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The effects of a Keto diet on muscle building.

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What are the effects of a keto diet on muscle building? Muscles accommodate approximately 40% of our body and it is the muscle plasticity that is the essential feature of what makes the tissue react to different stimuli. For example, growing muscle mass in response to resistance training. Muscle fibers are designed in a way to ensure a balance between muscle loss (catabolism) and muscle growth (anabolism), nutrition and exercise are two factors that intervene and influence this balance.  

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What is a ketogenic diet? 

Ketogenic diet, also known as the keto diet, is a low protein, very-low carbohydrate and very high fat-content diet. The purpose of this diet is to make your body a fat burning machine. Normally, your body will use glucose from carbohydrates to fuel your daily activities and exercise. However, the keto diet is based on very low carbohydrates so your body is forced to use your body’s fat sources as fuel as it enters into the state of ketosis. The state of ketosis refers to the moment your body starts to use ketones for functioning instead of glucose from carbohydrates.  You can find more information on the ketogenic diet and how to do it in this post.

How does the ketogenic diet affect muscle mass? 

The current investigations into the link between a ketogenic diet and muscle mass can be a little conflicting.  Let’s go over some studies and see what we can determine.  

One study conducted by WIlson et al (2017) examined the effects of a ketogenic diet on muscle growth and lean body mass maintenance over 11 weeks. 25 participants were randomised between 2 groups, 1 group was placed on a ketogenic diet and another ate a traditional carb-full diet. From week 0-10 the male participants were assigned a ketogenic diet and at week 10-11, carbohydrates were reintroduced back into their diets. During weeks 0-10 (Keto dieting) the study reported: 

  • no significant increase in muscle mass compared to the group on a traditional diet. 
  • both groups lost the same amount of fat and gained roughly the same amount of strength and power.  
  • Increase in testosterone levels  

Whereas in week 10-11 (carbohydrate reintroduction), the study reported: 

  • The keto group gained some weight back  
  • The keto group experiences muscle mass increase  

This study is great for showing how a ketogenic diet may manipulate the testosterone levels which should work in favour of growing muscle mass since the more testosterone a man has, the more power he can exert and hence grow muscle mass quicker. However, this study has shown an increase to testosterone levels but no increase in muscle mass, so we believe the ketogenic diet has limited the muscle growth potential.  

More Ketogenic diet cases studies

Another study conducted by Vargas et al (2018) investigated into the correlation between a ketogenic diet and muscle mass increase during resistance training whilst being in a caloric surplus. This study included 24 healthy male participants who performed an 8-week resistance training program. Over 8 weeks the study reported:  

  • A great reduction in fat mass  
  • No increase in weight or muscle mass 

So, this study, like the previous study, shows that the participant’s lost fat mass but were unsuccessful in gaining muscle mass.  

Moving forward, another study conducted by Greene et al (2018) examined the effects of a ketogenic diet on power lifters. This study included 14 power lifters and it was found that the power lifters lost lean body mass but somehow managed to maintain their power.  

Likewise, another study conducted by Jabekk et al (2010 and included 18 overweight women. They were randomised into two groups; a ketogenic diet group and a regular diet. Both groups underwent 10 weeks of resistance training. The study demonstrated: 

  • The ketogenic group maintained lean body mass whilst losing body fat 
  • The regular diet group increased lean body mass without significantly losing body fat 

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Considering all these studies, it is fair to conclude that a ketogenic diet doesn’t really affect the muscle mass, it seems to limit its growth but it is muscle sparing. All those studies have one thing in common, participants were able to maintain their muscle mass but failed to grow their muscle mass even in a caloric surplus. So, a ketogenic diet seems to have muscle protective effects rather than muscle growing properties.   

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Greene, D., Varley, B., Hartwig, T., Chapman, P. and Rigney, M. (2018). A Low-Carbohydrate Ketogenic Diet Reduces Body Mass Without Compromising Performance in Powerlifting and Olympic Weightlifting Athletes. [online] 32(12). Available at: [Accessed 9 Oct. 2019]. 

Jabekk, P., Moe, I., Meen, H., Tomten, S. and Hostmark, A. (2010). Resistance training in overweight women on a ketogenic diet conserved lean body mass while reducing body fat. [online] Available at: [Accessed 9 Oct. 2019]. 

Paoli, A., Pancellara, P., Pompei, P. and Moro, T. (2019). Ketogenic Diet and Skeletal Muscle Hypertrophy: A Frenemy Relationship?. [online] pp.233-247. Available at: [Accessed 9 Oct. 2019]. 

Vargas, S., Romance, R., Petro, J., Bonilla, D., Galancho, I., Espinar, S., Kreider, R. and Bonitez-Porrez, J. (2018). Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial. [online] 15(1). Available at: [Accessed 9 Oct. 2019]. 

Wilson, J., Lowery, R., Roberts, M., Sharp, M., Joy, J., Shields, K., Partl, J., Volek, J. and D’Agostino, D. (2017). The Effects of Ketogenic Dieting on Body Composition, Strength, Power, and Hormonal Profiles in Resistance Training Males. [online] Available at: [Accessed 10 Oct. 2019]. 


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