The Truth about Intermittent Fasting Muscle Gain

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Last updated on September 5, 2022

Intermittent fasting is quickly gaining popularity and each individual has a different reason for taking up the program. Most people get into intermittent fasting for weight loss as it helps in reducing the number of calories that one takes in.

Others fast for religious reasons, such as Islam, requires its faithful to fast every Ramadhan, and isn’t necessarily connected to fat loss.

Intermittent fasting is also common for its health benefits such as promoting balance in the blood sugar and there are claims that it also promotes longevity. Further more, it is also used for muscle gain and this article will explore how, and the benefits, as well as the disadvantages.

Intermittent Fasting and Its Benefits

Simply put, intermittent fasting is a pattern of eating where one alternates between periods of eating and fasting window that is more than simply missing the odd meal, a prolonged fast. They may completely avoid food (especially that with large numbers of calories) during the fasting period or eat some but in reduced quantities. There are many different types of intermittent fasting, including 16/6, 20/4 and OMAD.

Some benefits accrued to intermittent fasting include:

  1. It initiates necessary changes in the functioning of genes, cells,and hormones. They include:
  2. A reduction in insulin levels in the blood
  3. Increase in the formation and release of the human growth hormone that facilitates burning of fats and gaining of muscles
  4. Repairment of body cells and extraction of cellular waste
  5. Changes in the genes that are associated with longevity
  6. It helps in the loss of weight and belly fat
  7. It reduces insulin resistance which reduces the risk of suffering from Type 2 Diabetes.
  8. It can reduce inflammation and oxidative damage in the body which slows downaging
  9. It is important for cardiac health

Intermittent Fasting and Muscle Gain

Does intermittent fasting actually lead to muscle gain?

To answer that question, it is critical to understand what happens during weight loss. Without exercise, weight loss means loss of both fat mass and lean mass which also includes muscle. Since the primary effect of intermittent fasting is weight loss, it means that it also leads to loss of muscle.

Few studies point toward intermittent fasting muscle gain. Compared to other weight loss diets, however, it is considered the one with the least loss of lean mass.


In one study, 18 men were put under observation with different diet programs. The study subjects were divided into two: one consumed a regular diet and the other a time-restricted diet, all in a four-hour period for four days in a week.

When the study was concluded, the first group (on the standard diet) gained five pounds of pure lean mass. They were also stronger. The other group, however, maintained their lean mass but had also increased their strength. This proved that in a time-restricted diet, less protein is consumed than in a normal diet which suggests that it may not be the best way to gain muscle.

Intermittent Fasting with Weight Training

Nevertheless, it does not mean that it is not possible to gain muscle with intermittent fasting. It is only harder than with other dieting programs. Considering the limited periods of food intake, eating enough protein and calories to build muscle and provide energy may go against the basic principles of intermittent fasting: fewer calories and fewer meals.

A study conducted on 34 men experienced in weight training showed that it could be useful in losing fat mass while maintaining lean mass during intermittent fasting.

Steps you could take to maintain (or develop) your muscle during intermittent fasting include:


As noted in the study mentioned above, weight training is essential in muscle maintenance and development during intermittent fasting. Other studies, however, have shown no significant difference in weight loss during intermittent fasting with or without exercise.

In fact, it has been found to reduce performance in athletes. Training should, therefore, be precise to target the muscles in the most effective way possible.

A Gradual Reduction in Calorie Intake

A sudden cut-off of calories in the diet will cause sudden weight loss which also means a sudden loss of lean mass. The decrease in calorie content should be gradual so that the rate of weight loss is slow.


The diet composition is also crucial. You should make certain that you get enough protein, especially when trying to lose fat mass and gain lean body mass. It is especially important because the body is taken through long periods without receiving appropriate nutrition.

Use of Supplements

Supplements are important in building lean body mass but should be taken in carefully calculated times so as not to interfere with the results of the fasting. During your feeding periods, you could take protein and creatine supplements. Protein supplements are especially useful when you can’t get enough of it from your food. Creatine helps to support the muscles and increase strength, especially during weight training.

It should be pointed out, however, that supplements are not necessary, especially during the fasting period. They may signal the body that you are not fasting which may interfere with the results.

Benefits of Intermittent Fasting Muscle Gain

Improved Insulin Sensitivity During Training

Even though training fasted may interfere with athletic performance, it also helps burn a lot of body fat mass because of a reduction of insulin levels. This could be very beneficial for bodybuilders who may not need to perform like power lifters.

