maximize the benefits, including kickstarting weight loss, increasing glucose tolerance, and healing the gut microbiome.

Why Can’t I Use Whey Protein While Intermittent Fasting?

During intermittent fasting windows, it’s not enough that you’re not eating any calories. You also have to avoid supplements that will prompt your body’s metabolic and insulin response. Either of these will break your fast, even if your caloric intake is zero.

Whey protein powder will do that when eaten alone or mixed with milk or water, so unfortunately, it will break your fast. During your intermittent fasting windows, stick to water, tea, and black coffee. Avoid adding any sugar or sweeteners to your drinks. Even zero-calorie sweeteners can trigger an insulin response in your body, which will break your fast. You will get the best results when you follow intermittent fasting rules strictly, so avoid the whey protein until your eating window.

If you do break your fast prematurely, you can delay some of the healthy benefits, including kickstarting weight loss, increasing glucose tolerance, and healing the gut microbiome. Even the smallest of responses can hinder your progress, so it’s best to stick to your eating schedule and avoid the whey protein until you’re ready to break your fast.

When To Drink Whey Protein Shakes

Just because whey protein shakes break your fast doesn’t mean you should cut them out entirely. On the contrary, these shakes are great ways to ensure you hit your daily protein goals, especially if you struggle with food alone.

One of the most common ways that you can break your fast is to drink a protein shake. This will be a gentle way to get your body ready to process food again. Check the nutritional label to see what’s in your whey protein powder. If you’re looking to break your fast, ensure it contains fiber in addition to other beneficial vitamins and minerals. For the best results, pair your shake with nuts. Healthy fats are essential to smoothly break your fast. Protein, fiber, and healthy fats are essential components of a balanced diet, and whey protein will help you with two of the three. Depending on what you mix it with, you may even be able to get the trifecta!

As you begin to plan how you’ll break your fast, start by calculating your daily protein needs. This is the minimum amount that you need to survive each day as you continue to build and maintain healthy muscles. You can eat more protein without little effect as long as you live an active lifestyle. Too much protein can hinder your progress if you lead a sedentary lifestyle.

You’ll get the most benefits out of your protein if you space it out throughout the day rather than loading a single meal with your day’s protein intake, so keep that in mind as you plan when to drink your whey protein shake. You can drink multiple shakes per day, just don’t use them as a complete supplement to eating. They contain many nutrients, but your body may not feel full, so you could end up eating more than you’d like.

Ultimately, whey protein is an excellent way to ensure you hit your goals, ensuring you’re nutritionally prepared for fasting. What you eat is just as important as when you eat, so make sure to eat lots of protein during your eating windows to help kickstart your metabolism.


  • Does consuming whey protein break an intermittent fast?

Consuming whey protein can break an intermittent fast as it contains calories and protein, which can cause an insulin response in the body.

  • How many calories does whey protein contain?

The number of calories in whey protein can vary depending on the brand and type, but on average, one scoop (30 grams) of whey protein powder contains around 120 calories.

  • Does consuming whey protein during an intermittent fast negate the benefits of fasting?

Consuming whey protein during an intermittent fast can negate some of the benefits of fasting, such as improved insulin sensitivity and autophagy.

  • Can I consume whey protein while still following an intermittent fasting schedule?

Consuming whey protein during an intermittent fasting schedule depends on the specific goals and reasons for fasting. Generally, it is best to stick to water and non-caloric beverages during fasting and save whey protein consumption for the eating window.

  • What can alternatives to whey protein be consumed during an intermittent fast?

Some alternatives to whey protein that can be consumed during an intermittent fast include plant-based protein powders, bone broth, and amino acid supplements.

  • How can I determine if consuming whey protein during intermittent fast suits me?

The decision to consume whey protein during an intermittent fast depends on individual goals, preferences, and health status. Therefore, it is always best to consult with a healthcare professional or registered dietitian before significantly changing your diet or fasting routine.

Andrew Brewer

Andrew Brewer

Andrew Brewer started to give people the guidance that he never received when he was first starting. His goal is to make your goals achievable and to offer you only the best fasting apps that the internet has to offer. You're not on your own - Andrew and the entire family of reviewers at are here with you every step of the way!