Intermittent Fasting Bodybuilding: What You Thought You Knew Is Wrong

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Intermittent Fasting Bodybuilding: What You Thought You Knew Is Wrong


There are many people in the fitness community who think that intermittent fasting bodybuilding isn’t possible. While some believe that fasting will put your body in starvation mode and reduce muscle mass, others suggest that eating multiple small meals throughout the day is the key to an efficient metabolism.


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But research is challenging this belief. As it turns out, intermittent fasting (IF) may be the key to boosting your performance in the gym and seeing keto gains a lot faster.

What Is Intermittent Fasting?

Intermittent fasting is a diet pattern that cycles between eating windows and fasting windows. These windows vary per person, and different methods work for different goals, as you’ll learn below.

Which Intermittent Fasting Method Is Best?

Intermittent Fasting Bodybuilding: types of intermittent fasting

There is no right or wrong method for intermittent fasting. You have to find a pattern that works for you, your goals, and your schedule.

Here are the four most popular types of intermittent fasting.

Method #1: Skipping meals

If you’re new to intermittent fasting, the most comfortable point of entry is to skip meals.

For example, If you have a large dinner, forgo breakfast and choose lunch as your first meal of the day. If you’re not hungry at dinnertime, skip it and resume eating at breakfast.

This is the easiest way to get into the rhythm of fasting, but longer approaches provide more metabolic and cognitive benefits.

Method #2: Fasting daily during a specific time window

The most common approach to intermittent fasting is dividing your eating and feeding windows by hours.

A popular way to do it is the 8/16 method, where you eat within an 8-hour window each day (for example, 10 a.m. to 6 p.m.), and then fast for 16 hours.

You can stretch your fasting window as you become more comfortable with IF, and eventually get to an 18/6 or 20/4 approach.

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Method #3: Alternate-day fasting  

A more advanced approach to fasting involves not eating for 24-36 hours several times per week.

The most common method is to fast for 24 hours, eat normally for 24 hours, and then returning to another full-day fast.

2 Misconceptions About Intermittent Fasting for Muscle Growth

There are several myths about the effects of intermittent fasting on muscle growth and breakdown. Here are the two most common misconceptions.

Myth #1: Fasting Makes Your Body Break Down Muscle

Protein is not your body’s preferred energy source.

Your body will always use glucose (which you consume through carbohydrates and sugar) first. Glycogen, or stored glucose, is second. After your body uses up these two, you start burning fatty acids (transformed into ketone bodies in the liver).

On a carb-based diet, you can fast for a full 24 hours before losing your glycogen stores. During this time, protein is not affected. It could take two days — a full 48-hour fast — to potentially cause a loss of muscle mass.

If you’re doing keto, intermittent fasting boosts your ketone levels, so you have more energy, and it spares your muscles.

Either way, intermittent fasting won’t make you lose muscle.

Myth #2: Intermittent Fasting Is Starvation

Intermittent fasting is not the same as prolonged fasting, which is an extended period of calorie restriction.

Extended fasting should only be used for specific health and therapeutic purposes. Misused, it can lead to hormonal problems, muscle loss, weakened immunity, and a slower metabolism[*][*].

Intermittent fasting is also different from starvation. Starving yourself for several days without the supervision of your trusted health physician can lead to a host of health problems.

Intermittent fasting, on the other hand, provides numerous health benefits, including:

  • Weight Loss: Research shows intermittent fasting is an efficient fat loss tool, even better than simply cutting calories. One systematic review and meta-analysis found intermittent fasting is just as effective as continuous calorie restriction for short-term weight loss[*].
  • Disease Prevention: Intermittent fasting can help improve your risk of multiple diseases, boost your immunity, and increase longevity[*]. In one study, IF helped improve cardiovascular risk and slow the progression of type 2 diabetes[*].
  • Improved Insulin Sensitivity: While fasting, your glucose and insulin levels get normalized, which helps you become insulin sensitive[*].
  • Preserves Muscle Mass: Research shows intermittent fasting can preserve muscle, not break it down. In one 4-week study, researchers concluded a fasting diet resulted in more significant weight loss — while maintaining muscle mass — than participants following a low-calorie diet. This happened even though the total calorie intake was similar in both groups[*]

Intermittent fasting isn’t the same as prolonged fasting or starving. Research finds it has metabolic and muscle-sparing benefits greater than simply cutting calories.

How To Use Intermittent Fasting For Bodybuilding

Because intermittent fasting has multiple health benefits and helps preserve muscle mass, you can use it to reach your fitness goals, improve your athletic performance, and lose fat.


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#1: Be Strategic With Fasting

It’s best to pair your fasted days with your rest days. For example, if you schedule active recovery on Wednesdays and your off day on Sunday, those should be your fasted days. Save your workouts for days where you eat normally.

Research shows some people may struggle during their weight training and cardio sessions when fasting[*].

#2: Use Intermittent Fasting to Halt Your Cheat Days

Some people worry intermittent fasting will only cause a series of binges and cheat meals. But research shows IF can help suppress your appetite.

In one study, participants who tried intermittent fasting displayed fewer signs of emotional eating. Participants claimed they were less hungry, more satisfied, and significantly less prone to indulge on their “cheat days”[*].

#3: Eat Roughly the Same Amount of Calories and Macros

If you’re following the 16/8 method, you shouldn’t restrict calories too much during your feeding window. Aim to eat almost the same amount of calories, only within a shorter feeding window. Eating at an excessive calorie deficit may compromise your muscle gains at the gym[*].

