How to Build Muscle While Intermittent Fasting

There are many reasons why someone may follow an intermittent fasting diet, and why eating around the clock may not be suitable for them.

Although it is often viewed as a fat loss diet, many people adopt intermittent fasting as a full time lifestyle.

While it may not be the most ideal diet to build maximum amounts of muscle, there’s no reason why you can’t fully optimize your intermittent fasting diet to build as much as possible.

With the right structure and planning, there is a method to use intermittent fasting to build muscle.  

Using a 16/8 fasting to eating window, proper nutrient timing, and diversity in protein sources, you can build a considerable amount of muscle while intermittent fasting.

The following tips are to maximize muscle growth.  Can you go about intermittent fasting in a different way?  Of course, but this plan is the optimal approach to building lean muscle.

Follow a 16/8 Protocol

In order to build muscle you have to elevate muscle protein synthesis.  The body is constantly building up (synthesis) and breaking down (degradation) proteins simultaneously all day long.

Protein balance is often misunderstood.  It’s not as if you are switching back and forth between the protein buildup and protein breakdown, they are both going on at different rates at all times. 

To build muscle we want our rate of protein synthesis to exceed our rate of protein degradation as often as possible.

How do we do this?  Quite simply we have to consume adequate protein throughout the day, and the protein source we choose has to have sufficient Leucine. 

Leucine is the amino acid that stimulates protein synthesis.  As long as you’re eating quality sources of protein in sufficient amounts (chicken breast, eggs, whey protein, fish etc.), the Leucine content should be enough to spark muscle growth.

Even though Leucine is the main driver of protein synthesis, we still need all the essential amino acids to build new muscle.  You can’t just take a Leucine supplement and expect to build tons of muscle.  Taking Leucine on its own would be like having the light switch but no electricity.

Consuming quality sources of protein ensures that the body is getting the right amino acids to signal and build new muscle tissue.

Research shows the best meal frequency for maximum muscle protein synthesis is to have about four evenly spaced, high protein meals throughout the day. 

Due to our limited eating window we can’t achieve this, but we could still optimize it to the best of our abilities.  A 16 hour fasting window and 8 hour eating window would still allow for pretty good muscle growth potential.  Anything less than 8 hours would make it tough, but I’ve found that most people with physique-based goals who do intermittent fasting probably follow the 16/8 protocol anyway.

In an 8 hour eating window, you could easily fit in 3 high quality, evenly spaced meals (see meal plan below). Even 2 meals plus a shake would work if you want to keep the overall volume of food in the gut lower.

Nutrient Timing for Muscle Growth

There is a term called bodybuilding nihilism, coined by researcher and diet coach Menno Henselmans.

It refers to the attitude some people hold in the fitness industry that very few things really matter. Research has shown a lack of evidence for ideas like the post workout anabolic window, meal frequency for metabolism, food choices, etc.

Therefore in the minds of bodybuilding nihilists, this level of detailed thinking and planning is basically worthless. You can eat whatever, whenever, so long as you hit your macros.

In my opinion the pendulum with nutrient timing in particular has swung too far in this direction.  We’ve gone from slamming protein shakes immediately post workout to just eating when we get the chance. 

Just because the anabolic window is longer than we originally thought doesn’t mean it’s still not a good idea to time your nutrients in a certain manner.

In certain situations, like with intermittent fasting, nutrient timing becomes critical.  If you want to build as much muscle as possible, you simply can’t train fasted.  You need the right nutrients in the blood as you train. 

At the bare minimum, if you can’t eat beforehand, you HAVE to take an essential amino acid supplement if muscle building is your primary concern. 

Beyond that, you should consume an easy to digest meal of mainly protein and carbs immediately post workout.  A meal like this will digest and assimilate very quickly, as it lacks fat and fiber which slow the absorption rate of nutrients.

Using a Variety of Protein Sources

Nowadays too many people calculate their macros and follow them without any consideration for food choices.  Not all protein sources are the same.  Your primary concern should be with getting complete sources of protein which contain all of the essential amino acids needed to build muscle.

Essential amino acids cannot be synthesized by the body on its own and therefore must be consumed via diet.  This is typically not an issue as long as you’re eating meat, fish, eggs, dairy, or whey protein supplements. 

Vegans in particular usually have to combine foods in order to create a complete protein. Most vegan protein sources lack one or more essential amino acids.

