|Want to promote muscular and overall health? Do this after an 8h+ fast.|
But who wants to "deconstruct" muscle, anyway?
Now, from the gymbro perspective the most important aspect of the training induced adaptation processes would probably be protein synthesis. And while you can actually argue that this was the case if things were just about "growing", a different picture emerges, when you look at health benefits and the actual remodeling process which does necessarily begin with "demodeling", or rather the demolution of old muscle tissue - when that's happening in a controlled self-induced (by the cell) manner, scientists call this process autophagy.
Autophagy is one of the main reasons fasting is good for you
Now, when cells "kill" themselves, they usually do that for a reason. In fact, the process of autophagy must be seen as part of the general housekeeping - a part with enormous importance, as one of the possible consequences of its failure is cancer. Moreover, it has been demonstrated only recently that autophagy is also an essential process for muscle adaptation:
That being said, a group of researchers from the Université catholique de Louvain in Belgium set out to study whether the two major pro-apoptotic mechanisms in our lives, i.e. working out and fasting would complement each other so that their effects add up and you get the double dose of healthy - and as you have learned today "muscle (re-)building" cell death.
"Autophagy is activated in skeletal muscle by numerous catabolic stimuli such as food deprivation, denervation or sepsis. However, evidence for the necessity of basal autophagy level in the maintenance of myofibrillar integrity has counterbalanced the vision of a system only implicated in muscle wasting. Very recently, the activation of the autophagy-lysosomal pathway has emerged as an essential process for skeletal muscle adaptation after endurance training (Lira. 2013)." (Jamart. 2013)
Suggested read: "If a High Fat Diet was a Pill, the Lay Press Would Celebrate it as 'Exercise in a Pill'" | read more
Can you combine it? Yes you can!
As you can see in figure 1 the answer is clear: Yes, you can - meaning you can combine fasting and exercise and achieve an even greater activation of the autophagy-lysosomal pathway .
And what about humans? Do we have reason to believe this would not happen in human beings? Of course we do, but it is actually very unlikely that there will be major differences in the intra-muscular response to fasting. Plus, we do have human studies showing related benefits that are exclusive to fasted training, already (see "bottom line").The data in figure 1 arose from the observations the researchers made, when they had a group of rodents perform a 90 min run at a speed of 10m/min (I did not plot the increases in markers of autophagy like Gabarapl1-II, Atg12, Lc3b, Gabarapl1 and p62/Sqstm1, simply because I don't think they are useful for you - take it for granted that those were only increased in the fasted state).
|Figure 1: Comparison of selected markers of celluar and mitochondrial autophagy (mitophagy) in mice before and after 90min run in the fasted or fed state (Jamart. 2013)|
But is this even a good thing? Now, I can already see you struggling with the idea of voluntarily inducing "catabolism" - that's stupid right? Yes, you are right, it is in fact stupid to think about autophagy this way. This is not a non-selecive process that kills valuable muscle tissue like sarcopenia, it's a necessary prerequesite for the structural integrity of your muscle (get rid of the junk, build new stuff in place) and your whole body. The ability to boost local the systemic activation of the autophagy-lysosomal pathway is thus in fact a definitive plus you don't want to miss, but don't want to overtax, either (don't do it everyday, don't do it in combination with a high caloric deficit, don't forget to refuel after the workout).
|Suggested read: "3x30s High Intensity Intervals Increase mTOR & Ramp Up Marker of Protein Synthesis - Even in a Fasted State!" | read more|
Said study by van Proyen was by the way the first to prove that fasted training is more potent than fed training to facilitate adaptations in muscle and to improve whole-body glucose tolerance and insulin sensitivity during hyper-caloric fat-rich diet. So, I suggest you remember it, when you wake up tomorrow and think about whether you should go for a run now or rather after filling up your belly with some delicious eggs or whatever it is that you have for breakfast.
- He C, Bassik MC, Moresi V, Sun K, Wei Y, Zou Z, An Z, Loh J, Fisher J, Sun Q,
Korsmeyer S, Packer M, May HI, Hill JA, Virgin HW, Gilpin C, Xiao G, Bassel-Duby
R, Scherer PE, and Levine B. Exercise-induced BCL2-regulated autophagy is required
for muscle glucose homeostasis. Nature481: 511-515, 2012.
- Jamart C, Naslain D, Gilson H, Francaux M. Higher activation of autophagy in skeletal muscle of mice during endurance exercise in the fasted state. Am J Physiol Endocrinol Metab. 2013 Aug 20. [Epub ahead of print]
- Lira VA, Okutsu M, Zhang M, Greene NP, Laker RC, Breen DS, Hoehn KL, and Yan Z. Autophagy is required for exercise training-induced skeletal muscle adaptation and improvement of physical performance. FASEB J, 2013.
- Van Proeyen K, Szlufcik K, Nielens H, Pelgrim K, Deldicque L, Hesselink M, Van Veldhoven PP, Hespel P. Training in the fasted state improves glucose tolerance during fat-rich diet. J Physiol. 2010 Nov 1;588(Pt 21):4289-302.
- Van Proeyen K, Szlufcik K, Nielens H, Ramaekers M, Hespel P. Beneficial metabolic adaptations due to endurance exercise training in the fasted state. J Appl Physiol. 2011 Jan;110(1):236-45. doi: 10.1152/japplphysiol.00907.2010. Epub 2010 Nov 4.