What Is Protein Fasting? The Surprising Benefits of Protein Cycling
- Protein fasting is an easy, flexible eating style that offers health benefits and can help support your overall wellness goals.
- Also known as protein cycling, protein fasting involves limiting your protein intake to fewer than 15 grams, once per week.
- Read on to learn all about the benefits of protein fasting, how it works and how to incorporate it into your own lifestyle.
Protein fasting is one of the most powerful, but underutilized tools in your toolkit for peak performance.
Also called protein cycling, protein fasting can help manage inflammation, kick-start fat loss and help you stay on your A-game. One day per week, you limit your protein to 15 grams or less per day. Throughout the day, eat quality fats, moderate carbs and near-zero protein. Easy, right?
Protein fasting might sound extreme if you’re trying to maintain muscle mass or hit specific macronutrient goals. The good news is that there are some real benefits and science behind occasionally cutting back on your protein intake.
What is protein fasting?
Eating lots of high-quality protein is a good thing—but so is taking a day off from protein.
By protein fasting once a week, you’re essentially allowing your body a full day to use its digestive machinery to perform self-maintenance. This process is called autophagy—or, literally translated, self-digestion.
Over time, cells accumulate dead organelles, damaged proteins and oxidized particles that interfere with cell function and accelerate aging. Autophagy is the body’s natural cleaning process. It recycles the junk in your cells, turns it into energy and uses it to help build new proteins and membranes.
Cleaning out the clutter helps keep you young. Here’s how periodic protein cycling supports this natural detox process.
Protein fasting ramps up “cleanup mode” in your cells
The main way to induce autophagy is through fasting.[1] You can also induce it by dramatically lowering your protein intake once a week.[2]
Essentially, autophagy is like a trash incinerator for your cells, and protein fasting turns up the heat.
When you occasionally limit protein consumption, you force your cells to find every possible way to recycle proteins. In their search, they bind and excrete toxins that were lurking in your cell’s cytoplasm, the gel-like substance enclosed within the cell membrane.[3]
It’s like taking your car to the car wash and having it deep cleaned.
Is it okay for everyone to have a low-protein day?
Like intermittent fasting, protein fasting is not an all-or-nothing deal. Play around with this style of protein diet to find what works for you.
This may not be for everyone, especially if you’re pregnant or taking certain medications (so talk to your doctor before you try it). Also, fasting of any kind can be stressful for the body, so protein fasting might not be a great choice if you’re currently dealing with a lot on your plate.
You can adjust the total amount of protein you’re eating on the day of your protein fast. You might feel fine with virtually zero grams of protein, or you might need the full 15 grams. This is another great opportunity to experiment in order to get optimal results.
Does protein fasting interfere with muscle mass?
You may be concerned about muscle catabolism, which is when your body gets its protein requirements from your skeletal muscles. Understandable—you don’t want to negate all of your progress at the gym.
Fortunately, protein fasting doesn’t interfere with muscle building. In fact, this dietary method can benefit your muscles because autophagy is required to maintain muscle mass.[4]
If you’re interested in staying younger, bodybuilding and maintaining a healthy body weight by spending less time working out (and who isn’t?), it makes sense to trigger autophagy.
Studies have also shown that protein deficiency lowers insulin levels and mTOR.[5][6] That’s good news for muscle gains: One of the keys to building muscle is stomping down mTOR so its secretion can spring back up.
Here are two key considerations:
- You only want to become temporarily protein deficient. Chronically under-eating protein is awful for your brain and your body. The magic number varies depending upon your activity level and own biology, but you can start by aiming for 15 grams of protein once per week. The rest of the week, stick with your regular diet.
- Avoid going for PRs protein fasting days. Don’t try to build muscle on a day that you aren’t taking in protein. Save your protein fast for lighter-activity days. If you want to exercise, stick with gentle movements, like walking or mobility work.
