Intermittent Fasting | Muscle Loss | Muscle Gain | Keto | FAQ | Studies
Some people in fitness and bodybuilding argue that intermittent fasting makes muscle building impossible.
While some believe intermittent fasting induces muscle loss, others believe eating many small meals improves metabolism.
But as recent studies show, intermittent fasting can be a tool to improve muscle growth if you use it correctly. In this article, you can find out exactly how it works.
What Is Intermittent Fasting 16/8?
Intermittent fasting involves eating within a specific time and fasting during the rest of the day.
Although very different intermittent fasting forms exist, fasting within a time window of around 16 hours is by far the most popular.
Because it allows you to build muscle mass and lose body fat simultaneously, 16/8 intermittent fasting is known as the Lean Gains Method or Peak Fasting.
For example, you eat between noon and 8 pm. This way, your gastrointestinal tract can rest for the remaining 16 hours of the day.
After you sleep 8 of the 16 fasting hours, intermittent fasting is more comfortable than many assume.
Therefore, to begin regular 16/8 intermittent fasting, you only need to skip breakfast.
Contrary to popular belief, breakfast is far from mandatory due to the energy boost from hormone release in the morning.
Due to increased adrenaline, cortisol, glucagon, and growth hormone levels, we wake up in the morning.
In conclusion, breakfast is the most important meal of the day for the food industry, but not for you. Nevertheless, Intermittent Fasting is flexible and can be customized to fit your daily routine.
Besides 16/8 intermittent fasting, the following intermittent fasting protocols are widely used:
- One-Day Fasting (6:1 Diet) – you do not eat anything on a full day a week
- Two-Day Fasting (5:2 Diet) – you do not eat for two days (often with a small meal)
- Alternate Day Fasting (ADF) – Eat one day, fast one day (often with a small meal)
- One Meal A Day (OMAD) – 23/1 intermittent fasting, where you eat once a day
Intermittent Fasting: Muscle Gain or Loss?
Contrary to popular belief, fasting does not cause muscles to atrophy.
The misconception that fasting destroys muscles arose because your body can break down protein and use it for energy when fasting sufficiently long.
However, this is not muscle protein. Instead, the body focuses on defective proteins, for example, in the skin or intestinal mucosa.
In this way, the body obtains amino acids that you otherwise supplied with food.
This recycling of broken cell parts, which starts at the earliest after 14 hours of fasting, is instead a detox and repair of the body than a danger for your lean mass (Yang et al. 20171).
Moreover, this process of autophagy also protects against muscle breakdown (Jiao et al. 20172).
Indeed, many of our metabolic pathways are designed to conserve muscle mass at all costs.
When you fast, the body preferentially consumes stored carbohydrates (glycogen) because it can mobilize them most quickly.
When you empty these glycogen stores, your body taps into fat for energy.
This natural process of fat burning is called ketosis. In addition to intermittent fasting, exercise induces ketosis, preventing muscle loss, according to recent studies (Paoli et al. 20193).
Furthermore, the body releases so-called counter-regulatory hormones to protect lean mass during fasting,
One of these is the human growth hormone (HGH). During fasting, the release of growth hormone peaks to ensure you don’t lose muscle mass.
Simultaneously, intermittent fasting protects against muscle loss and protects bone mass from degeneration (Rudman et al. 19904).
How to Gain Muscle on Intermittent Fasting
Since intermittent fasting helps maintain muscle mass, you can use it specifically to build muscle.
For a good reason, 16/8 Intermittent Fasting is called the Lean Gains Method. In bodybuilding, it has been used for decades to build muscle mass without gaining body fat precisely.
By following the points below, you, too, can master this task and even lose body fat in the process.
1. Exercise Fasted
Few authors want to give you this vital point – mainly if they sell sports nutrition.
The human body has three primary nutrient sensors, shifting it from a catabolic (breaking down) to an anabolic (building up) state.
Accordingly, the body is busy breaking down stored energy in a fasted state. These are stored carbohydrates (glycogen), body fat, and dysfunctional cellular parts (proteins).
You can read about exactly how this works in my article on autophagy.
However, when you eat before exercising, you activate the nutrient sensor insulin. And as the name suggests, the storage hormone is responsible for building up energy stores.
Insulin also blocks the enzyme that can break down stored body fat (Meijssen et al. 20015).
Also, the body preferentially consumes the energy supplied by food in the bloodstream. Ultimately, it would be much more helpful to burn stored body fat instead.
Therefore, there are only two fundamental reasons to eat before exercise:
- You intend to build body fat in addition to lean mass
- You are a professional athlete who trains several times a day and needs additional energy
Therefore, amateur sports’ ubiquitous orientation to competitive sports has kept countless people from getting into shape over and over again.
Since sports also help you get into ketosis, you can burn fat even more efficiently when exercising in a fasted state.
In the same way, exercise also promotes autophagy.
Therefore, you can maximize the health benefits of intermittent fasting by exercising in a fasted state. And these range from cancer prevention and improved insulin sensitivity to an overall increase in life expectancy.
