Building Muscle on Keto

9 min read

Gaining muscle mass can be a challenging task for many. A regular exercise routine, carefully planned nutrition, and lots of discipline are just a few things that come to mind when this topic is being brought up. Indeed, managing these aspects of your lifestyle requires serious determination. Adding the keto diet to this equation can seem like another barrier to achieving your goals. Besides, many people argue that turning to a diet limiting your carb intake is the exact opposite of what athletes and bodybuilders do to gain muscle. However, does scientific research suggest this is so, or can the keto diet be your friend and help you get the gains more rapidly? Today we will aim to delve deeper into the mechanisms of how muscle is built and address this exact question from a physiological perspective.

Mechanisms of Muscle Synthesis

To start off, we need to understand how the human body produces new muscle tissue. This can be best described as constant interplay between two simultaneous processes: muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In a nutshell, most new muscle cells are built from amino acids recycled by MPB from existing muscle tissue. In contrast, dietary amino acids only comprise 20% of MPS under normal conditions. Therefore, in order to ensure a positive net protein balance (NPB), which will allow new muscle to be formed, MPS has to exceed MPB. Let’s consider both processes in more detail to see how this can be achieved.

MPS has its origins in the activity of the mechanistic target of rapamycin (mTOR). This receptor is a sensor to several metabolic parameters and acts as the driving force for MPS. These include hormones, such as insulin and insulin-like growth factor 1 (IGF-1), increased amino acid supply, and mechanical stimuli, like resistance exercise. In their presence, mTOR stimulates MPS, and therefore, leads to the production of new muscle cells. 

MPB on the other hand is a more complex process and unlike MPS, involves multiple pathways. These are less studied but are known to work in tandem and differ based on the size of the muscle cell they are breaking down. The key factors affecting MPB are metabolic amino acid requirement, stress, and fasting, all of which promote MPB if they are increased.

As you may have noticed, both MPS and MPB rely heavily on the availability and demand for amino acids. This seems logical, as amino acids are the building blocks of every protein your body makes, including muscle. We thus arrive at the hypothesis that increasing the supply of amino acids will lead to a rise in MPS and allow you to gain muscle tissue, and this is exactly what current research is pointing towards. More specifically, amino acids like leucine were shown to directly affect the mTOR pathway when ingested orally. Dubbed as the “leucine trigger”, the said phenomenon was recorded in individuals consuming isolated sources of leucine. The effects of the leucine concentration in their bloodstream were directly proportional to the extent of MPS after exercising.

Are carbohydrates essential to build muscle?

Despite this, some people claim that protein alone is not sufficient to increase muscle mass and that carbohydrates are essential for the process. Coming back to the mechanisms of MPS, we can see that the main molecular pathway, i.e., mTOR is indeed stimulated by insulin and IGF-1, which are produced by the body in response to carbohydrate intake.

So, does this make carbohydrates an absolute must when muscle gain is in question? Not exactly.

Yes, their effect on MPS is undeniable, and it will enable you to make more muscle. Still, the critical factor here is the comparison to other factors affecting MPS that we discussed. Studies comparing effects of dietary protein alone and with carbohydrates after exercise all showed increases in both MPS and MPB, however, the difference in muscle growth was insignificant between the supplementation regimens. This finding is crucial as it indicates that exercise is a far more accurate predictor of muscle gain than nutrition and undermines the argument that carbohydrates are necessary to achieve muscle gain.

Another common misconception is that the shortage of glycogen that comes with the cessation of carbohydrate intake will negatively affect your exercise tolerance.

Let’s take this claim apart:
Glycogen is a glucose storage your muscles utilize as a rapid energy source when required. The notion that glycogen impacts athlete performance has existed for half a century, as fatigue and decline in exercise tolerance were found to be proportional to the decline in muscle glycogen in the late 1960s. Consequently, a paradigm has developed, which considers carbohydrate-rich diets the most optimal diet for maintaining exercise performance and recovery. However, subsequent research involving ketogenic diets has shed more light on glycogen’s importance in muscle activity. More specifically, studies have shown that athletes who were adapted to a low-carb ketogenic diet had same levels of muscle glycogen as those consuming a 60% carbohydrate diet, without any of the negative symptoms.

