Anabolic Fasting: Here’s How it Works

Whether you’re a bodybuilder, powerlifter, or competitive athlete, you already know that just about the last thing you want to happen when you’re trying to shed some unwanted body fat is to see some of your precious lean muscle mass go to the wayside as well.

The unfortunate reality though, is that this is exactly what tends to happen with most traditional low-calorie weight-loss diets.    Sure you’ll lose some body fat, but you’ll also potentially lose significant amounts of muscle if all you do is cut your calories drastically.  

However, anabolic fasting is a dieting principle that seeks not only to help you burn more body fat but also to preserve -- and even build -- muscle mass during a weight cut.  

But from understanding how to go about setting up your fast to figuring out how exactly to manipulate your macronutrient intakes, there are a few things you’ll need to get right in order to have success with anabolic fasting. 

What is Anabolic Fasting?

The anabolic diet is an eating protocol originally pioneered by Dr. Mauro DiPasquale, a former world champion powerlifter and assistant professor at the University of Toronto.  Its initial aim was to provide the body with the right nutrients to support muscle growth and recovery, while at the same time minimizing its fat stores.  

In more recent years, it’s been further refined and popularized by Cory Gregory (supplement company owner and fitness expert) into a fine-tuned eating strategy used by the likes of many different strength and fitness athletes looking to get bigger and leaner.    

In its essence, anabolic fasting is an eating protocol that cycles between fat burning and muscle-building stages.  It does this primarily by altering your carbohydrate intake.  

On some days you’ll be eating a very low number of cabs, replacing them with more healthy fats and protein in your diet.  On other days, you’ll focus on replenishing your glycogen stores and consume a large number of carbs, while cutting back on your fat intake.  

“​​According to DiPasquale, alternating carbohydrate intake allows you to burn more fat as fuel. This allows you to preserve as much muscle mass as possible.”

On top of cycling between high-carb and low-carb days, as you might expect from the name, you’ll also be following a fasting protocol with anabolic fasting.  That means you’ll have a relatively small window each day, where you’ll consume all your calories, and then the rest of the day you’ll consume only water.  

One of the perks of anabolic fasting is that it doesn’t place any kind of restrictions on your daily calorie intake (like most fat loss diets), so you’re free to eat as much as you want within your eating window (assuming you’re eating the right foods).   

Is Anabolic Fasting Supported By Science?

While there hasn’t been any direct research on anabolic fasting itself, a number of trials involving intermittent fasting and carb cycling -- the 2 main parts of the overall eating strategy -- have demonstrated positive findings.     

For example, numerous weight-loss studies involving intermittent fasting have shown that it can lead to similar amounts of weight loss compared to traditional calorie-restricted diets.^(1)(2)(3)

However, what makes it particularly attractive when it comes to building muscle, is that research has also demonstrated, time and again, that intermittent fasting helps to preserve more lean muscle mass and burn up more fat compared to traditional weight-loss diets.⁽⁴⁾⁽⁵⁾

So while you might lose similar amounts of weight with both eating strategies, you’ll ultimately be in a much better position to make significant improvements to your overall body composition with intermittent fasting.  

When it comes to carb cycling, not quite as much research has been conducted when compared to intermittent fasting.  However, with that being said, several studies have demonstrated positive results both when it comes to improving your workout performance and overall appearance.  

For instance, one 2008 study ultimately showed that several days of a high-carb intake prior to athletic competition helped to increase muscle glycogen stores and significantly improve performance in athletes.⁽⁶⁾  Other research involving professional bodybuilders also found that carb-loading prior to competition helped to increase overall muscle volume and physical appearance.⁽⁷⁾

How Does Anabolic Fasting Work Exactly?

With the intermittent fasting aspect of the diet, you’ll be operating within an 8-hour window in which you’ll be consuming all of your daily calories; the other 16 hours of the day you’ll be calorie-free.  

Remember, sleep will take up as much as half your time fasting, so it’s not quite as bad as it may first seem.  12 pm - 8 pm is probably the most popular time frame, however, you can set up your eating window in whatever way best suits you.   

With the carb cycling component of the anabolic fasting, you’ll be cycling between low-carb and high-carb days throughout each week.  For 5 days straight, you’ll be consuming just about no carbs (as little 25g or less), and then for the following 2 days, you’ll flip things around and get most of your calories from health carbohydrate sources.   

