mTOR Pathway to More Muscle

supplement capsules If you’re into supplements, chances are you will have come across the term ‘mTOR’ at some point. The manufacturers will use it as a selling point – something like ‘…product X activates the mTOR pathway to give you monster muscle gains…’

Between the bro-science and the promises of getting ‘huge’, there’s not much to go on from the product website if you just want to grasp the basics of what this mTOR stuff is all about. Researching the term yields a bunch of science papers that might tire you out after the first sentence of technical talk.

Given the claims about this…thing…it might help to know a little more. So what is mTOR?

What is mTOR?

The mammalian target of rapamycin (or mechanistic target of rapamycin, depending on your mood) is actually just an oddly named protein. Rapamycin was discovered to suppress the immune system, and is used for that purpose after organ transplant surgery to prevent the patient’s own immune system from rejecting the new organ.

The target of Rapamycin (mTOR) is however the protein we are talking about, and that is one of the most fundamental and vital proteins we have in our bodies. Controlled by a gene bearing the same name, mTOR regulates processes like protein synthesis and cell growth, proliferation, survival etc.

In the context of muscle building, it’s a really big deal, but it’s nothing we don’t already know. If you know that proteins like branched chain amino acids can help your muscles grow after exercise, then you already know about mTOR, you just might not have known you knew.

Actually, mTOR can regulate and integrate into cells the actions of several other mediators, like insulin, insulin-like growth factors 1 and 2 (IGF-1 and IGF-2), and amino acids – specifically Leucine. Whatever role each of these agents play along the chain of events which leads to larger, stronger muscle, it is safe to assume they are all extremely important.

Prime Male 4 for 3Anabolic muscle growth and mTOR signalling in particular is not limited to once supplement or even one ingredient. There are many proven compounds which have the ability to trigger significant growth response from the stimulus of resistance weight training.

An example is Leucine, which is garnering more attention than it has for a while. This essential branched chain amino acid has long been known to reduce the catabolism of muscles intra and post-workout, but any even heavier emphasis is now being placed on its interactions with the mTOR pathway.

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What Does That Mean For Me?

free squatEverything and nothing, is the mysteriously unhelpful answer. Do you need to concern yourself about the microscopic actions of your mTOR, or insulin, IGFs and amino acids for that matter? No. Of course not. You just need to look after yourself on a macro level, i.e. your macro-nutrients: Carbohydrates, Protein, and Fat.

The biggest mistake people make is thinking muscle growth is all about protein intake. Protein is key, but it’s not even half the picture. And once you have enough protein for your requirements, it’s best not to go too much above that otherwise it will start to be converted and stored as fat.

Carbohydrates – and insulin’s reaction to them – are as important, if not more important, than protein intake. Proper fuelling before, during and after exercise with appropriate carbs alongside the optimal quantity of protein is the foundation of muscle building. Omega 3 and Omega 6 fats are also vital in the right moderation. That’s what you can do, then mTOR will do what it does.

mTOR Paradox

Research on small mammals like mice has indicated that inhibition of mTOR activity can extend lifespan. As mentioned briefly earlier, Rapamycin is used as an inhibitor to help prevent a transplant patient’s immune system from rejecting new organs. It’s also believed to reduce the onset of cancer, which is assumed to be part of the life extension equation. The genetically altered mice displayed other anti-ageing benefits as well: they gained better memory and coordination as well.

Survival of mammals depends on the activity of mTOR – so the gene could not be totally disabled – yet its inhibition may serve to increase life span. At least, it can in mice.

Take from that what you will, but maybe that increased muscle and strength may not directly equate to a longer life!

What about the Supplements Claiming to Boost mTOR activity?

That’s an interesting point. Any supplement containing something as simple as Leucine could be said to be activating the mTOR pathway, because the anti-catabolic actions of this BCAA (Branched Chain Amino Acid) are indeed mediated/regulated/integrated by mTOR.

The problem for the supplement companies is that Leucine is not as expensive as it was now, and they can’t make massive profit, so they need to be on constant lookout for new ingredients. Recently, they think they’ve found one.

Phosphatidic Acid

Most of the newer supplements that claim to accelerate the mTOR pathways are full of Phosphatidic Acid. A component of mTOR’s activation is the signal sent in response to resistance training. The cells that receive the stimulus of weight training release Phosphatidic Acid, which then binds to the main complex (Complex 1) of mTOR, the one responsible for muscle repair and ultimately hypertrophy (growth).

You will find some studies supporting the use of Phosphatidic Acid, and I’ve put a couple of links at the end of the article. The one companies are currently shouting about is: Phosphatidic acid enhances mTOR signaling and resistance exercise induced hypertrophy where subjects gained twice as much lean muscle mass and lost more than twice as much body fat as the placebo group.

Reliability of Studies

This is merely conjecture on my part, but many of the lead scientists in these studies – and indeed the laboratories they conduct the trials out of – can have pretty close ties to supplement companies. I’m not suggesting anything untoward happens, but there are ways in which a study’s findings can sway more favourably in the direction of the desired result.

No doubt they will sell many many bottles of Phosphatidic Acid-based supplements in the months and possibly years to come, but try to remember that real muscle gain starts with nutrition, exercise and adequate rest. Without looking after those aspects of your life, all the supplements in the world won’t make you pile on the muscle.

Supplement Examples

Max Muscle – MaxxTOR
Fuel: One – Phospha Build (click for our review)
Cutler Nutrition – Cutler KING (click for our review)
EPIQ Results – Phosphatidic Acid


HGH MusclesIt’s been known for centuries that lifting heavy loads induces a growth response from our muscles. More precise details on the nature of how this works – including the mTOR pathways used – have only been discovered in recent years.

Clinical studies can show the effect of supplements on this system, measured against a placebo group. The results are there for all to see. How you interpret the results is up to you, but the supplement companies will want you to accept them whole-heartedly, whereas some people will tell you the science is completely rigged. I’m somewhere in the middle, and I believe supplements work as part of a broader spectrum of general health mixed with a goal oriented training schedule.

Adding supplementation to that basic formula of eat, exercise and sleep is extremely useful, but look after the basics first and make sure your supplement is just that; a supplement.

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Phosphatidic Acid Supporting Studies

Wilson, JM et al – Phosphatidic acid enhances mTOR signaling and resistance exercise induced hypertrophy – 2014

Hoffman, JR et al – Efficacy of phosphatidic acid ingestion on lean body mass, muscle thickness and strength gains in resistance-trained men – 2012