On top of following these tips, you can boost the effectiveness of intermittent fasting for your workouts by taking the right supplements.

Top 3 Supplements for Intermittent Fasting Bodybuilding

As a bodybuilder, especially if you’re doing keto, taking a few key supplements can help you preserve muscle mass, prevent fatigue, and make intermittent fasting easier on your body.

#1: Exogenous Ketones

When you fast, your body first burns your glucose stores and then turns to fat for energy. This fat then converts to energy molecules called ketones.

Using mainly ketones for energy is called ketosis, and it’s what makes fasting possible. Without ketone bodies, you wouldn’t be able to survive very long without food.

To increase your energy levels while fasting — and therefore not sacrifice your performance at the gym — you can boost the ketones floating in your blood by supplementing with exogenous ketones.

Exogenous ketones are supplemental ketone bodies that boost your blood ketone levels and therefore give you more available energy.

#2: Collagen Protein

You probably know that eating enough protein is vital for building muscle and increasing your performance.

Collagen is a type of protein that provides essential amino acids for your muscles, heart, joints, brain, and other vital organs. You need collagen to build up almost every single tissue in your body[*][*].

Taking collagen while fasting helps provide some of the essential nutrients you need to make gains.

When looking for a collagen supplement, make sure it doesn’t have sweeteners or fillers that could spike your blood sugar or harm your health.

Perfect Keto collagen is a clean, keto-friendly protein from grass-fed cows that provides 10 grams of protein per scoop, and just 1 gram of carbohydrates.

Pro tip: Take collagen before you work out, not only after. Research shows taking collagen before a workout can increase its absorption in your joints.

#3: A Clean Pre-Workout

What you eat before your workout matters, so you have to choose wisely.

Drinking a pre-workout shake filled with sweeteners that raise your blood glucose can cancel some of the benefits of fasting.

Ideally, you want your pre-workout fuel to be nourishing and free of potentially harmful, unnecessary ingredients.

Perfect Keto Perform was created for athletes and casual gym-goers alike who follow a keto diet. It contains BHB (the primary ketone used for energy), MCTs (for sustained energy), BCAAs (to promote muscle performance), creatine (to support muscle gain), and L-citrulline (to delay muscle fatigue).

Whichever pre-workout you choose, make sure it supports your goals instead of hindering them.

You Can Do Intermittent Fasting and Build Muscle

Contrary to popular belief, intermittent fasting can be a great tool for bodybuilding.

Intermittent fasting bodybuilding helps to accelerate fat loss, preserve muscle mass, improve your overall health, and boost longevity.

If you decide to test the benefits of IF while building muscle, try to pair your fasting days with your rest days and make sure you’re not restricting your calories too much.

There are several supplements you can take to make intermittent fasting easier while you do keto and build muscle. Consider taking exogenous ketones, keto-friendly protein, and a high-quality pre-workout, all of which will help prevent fatigue, boost your energy levels, keep your training effective, and, of course, help you get those gains.


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6 thoughts on “Intermittent Fasting Bodybuilding: What You Thought You Knew Is Wrong

  1. Ive read and practice drinking coffee in the morning with coconut oil and grassfed butter as part of an intermittent fast (dinner to 2pm the following day). I wasnt sure how the practice technically qualified as ok for consuming during intermittent fasting time other than because there’s no carbs so there’s no subsequent spike in blood sugar. Does this philosophy “technically speaking” align with intermittent fasting?

  2. I’m not a bodybuilder. I’m a powerlifter. So looking muscular is not my ultimate goal, strength is my goal. I have been doing keto for 3 months now. I’ve dropped over 50lbs which is great. However I have lost a substantial amount of strength. Almost nothing I’ve read talks about increasing strength performance. Please address this in further post. I have added more protein into my diet to help and considering adding a carb drink after my lifts to help. Is there a better “keto” way. My ratio is still higher fat 56-35-9 (fat-protein-carbs)

  3. This article is poorly informed and has many errors. Let’s start with the fact that collagen is useless for building muscle. It’s utility lies in improving the structure of skin, hair, nails, bone, ligaments and so on. It contains insufficient amounts of BCAAs to be useful for building muscle and should be used additively rather than substitutively to a bodybuilding diet.
    Second, for the maintenance or enhancement of lean body mass, it is better to eat slightly less protein on weight training days and slightly more on rest days. Why? Because when training, there’s already an anabolic stimulus owing to the training which will make the utilisation of amino acids by muscle tissue more effective. On rest days, there’s no training as an anabolic stimulus, so dietary protein is the only anabolic stimulus and is needed in greater quantities to maximize muscle protein synthesis then when combined with training.
    I can’t remember off the top of my head what other errors or in your article, and I’m not prepared to re-read it, as I’ve read a lot of your articles and they are full of assertions which are not supported by science. It is not education but marketing. You’re not an expert but a salesperson.

    1. Hi Aaron, you may be correct in saying that collagen protein does not stimulate muscle protein synthesis but it does still play a role in the structure and function of muscle.

      Also as you mention the anabolic stimulus from training, it is important to note that studies that show what you are saying is in untrained populations. This same response to training is not found to the degree you are saying in more trained populations. This makes the need for protein different from person to person.

      I hope I was able to clarify this for you.

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