There are always people who argue that muscle building is impossible with intermittent fasting in the fitness and bodybuilding field.
While some believe that intermittent fasting induces muscle loss, others believe that 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. You can find out exactly how it works here.
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 also 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 people assume.
Therefore, to begin regular 16/8 intermittent fasting, all you need to do is 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 on 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 for a sufficiently long time.
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.
Only when these glycogen stores are empty, your body taps into fat for energy.
This natural process of fat burning is called ketosis. In addition to intermittent fasting, exercise also 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 make sure 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 also 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. Fasted Exercise Supports Your Goals
Few authors want to give you this vital point – mainly if they sell sports nutrition.
The human body has three primary nutrient sensors that, shifting it from a catabolic (breaking down) into an anabolic (building up) state when activated.
Accordingly, in a fasted state, the body is busy breaking down stored energy. 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 then preferentially consumes the energy supplied by food in the bloodstream. In the end, it would be much more useful 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 and thereby muscle gain.
2. Fasting Elevates Human 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.
Not only does it help with muscle recovery after exercise, but it sets the stage for healthy bones, organs, and long life (Besson et al. 20037).
3. Intermittent Fasting Differs From Calorie Restriction
Fasting is not about how much you eat, but rather 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. It Boosts Metabolism
Contrary to the popular belief that intermittent fasting slows metabolism, research has long shown that it improves it instead (Drenick et al. 19649).
After fasting releases growth hormones and norepinephrine, our ancestors could forage longer for food precisely when their stomachs were empty (Ho et al. 198810).
Thus, they were able to ensure the survival of our species when food was scarce.
Besides, it is precisely this increased hormone release that 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. Intermittent Fasting Burns 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 that intermittent fasting burns dangerous visceral fat more effectively than a low-carb diet does (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. The Flexibility of Fasting Supports Your Gains
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 by doing so.
The latter may not always want to avoid carbohydrates, as they are continually depleting 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 individual 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 that they can’t gain muscle without building up body 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 Keto and Intermittent Fasting
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 of them all. 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 that 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 yourself, 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.
Gain Muscle 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 the exercise itself, 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. It means to eat within a specific time window, setting hormone balance to promote muscle gain.
1Yang JS, Lu CC, Kuo SC, Hsu YM, Tsai SC, Chen SY, Chen YT, Lin YJ, Huang YC, Chen CJ, Lin WD, Liao WL, Lin WY, Liu YH, Sheu JC, Tsai FJ. Autophagy and its link to type II diabetes mellitus. Biomedicine (Taipei). 2017 Jun;7(2):8. doi: 10.1051/bmdcn/2017070201. Epub 2017 Jun 14. PubMed PMID: 28612706; PubMed Central PMCID: PMC5479440.
2Jiao J, Demontis F. Skeletal muscle autophagy and its role in sarcopenia and organismal aging. Curr Opin Pharmacol. 2017 Jun;34:1-6. doi: 10.1016/j.coph.2017.03.009. Epub 2017 Apr 10. Review. PubMed PMID: 28407519.
3Paoli A, Cancellara P, Pompei P, Moro T. Ketogenic Diet and Skeletal Muscle Hypertrophy: A Frenemy Relationship?. J Hum Kinet. 2019 Aug;68:233-247. doi: 10.2478/hukin-2019-0071. eCollection 2019 Aug. PubMed PMID: 31531148; PubMed Central PMCID: PMC6724590.
4Rudman D, Feller AG, Nagraj HS, Gergans GA, Lalitha PY, Goldberg AF, Schlenker RA, Cohn L, Rudman IW, Mattson DE. Effects of human growth hormone in men over 60 years old. N Engl J Med. 1990 Jul 5;323(1):1-6. doi: 10.1056/NEJM199007053230101. PubMed PMID: 2355952.
5Meijssen S, Cabezas MC, Ballieux CG, Derksen RJ, Bilecen S, Erkelens DW. Insulin mediated inhibition of hormone sensitive lipase activity in vivo in relation to endogenous catecholamines in healthy subjects. J Clin Endocrinol Metab. 2001 Sep;86(9):4193-7. doi: 10.1210/jcem.86.9.7794. PubMed PMID: 11549649.