Related: How to Find Your Ideal Protein Intake
Why protein fasting isn’t super intuitive
It turns out you might think you are protein fasting if you aren’t. Here are a few potential reasons why:
- You’re eating foods you don’t realize contain protein because we don’t think of them as typical high-protein sources. Of course, it’s intuitive that protein shakes are loaded with protein. But did you know that broccoli has a little protein in it?
- You aren’t accounting for serving size. By law, the government allows companies to label anything with less than one gram of protein per serving as having zero grams. If you eat more than the recommended serving size, you might inadvertently eat a few grams of protein.
- You aren’t sure what a protein-free day of eating might look like or how to count/measure in grams. (Read below for easy solutions with Bulletproof Protein Fasting.)
How to succeed with your protein fast
Remember, your goal is to stay below 15 grams of protein total during your one protein fasting day each week. Some people find it hard to keep track of their overall caloric intake and protein intake, so here are some tips:
More Diet Tips From Bulletproof
1. Track it
If you want to eat something and you aren’t sure if it has protein in it, consider downloading a food tracker app on your phone. These handy calculators take all the guesswork out of how much protein and other macronutrients are in your food.
More Diet Tips From Bulletproof
2. Buy a digital kitchen scale
By purchasing a small kitchen scale, you’ll be able to measure out your portions quickly and easily—which is useful for plenty of recipes, whether it’s protein fasting day or not.
3. Refeed on high-quality carbs
Keep in mind that this is not a cheat day. Do not give yourself permission to hit up all of your local fast-food joints and then eat an entire cake. Protein fasting is simply a great way to help reduce inflammation and feel your best.
Heads up: Protein is the most satiating macronutrient, so you might not feel as satiated during your first few attempts at a protein cycling in comparison to other days of the week. Set yourself up for success by reaching for high-quality, nutrient-dense whole foods, and give yourself permission to eat more often during a protein fast.
Not sure what protein cycling looks like? Check out our Bulletproof Protein Fasting sample meal plan below.
Bulletproof Protein Fasting sample meal plan
The Bulletproof Diet is a cyclical keto style of eating that prioritizes anti-inflammatory foods and behaviors—including protein fasting. About one to two times a week, you limit your protein intake to 15 grams to support autophagy.
To keep you full and energized, start your day with a cup of Bulletproof Coffee. Have high fats and moderate carbs throughout the day, and save your carbohydrate intake for the afternoon or evening.
Here’s a sample shopping list to stock up on in preparation for your big day of protein fasting:
- Quality fats like grass-fed butter, Bulletproof Grass-Fed Ghee, olive oil and coconut oil
- Sweet potatoes, yams, carrots, cucumber, celery
- Avocados
- White rice
- Low-fructose fruits, like berries
- Bulletproof Coffee ingredients: Bulletproof Brain Octane C8 MCT oil, Bulletproof coffee beans and grass-fed butter or ghee
The following sample meals will help your body detox even more efficiently while giving you an extra boost of energy.
1. Bulletproof Protein Fast Breakfast
Choose one to have as soon as you get up, or whenever you’re accustomed to eating breakfast.
- Bulletproof Coffee (without any added protein)
- Green tea blended with butter and Brain Octane C8 MCT Oil
Bulletproof tip: Try this Vanilla Matcha Latte recipe, but hold the collagen protein during your protein fast!
2. Bulletproof Protein Fast Lunch
Choose one to be eaten 15 to 18 hours after last night’s dinner.
- Bulletproof Guacamole with cucumber and/or celery sticks
- Cleansing Ginger Carrot Soup made without bone broth
- Bulletproof Veggie Buddha Bowl without eggs
3. Bulletproof Protein Fast Dinner
Choose one to be eaten 5 to 6 hours after lunch.
4. Bulletproof Protein Fast Dessert
If you like to end your day with something sweet, enjoy this dessert soon after dinner.
- Bulletproof Berry Bowl: Combine blueberries, raspberries and strawberries with a squeeze of lemon juice and a sprinkling of fresh chopped basil
The meal ideas above are just a quick sampling of the types of foods you can eat while protein fasting. Find more recipes ideas on the Bulletproof Recipes page.
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This article has been updated with new content.