Production of Growth Hormones

Growth hormones helps to burn more fat. It is also helpful in repair and healing of the muscles especially after injuries during vigorous training.

Increased Levels of Testosterone

The more testosterone produced, the more likely you will gain more lean body mass (as long as you are also working out).

Disadvantages of Intermittent Fasting for Muscle Gain

The major drawback of muscle gain using intermittent fasting is limited protein synthesis.

Intermittent fasting leaves a very small window for protein intake. Considering that an optimal synthesis requires at least three servings of protein everyday and a minimum of three hours between each meal, intermittent fasting can pose quite a challenge for muscle gain.

What About the Meal Frequency Theory ? 

If you have been trying to add muscle tissue to your frame for any length of time then you will be familiar with the concept of eating frequently. In fact, the muscle magazines, websites and YouTube ‘experts’ have been pushing the ‘consume protein every 2-3 hours’ to prevent muscle tissue loss and keep yourself in an anabolic state for decades. The only problem is that it’s not true.

Our hunter gatherer forebears went for long periods of time between meals, as they were out hunting for the food that they would eat. During those periods they needed to maintain their energy and their strength. But if they had been getting weaker, losing muscle tissue and slowing their metabolism because they hadn’t eaten for 3 hours, they wouldn’t have had the energy to hunt. If that were the case, the human species would have died out a long time ago!

Science has also debunked the frequent eating to maintain muscle tissue myth. When you fast for short periods of time, your metabolism actually increases. That’s because it is working overtime to break down stored bodyfat into energy in the form of ketones. The reality is that lean muscle tissue will only be consumed by the body when two conditions exist:

  • You are in a state of starvation
  • You have almost zero body fat on your body

To get into a state of starvation you need to be deprived of food for more than 48 hours. Proper intermittent fasting diets for fat loss and muscle gain involve going for that length of time without food. And even if you did, unless your body fat level was sitting at below 5 percent, the body would rely on its stored body fat to provide the energy that you need to function.

Key Fat Loss and Muscle Gain Fasting Tips

  • The majority of your carb consumption on training days should take place during your pre-workout meal (an hour before heading to the gym), during the workout and post workout (an hour after training).
  • For optimum nitrogen retention and maximum glycogen replenishment, aim for 20-40 grams of high-glycemic carbs and an equal amount of protein pre and post workout.
  • Your post workout meal should be the largest of the day. This is when your cell’s glycogen stores will be depleted and your muscle fibers broken down.
  • Expect weight fluctuations. During your fasting windows you will be depleting your glycogen stores. However, on your workout days, you will be consuming a decent amount of carbohydrates in order to replenish your glycogen stores. As a result of this, it would not be abnormal to see an increase of 5-10 pounds when you step onto the scale on a workout day. This just goes to underscore a point made earlier; the scale is not the ideal way to judge your fat loss and muscle gain success. Looking at yourself naked in the mirror is!
  • During your fasting window do not consume any calories at all! Some intermittent fasting programs do allow you to consume such things as MCT Oil, butter, cream or branch chain amino acids. There is some pretty compelling evidence, however, that even these low-calorie foods will curtail the benefits of a fast.

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 In Conclusion

While studies have proved that intermittent fasting could lead to loss of both fat and lean body mass, it could also be done carefully to maintain and even build muscle mass. In this regard, one needs to eat enough protein and incorporate exercise into the diet, even though it could limit athletic performance.

Therefore, it is important these nutrients are eaten during your break the fast period to ensure you don’t lose muscle mass when you want to lose fat only. You can use a macro calculator to help you. A ketogenic diet could help which is essentially a low carb, high fat and adequate protein diet, to learn more read Keto Diet vs. Atkins: What Actually Is the Difference?

It could also be challenging for those with a busy work schedule that depend on cups of coffee (black coffee) or tea to get through the day, on top of the fact they will eat fewer calories. This is important to recognize with water being the only substitute. You may want to consider alternate day fasting.

On a caloric restriction diet you should lose weight fast with a period of continuous days fasting ( fasting during the day with the aim to break the fast in the evening ) with the aim of overall improved health. We hope you enjoyed this article and we have helped to clear up any misconceptions about intermittent fasting. 

Steve Theunissen has qualified from the International Sports Sciences Association (ISSA) and is a certified Personal Trainer and Nutritionist. He has over 30 years experience in fitness and nutrition and currently working with famous fitness professionals. He is currently living in New Zealand with is wife and daughter.

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