Most people chose to have their low-carb days fall on the weekdays and their high-carb days on the weekends, however, you can set up your schedule how every you’d like.  On low-carb days(Monday - Friday), the goal is to get around 65% of your total daily calories from healthy fat sources, 35% from protein, and only about 5% from carbohydrates.  

On high-carb days (Saturday and Sunday), on the other hand, the goal is for 60% of your total daily calories to come from carbs, with only 15% coming from protein and 25% from healthy fats.  

It’s important to point out though that before you get started on the normal 5/2 cycle, the protocol recommends that you spend 12 days consuming no carbs in your diet in order to get your body properly adjusted to using fat and not carbs as its primary energy source.  After that, there are 2 high-carb days to replenish your glycogen stores and then you jump into the normal weekly cycle.  

What Foods Can You Eat While Anabolic Fasting?

Not only is it important to get your macronutrient ratios right while anabolic fasting, but you’ll also need to be getting your calories and macros from nutritious food sources.  

That means keeping highly processed foods to a minimum and favoring nutritious, whole foods like fresh meats, minimally processed cheeses, and certain nuts and oils, along with things like whole grains, fruits, and vegetables on high-carb days.  Here are lists of several different healthy food options for each macronutrient: 

Healthy Sources of Protein

• Lean Meats
• Fish
• Eggs
• Protein Powder Supplements

Healthy Sources of Fat

• Olive Oil
• Yogurt
• Cheese
• Nuts
• Fish

Healthy Sources of Carbohydrates

• Vegetables
• Fruits
• Brown Rice
• Whole-Grain Pasta
• Whole Wheat Bread
• Minimally Processed Oatmeal

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What are the Risks and Downsides?

While there are plenty of benefits to be had from anabolic fasting, it’s not an eating protocol to follow indefinitely.  It’s primarily due to the fact that eliminating things like vegetables and fruits from your diet 5 days out of the week can deprive your body of important micronutrients over time.  

Ultimately that’s why many bodybuilders and powerlifters cycle between bulking and cutting phases, where they spend a few months packing on as much muscle mass as possible (and replenishing their nutrients) and then shift over to anabolic fasting for the next couple of months, where the focus becomes cutting away unwanted body fat while holding on to size and strength gains. 

Wrap Up

Anabolic fasting is a dieting protocol that’s become popular amongst people like bodybuilders, powerlifters, as well as certain competitive athletes.  In essence, it combines the eating strategies of intermittent fasting and carb cycling into a fine-tuned plan that targets your body’s fat stores and preserves your lean muscle mass.  

Anabolic fasting alternates between low-carb and high-carb days, where you’ll spend 5 days eating next to no carbs and then the next 2 days eating lots of carbs, repeating the cycle from week to week.  All of the while you’ll also be fasting, eating all of your calories within an 8 hour time window each day.  

When it comes to selecting the right foods to eat (and to avoid), the best bet is to avoid highly processed foods and to go with fresh, nutritionally dense foods like meats, fish, yogurt, cheese, nuts, olive oil, and whole-grain pasta and bread on high-carb days.  

• References
  1. “Effect of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk: A randomized 1-year trial”Sundfor, T.M., et al. Nutrition, Metabolism and Cardiovascular Disease. Jul. 2018.
  2. “Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials”Seimon, R.V., et al. Molecular and Cellular Endocrinology. Dec. 2015.
  3. “Intermittent energy restriction and weight loss: a systematic review”Davis, C.S., European Journal of Clinical Nutrition. Mar. 2016.
  4. “Intermittent Fasting: Is the Wait Worth the Weight?”Stockman, M-C., et al. Obesity Treatment. Apr. 2018.
  5. “Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?”Varady, K.A. Obesity Reviews. Mar. 2011.
  6. “The latest on carbohydrate loading: a practical approach”Sedlock, D.A. Current Sports Medicine Reports. Aug. 2008.
  7. “Carbohydrate Loading Practice in Bodybuilders: Effects on Muscle Thickness, Photo Silhouette Scores, Mood States and Gastrointestinal Symptoms”de Moraes, W.M.A., et al. Journal of Sports Science and Medicine. Nov. 2019.