Last but not least, fasted training helps you maximize growth hormone release. As a result, you gain muscle much more effectively.
2. Elevate Growth Hormone
Fasting is one of the most effective ways to stimulate HGH naturally (Ho et al. 19886).
HGH promotes bone, cartilage, and muscle growth. As a result, you get bigger, stronger muscles and protection from age-related bone and muscle loss.
In short, intermittent fasting is a kind of anabolic bio-hacking.
You maximize the release of growth hormones until you break the fast after training and send the body into an anabolic state at the right time for targeted muscle growth.
If you also eat the right natural foods, such as fatty fish, the body will get everything it needs for improved muscle building during intermittent fasting:
- Growth Hormone
- Healthy fats
With the natural release of growth hormone decreasing as we age, intermittent fasting is becoming increasingly crucial for muscle gain.
It helps muscle recovery after exercise and sets the stage for healthy bones, organs, and long life (Besson et al. 20037).
3. Do Not Restrict Calories
Fasting is not about how much you eat but instead WHEN you eat.
On the one hand, it means you eat specifically after your workout. On the other hand, it means you don’t eat during the fasting period before exercising because even small meals raise insulin levels.
Hence, conventional diet advice often prevents fat loss through exercise.
Besides, intermittent fasting does not require calorie reduction, as many people would like to believe. It merely involves timing calorie intake to favor fat loss and muscle gain hormonally.
If you only eat two instead of three times a day, your meals will automatically get bigger. For some people, this may still result in a slight calorie deficit.
However, if muscle building is your stated goal, intermittent fasting 16/8 does not require you to hold back during the eating period. Instead, you concentrate your daily needs on a specific period.
Although conventional calorie restriction can lead to weight, it leads to fat gain and muscle loss in the long term. Besides, the basal metabolic rate decreases when you eat less but frequently (Fothergill et al. 20168).
Unfortunately, the human body is still often reduced to a combustion engine. Nevertheless, it is controlled by hormones. And this fact applies to both muscle building and fat loss.
4. Boost Your Metabolism
Contrary to the popular belief that intermittent fasting slows metabolism, research has long shown that it improves it (Drenick et al. 19649).
After fasting releases growth hormones and norepinephrine, our ancestors could forage longer for food when their stomachs were empty (Ho et al. 198810).
Thus, they could ensure our species’ survival when food was scarce.
Besides, this increased hormone release improves the basal metabolic rate, according to science (Zauner et al. 200011).
As a result, intermittent fasting can also help burn body fat more efficiently.
5. Burn Off Critical Fat
Both fasting and exercise force your body to burn off stored sugars and tap into body fat for energy.
When released fatty acids from body fat or food enter the liver, they are converted into ketones to provide energy for the body.
Therefore, ketosis supported by intermittent fasting can burn fat reserves even faster (Paoli 201512).
But intermittent fasting does not just burn uncomfortable fat deposits.
Accordingly, recent studies state intermittent fasting burns dangerous visceral fat more effectively than a low-carb diet (Catenacci et al. 201613).
Visceral fat accumulates in and around vital organs, such as the liver, intestines, or pancreas. Thus, this intra-organ fat contributes to fatty liver, type 2 diabetes, and cardiovascular disease (Bray et al. 200714).
Since the liver is the first place where visceral fat accumulates, it can lay the foundation for other metabolic diseases there through insulin resistance.
6. Gain Flexibility
People are diverse. Even if we share the common goal of using intermittent fasting to help build muscle, we often have different motivations.
While some people want to lose fat by building muscle, others aim to maximize athletic performance.
The latter may not always want to avoid carbohydrates, as they continually deplete their glycogen stores repeatedly, and dietary carbohydrates may contribute to muscle recovery (Murray et al. 201815).
With this in mind, flexible fasting intermittents and carbohydrate intake can support your training:
- Intense training day: Longer eating periods and more carbohydrates, which can again directly replenish muscle glycogen stores
- Rest and fasting day: No or shorter eating periods on a low-carb diet
Accordingly, carb-cycling or a cyclic ketogenic diet can help you adapt your intermittent fasting plan to special athletic needs.
Nonetheless, carb refeed days are not mandatory for muscle growth as long as protein intake is provided (Koopman et al. 200716).
Although the increased insulin levels from carbohydrates can help muscles recover, it also helps build body fat faster (Shah et al. 201117).
For this reason, some bodybuilders claim they can’t gain muscle without building up fat.
Therefore, amateur athletes and those who want to get in the best shape with little effort are usually better off with a ketogenic diet.
Gaining Muscle on Intermittent Fasting and Keto
If low body fat and increased longevity are the main reasons you want to boost muscle gain through intermittent fasting, a ketogenic diet best supports these goals.
Since fasting burns your body fat for energy, it is the most ketogenic diet. Therefore, keto can be an excellent complement to intermittent fasting.