6Ho KY, Veldhuis JD, Johnson ML, Furlanetto R, Evans WS, Alberti KG, Thorner MO. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 1988 Apr;81(4):968-75. doi: 10.1172/JCI113450. PubMed PMID: 3127426; PubMed Central PMCID: PMC329619.
7Besson A, Salemi S, Gallati S, Jenal A, Horn R, Mullis PS, Mullis PE. Reduced longevity in untreated patients with isolated growth hormone deficiency. J Clin Endocrinol Metab. 2003 Aug;88(8):3664-7. doi: 10.1210/jc.2002-021938. PubMed PMID: 12915652.
8Fothergill E, Guo J, Howard L, Kerns JC, Knuth ND, Brychta R, Chen KY, Skarulis MC, Walter M, Walter PJ, Hall KD. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity (Silver Spring). 2016 Aug;24(8):1612-9. doi: 10.1002/oby.21538. Epub 2016 May 2. PubMed PMID: 27136388; PubMed Central PMCID: PMC4989512.
9DRENICK EJ, SWENDSEID ME, BLAHD WH, TUTTLE SG. PROLONGED STARVATION AS TREATMENT FOR SEVERE OBESITY. JAMA. 1964 Jan 11;187:100-5. doi: 10.1001/jama.1964.03060150024006. PubMed PMID: 14066725.
10Ho KY, Veldhuis JD, Johnson ML, Furlanetto R, Evans WS, Alberti KG, Thorner MO. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 1988 Apr;81(4):968-75. doi: 10.1172/JCI113450. PubMed PMID: 3127426; PubMed Central PMCID: PMC329619.
11Zauner C, Schneeweiss B, Kranz A, Madl C, Ratheiser K, Kramer L, Roth E, Schneider B, Lenz K. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. Am J Clin Nutr. 2000 Jun;71(6):1511-5. doi: 10.1093/ajcn/71.6.1511. PubMed PMID: 10837292.
12Paoli A, Bosco G, Camporesi EM, Mangar D. Ketosis, ketogenic diet and food intake control: a complex relationship. Front Psychol. 2015;6:27. doi: 10.3389/fpsyg.2015.00027. eCollection 2015. Review. PubMed PMID: 25698989; PubMed Central PMCID: PMC4313585.
13Catenacci VA, Pan Z, Ostendorf D, Brannon S, Gozansky WS, Mattson MP, Martin B, MacLean PS, Melanson EL, Troy Donahoo W. A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity (Silver Spring). 2016 Sep;24(9):1874-83. doi: 10.1002/oby.21581. PubMed PMID: 27569118; PubMed Central PMCID: PMC5042570.
14Bray GA, Jablonski KA, Fujimoto WY, Barrett-Connor E, Haffner S, Hanson RL, Hill JO, Hubbard V, Kriska A, Stamm E, Pi-Sunyer FX. Relation of central adiposity and body mass index to the development of diabetes in the Diabetes Prevention Program. Am J Clin Nutr. 2008 May;87(5):1212-8. doi: 10.1093/ajcn/87.5.1212. PubMed PMID: 18469241; PubMed Central PMCID: PMC2517222.
15Murray B, Rosenbloom C. Fundamentals of glycogen metabolism for coaches and athletes. Nutr Rev. 2018 Apr 1;76(4):243-259. doi: 10.1093/nutrit/nuy001. Review. PubMed PMID: 29444266; PubMed Central PMCID: PMC6019055.
16Koopman R, Beelen M, Stellingwerff T, Pennings B, Saris WH, Kies AK, Kuipers H, van Loon LJ. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. Am J Physiol Endocrinol Metab. 2007 Sep;293(3):E833-42. doi: 10.1152/ajpendo.00135.2007. Epub 2007 Jul 3. PubMed PMID: 17609259.
17Shah PK, Mudaliar S, Chang AR, Aroda V, Andre M, Burke P, Henry RR. Effects of intensive insulin therapy alone and in combination with pioglitazone on body weight, composition, distribution and liver fat content in patients with type 2 diabetes. Diabetes Obes Metab. 2011 Jun;13(6):505-10. doi: 10.1111/j.1463-1326.2011.01370.x. PubMed PMID: 21272186; PubMed Central PMCID: PMC3580155.