Intermittent Fasting and Muscle Loss


intermittent fasting and muscle loss

Intermittent Fasting and Muscle Loss

As the interest in fasting has increased, so have the myths and misconceptions. There is a large group of “fitness and nutrition experts” who feel personally threatened because it undermines their previous advice. Can you blame them?

After preaching, “6 small meals,” “never skip breakfast,” and “don’t go catabolic,” how would they look admitting that they were wrong? Enter the haters!

Bring up fasting to a bodybuilder and they will tell you it eats muscle (um ok…)

Bring up fasting to a nutritionist and they will tell you its unhealthy to skip meals (um quite the opposite)

Bring up fasting to a random person  and they will warn you that not eating makes you fat (???)

Sadly, you don’t know, what you don’t know. What does that even mean? I took undergraduate and graduate level nutrition courses. In all of those courses, I was never once presented with any of the research on fasting, metabolic flexibility, or high protein diets. Yet, all of this research exists and has shown to be effective. What gives?

This is because our textbooks are all about 10-20 years behind what’s actually happening today. Academic myopia – they teach you what they want you to know. They also teach you what they were taught. It’s just laziness. I mean, the RDA of protein is still around 46g a day (lol). Go ask any person who is in great shape how they diet and I guarantee you their diet includes more protein than that.

Fasting for Muscle?

There’s always two sides to every argument and then there’s a truth right in the middle. Opponents of fasting often claim that intermittent fasting leads to catabolism which then automatically leads to muscle loss. But hold on a minute.

First off, the definition of catabolism is not necessarily muscle loss, even though that’s the only context you see it in. Catabolism refers to certain molecules being broken down to provide energy. Protein isn’t the only thing that’s available to be used here but so are lipids (fats) and polysaccharides. This is a completely normal process and it’s a necessity for our bodies.

In terms of muscle loss, the study, “Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss,” found that an intermittent fasting diet lead to more lean mass being retained vs. a diet of daily calorie restriction. [1] Numerous studies on Ramadan also show that fat free mass is retained quite well in regards to fasting [2].

(Oh no, look at all the muscle I lost from fasting!)

But if you want muscle you’re still probably wondering why we would ever want to stop protein synthesis, right? In order for us to gain muscle, protein synthesis (the creation of new proteins) must be greater than protein degradation (the breakdown of proteins). Luckily for us, the body undergoes some unique changes during the halt of nutrients that actually protect muscle quite effectively if it’s planned properly.

One way to explain this is the increase in growth hormone that is seen during a fast period [3, 4]. Growth hormone decreases amino acids being broken down for energy (oxidation), which preserves amino acids and allows them to continue to build new proteins.

Because of this, growth hormone has a positive impact on protein synthesis. There are also increases in SIRT-1 and mitochondrial biogenesis that have a positive effect on muscle growth [5]. I am not saying this release of GH will put slabs of muscle on you, simply that it will help protect your muscle tissue during a fast.


Autophagy and Muscle

Autophagy is a word I’ve thrown around when writing about fasting so what exactly is it? Put simply, autophagy means “self – eating”, as auto means self in Greek and phagy is abbreviated for eating.  It is a catabolic process that helps rid the body of unneeded and possibly dysfunctional cellular debris.  So why does this happen?

Remember, hundreds of years ago food wasn’t as accessible as it is today. Our body needed ways to cope with stretches of no food intake. As more time passes with no food, your cells will start to eat or digest themselves. Don’t panic, this is actually healthy and normal (within reason). Your cells can actually use old proteins to recycle and release amino acids out into your bloodstream [6].

Autophagy is initiated when the cell is starved and lacking nutrients or even under normal conditions when the body needs to remove damaged proteins and organelles in response to possible cell damage [6].  There seems to be a potential link between autophagy and disease which makes sense given the research that is emerging about so many diseases potentially being metabolic in nature.  But let’s get back to things that are more important, like muscle building….(sarcasm).

Right now you’re probably thinking, “A catabolic process where my body is starving and eating itself, my poor muscle has no chance.” Wrong.  Although most of the attention autophagy garners is due to its beneficial health and anti-aging effects; it actually helps preserve muscle massI will leave you with some quotes from two interesting studies on autophagy and muscle.

  • “Autophagy inhibition exacerbated muscle loss during denervation and fasting. Thus, autophagy flux is important to preserve muscle mass and to maintain myofiber integrity.” [7]
  • “Moreover, autophagy inhibition does not protect skeletal muscles from atrophy during denervation and fasting, but instead promotes greater muscle loss. In conclusion, autophagy plays a critical role for myofiber maintenance and its activation is crucial to avoid accumulation of toxic proteins and dysfunctional organelles that, in the end, would lead to atrophy and weakness.” [8]

This is just further evidence that you do not need to lose sleep over muscle loss in short periods of fasting as your body has plenty of mechanisms to keep what it deems as important!

A lot of the benefits of fasting are due to allowing our body to clean itself out from the 20th century, eat until you can’t breathe lifestyle. A fast is the only true detox out there.  So it’s painful watching people throw thousands in the trash to buy scam detox and cleanse products that promise miracles and leave you with nothing but less money and dignity. Hopefully by now you can appreciate some of the beneficial effects of catabolic processes that occur during periods of fasting.

Lastly, when you hear these claims PLEASE ask for some evidence to support it. As you can see in this brief article, I am not just stating an opinion, I am also providing further research. It’s easy to dole out blanket, anecdotal advice without ever being held accountable. Do your own research and think for yourself!

You might also be interested in:

Intermittent Fasting and Cortisol


[1] Varady, KA. “Intermittent versus Daily Calorie Restriction: Which Diet Regimen Is More Effective for Weight Loss?” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web.

[2]Chaouachi, A. Leiper JB. “The effects of Ramadan intermittent fasting on athletic performance: recommendations for the maintenance of physical fitness.” Journal of Sports Science. 2012.

[3] Groschi, M. “Endocrine Responses to the Oral Ingestion of a Physiological Dose of Essential Amino Acids in Humans.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 01 Oct. 2015.

[4] Muller, A., S. Lamberts, J. Janssen, L. Hofland, P. Koetsveld, M. Bidlingmaier, C. Strasburger, E. Ghigo, and A. Van Der Lely. “Ghrelin Drives GH Secretion during Fasting in Man.” European Journal of Endocrinology 146.2 (2002): 203-07. Web.

[5] Tonkin, J. “SIRT1 Signaling as Potential Modulator of Skeletal Muscle Diseases.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 01 Oct. 2015.

[6] Castro-Obregon, Susana. “The Discovery of Lysosomes and Autophagy.” Nature Publishing Group, n.d. Web.

[7] Masiero, E., and L. Agatea. “Autophagy Is Required to Maintain Muscle Mass.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web.

[8] Masiero, E., and M. Sandri. “Autophagy Inhibition Induces Atrophy and Myopathy in Adult Skeletal Muscles.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web

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