A ketogenic diet is defined by energy intake from the three macronutrients:
- 75% from fat
- 20-25% from proteins
- 5-10% from carbohydrates
However, a higher caloric intake from protein may be exceptional for targeted muscle gain through weight lifting:
- 1.6 to 2.2 g protein per kg of body weight per day for resistance training
- 1.6 to 3.3g protein per kg daily for bodybuilders and elite athletes
Nevertheless, it is essential to train in a fasted state and supply proteins after exercising, preferably through whole foods.
Intermittent Fasting Improves Muscle Gain Without Effort
Intermittent fasting does not make your muscles atrophy.
Quite the opposite – adequately applied, intermittent fasting sets the hormonal course to achieve maximum muscle gain and fat loss with minimal exercise.
But that doesn’t mean you can leverage it to gain heaps of lean mass when exercising enthusiastically. However, it is essential to train in a fasted state and eat proper whole foods.
And contrary to popular belief, you don’t have to starve, count calories, or prepare meals all the time.
Accordingly, the best thing about intermittent fasting is the freedom that comes with it.
Therefore, you can always customize your intermittent fasting schedule to fit your exercise plan and promote gaining muscle in the best possible way.
To start gaining muscles faster today, check out my 30-Day Intermittent Fasting Challenge and take advantage of the increased growth hormone release.
Gain Muscle on Intermittent Fasting FAQ
Can you build muscle while intermittent fasting?
It is possible to build muscles while fasting. In bodybuilding, intermittent fasting 16/8 has been used for decades as the so-called “lean gains method.”
What should I eat to gain muscle while intermittent fasting?
Avoid refined carbohydrates (e.g., bakery) and replace them with natural protein and healthy fat sources (e.g., fatty fish, grass-fed beef, olive oil, avocados).
Is intermittent fasting good for bodybuilding?
Since it spikes human growth hormone 4-5 times as much as exercise, intermittent fasting is an excellent bodybuilding option.
How do you get enough protein when intermittent fasting?
You get enough protein on intermittent fasting the same way as without – by eating. Intermittent fasting does not mean eating less. Eating within a specific time window means setting hormone balance to promote muscle gain.
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This Post Has 19 Comments
What a fantastic article. I quickly read through a few other websites claiming to know about this, but it was clear they were just reguritating info.
Thank you for this brilliantly written piece.
Thank you for the great feedback! It definitely made my day 🙂 And I am delighted that the information was useful to you!
Thanks and best regards,
Hi Stephan, so we can build up muscles while being in a caloric deficit through intermittent fasting – is that right?
Thank you for the question 🙂
The longer you fast, the higher is the level of growth hormone secretion and hence muscle conservation. For this reason, strict periods of intermittent fasting can help you maintain/build muscle on a caloric deficit while reducing body fat percentage. However, there is no need for a vast caloric deficit due to low insulin levels during fasting.
On the 16/8 fasting schedule how many meals do you recommend? I’m thinking if I only eat two that won’t be enough calories. Thanks for all your research!
Thanks for the interesting question.
In my opinion, it’s a matter of routine if you can fit enough calories into two meals. I even go with only one meal most of the time, where I eat up to 1,5 kg food ^^
However, my current focus is not bulking, and you can feel free to eat more than two times within the 8 hours of eating. How about some experimenting? You could do an A/B test: 2 meals a whole week, 2+ meals the other.
I am sure you will figure out what feels best for your body with such an approach.
Wow Stephan, this is incredibly insightful. Learned a lot by reading it. I have started fasting because of the podcasts of David Sinclair on longevity, and was worried it would make me lose too much muscle. You have given me confidence to continue on. Thanks!
Great to hear that my article could help you out. Are there more worries that come with starting fasting? I have made a comprehensive article about intermittent fasting myths debunked by science.
That the information gave you the confidence to continue made my day – have a great one yourself!
Thank you so much for summarizing all of the information. This is the best article I found in this topic. I have to comment on this page to promote it!
Thanks for the effort to send me your cheerful words! I am delighted that the information could help you out!
Have a great day and best regards,
Hello, thanks for this study! I have question tho, If I fast until lunch and train in the evening, will my muscles be compromised the next day and only recover after I eat at lunch? Thanks again!
Thanks for your cheerful words and this question 🙂
I cannot derive from your words if you are eating dinner. After the evening workout, having a meal high in proteins and B vitamins will definitely support muscle recovery overnight.
Thank you very much! Yes, I train right before having a snack and two hours later I have my dinner and only eat the next day at lunch, I was worried that my muscles would only repair if I was constantly eating every few hours, because I feel great since I started doing intermittent fasting.
thanks for the appreciation 🙂
Now that I understand your concern better, here’s my article about the Top 10 Intermittent Fasting Myths Debunked by Science that is precisely tackling the topic at #5.
Have a great day,
Finally!! I had to work through a lot of BS to find this article. May i pose a few further questions privately?
sure, feel free to ask 🙂
hey..will the 20/4 method affect muscle Mass?
I am on at least 20/4 daily and an all-time high in lean mass 🙂 So in my experience, it will affect muscle mass in a positive way.
I am on at least 20/4 daily and at an all-time high in lean mass 🙂 So in my experience, it will affect muscle mass in a positive way.