The reason? The fat oxidation was 2.3 higher in athletes on the keto diet, suggesting that they could effectively synthesize glycogen through gluconeogenesis.

This means that after adaptation to the ketogenic diet, i.e., using fat as a primary energy source, your body is able to utilize it for the production of glycogen without the need for carbohydrates. Therefore, the reliance on carbohydrates to make glycogen is evidently not the only dietary intervention that achieves this outcome. However, it must be said that you may feel the symptoms of glycogen shortage in the first week of starting a ketogenic diet, so make sure to check out our article here that describes ways in which you can successfully overcome them.

As for this article, it is time to see what the research on keto-diets has to say about their ability to aid muscle growth.

What the research says:

It is no secret that ketogenic diets are highly effective in promoting weight loss and achieving it quicker and more effectively than other diets. When it comes to direct effects of the traditional ketogenic diet on muscle composition, however, the first thought of many keto-enthusiasts is whether this is due to the loss of muscle tissue, rather than fat. Reassuringly, that is not the case, and scientific evidence suggests otherwise. Firstly, a 12-month-long exposure to a ketogenic diet in mice significantly slowed down an age-related decrease in grip strength, indicative of preservation of muscle tissue. Interestingly, the same study also reported that ketogenic diet prolonged lifespan in mice and even decreased tumor formation, however, this is beyond the scope of this article.

As for human-based research, findings also point towards the effective preservation of muscle tissue over time. This has been the case across multiple studies performed on the efficacy of the ketogenic diet compared to a low-fat diet with weight loss as the primary outcome. Ketogenic diets produced an equal or more significant reduction in lean body mass. They consistently maintained muscle mass, unlike other diets.

In addition, a ketogenic diet has been found to influence the mTOR pathway through its effects on hormone systems and other molecular pathways. Notable examples include increases in testosterone and inhibition of AMPK- an enzyme, which controls protein homeostasis by inhibiting MPS. Coming back to our MPS/MPB infographic, both events will increase mTOR activity in the hypothalamus and, following that, decrease appetite and promote muscle growth.

What research does not say and why it can benefit your keto-journey:

However, all of the mentioned studies have one central point, which must be taken into consideration. Although successfully maintaining muscle mass, the ketogenic diet does not directly provide any means of gaining it. But wait, what about all the effects on the mTOR and hormone systems?

Let’s recall the main determinants of MPS and MPB and their hierarchy.

Firstly, exercise is known to play a far more significant role in mTOR function and muscle gain than any diet, so this will be a key determinant in how much muscle growth you reap. As for amino acid balance and protein intake, the devil is in the details. Studies that found no difference in muscle gain between keto- and other diets assigned equal amounts of protein for both nutrition regimen. Since the exercise routine was also the same for both diet groups, the two primary drivers of MPS were identical. Thus the described outcomes should not come as a surprise. On the brighter side, you can use this knowledge to your advantage and modify your keto diet to maximize your gains. The first tweak is adjusting your protein intake to increase MPS. Traditional keto diets apportion 15% of caloric intake to proteins, which can be brought up by 5-10% given that an appropriate exercise routine is in place, thus increasing the number of available amino acids and a positive NPB. 

However, too much protein is not going to be helpful either, as that could trigger gluconeogenesis, which could kick you out of ketosis.

Speaking of glucose, the second suggestion involves introducing cycles of carbohydrate refeeding. This was highly beneficial for athletes performing high-intensity exercise and, more importantly, improved exercise tolerance and muscle gain in elite race walkers. This is likely due to the activation of the IGF-1-mTOR pathway we discussed earlier, which pairs up with the positive effects of the ketogenic diet on MPS. You can find more information on this version of the keto diet in our “Types of Keto Diet” article.

Final Thoughts:

Building muscle may seem complicated, and rightfully so. Having to manage multiple crucial aspects of diet and lifestyle can be challenging for many of us. However, we hope that this article has provided you with a solid foundation of the mechanisms your body uses to build muscle and how you can modify the ketogenic diet to leverage them. Then, all you have left is to find the version of the keto diet that is right for you and it will be the ke to maximizing your muscle gains. 😉