However, there is more to choosing proteins than just making sure they are of a certain quality.  While complete protein sources contain all of the essential amino acids, they contain these amino acids in different amounts.  For example, beef is very high in the amino acid Lysine while chicken is high in the amino acid Arginine.  Therefore, it is critical to eat a variety of protein sources to ensure you’re getting adequate amounts of all amino acids to stimulate proper muscle growth.

A major mistake people make when tracking calories and macros is how they measure protein. Try this as an experiment: put a raw chicken breast on a food scale, cook it, then put it back on the food scale again.  The difference in weight can be quite staggering, about 2-4 oz. depending on its original size and how long you cook it for.

Why does this happen? Naturally any food will lose some size while cooking, but certain proteins like chicken are particularly problematic. Manufacturers often soak their chicken in a solution to make it larger and more plump. This is why you should measure meat after cooking.

Growth Hormone and Intermittent Fasting

Many advocates of intermittent fasting will laud the increases in growth hormone that can occur while in a fasted state as a major benefit of the diet. 

It’s important to note that these are endogenous increases; meaning they occur within the body itself.  These are not comparable to exogenous increases which occur when you inject it.  An endogenous increase in growth hormone likely will not provide any notable benefit.

In addition, growth hormone is not anabolic to muscle tissue in healthy individuals.

Yes, you read that right.

Growth hormone increases collagen synthesis and can stimulate cartilage growth, but will have no impact on skeletal muscle.  Even if it did, it wouldn’t matter.  Fasting is what stimulates the growth hormone production in the first place. 

While fasting, muscle protein synthesis is very low and there are not adequate nutrients in the system to build new muscle anyway.

So then why do so many athletes and bodybuilders take growth hormone?  Personally, I don’t think they know any better and are following performance enhancing drug dogma that has passed down for a few generations.  

As we mentioned it is very beneficial for cartilage and collagen health, which can aid in recovery from or prevention of injury (See Andy Pettitte).  It can also aid in lipolysis, which is the initial stage of the fat burning process.  But as far as actual skeletal muscle growth goes, it just doesn’t work.

Sample Meal Plan

Here is a basic outline of what an optimal, muscle building, intermittent fasting diet would look like.  You will see the timing and the food choices but not the amounts, since it would be silly to do so.  A 100 lb woman and a 260 lb man following an intermittent fasting diet require radically different amounts of food.

For simplicity let’s say your feeding window was from 12pm – 8pm.  Obviously you can adjust the times based on how you do it personally.

Meal 1: 12pm

Eggs, Oatmeal, and Berries

This is a very balanced meal.  The fat from the eggs and fiber from the oats and berries will allow nutrients to slowly release into the blood for the next few hours, timing perfectly with our workout to come. Eggs are also one of the most bioavailable sources of protein.

Workout: 2pm (Essential Amino Acids Optional)

By now meal one should clear the stomach and nutrients are flowing through your system toward the working muscles.  Since two hours have passed since meal one you should feel satisfied but not slow or sluggish.  This allows for optimal workout performance while providing the raw materials for muscle growth.

Having a meal in your system ensures that your body isn’t in a crazy catabolic state from the workout.  Every workout will cause catabolism to some degree, but oftentimes it creates a hole too deep for one to adequate climb out of (especially on an intermittent fasting diet).

Meal 2:  4pm

Chicken and Rice

This meal lacks fat or fiber which means it will digest very quickly and jump start the recovery process.  Again, say what you will about the post workout anabolic window, but that doesn’t mean nutrient timing isn’t important (especially in certain situations).

Meal 3:  7:30pm

Steak, Potatoes, and Broccoli

Concluding the day with another well-rounded meal.  Similar to meal one, the fat from the steak and fiber from the broccoli will result in sustained release of nutrients into the blood.  This is a nice, satiating meal to finish your day.  Also take note of the protein source; we’ve now consumed three different meals evenly spaced out with three different, high quality protein sources.  By the time you finish this meal it will be about 8:00pm and your fasting window will begin.

Again, it’s important to note that there tons of different routes to intermittent fasting.  Just because you don’t follow this framework doesn’t mean you won’t find success.  But with this system of food choices and nutrient timing, I feel this is the optimal diet and training structure to build as much muscle as possible while intermittent fasting.