Let’s set this record straight, you absolutely can lose fat eating a keto diet.  The question is, can you also build muscle on it?  Simply put, sure, but it’s not easy nor ideal.  Just like you can walk to school in the morning, but driving will get you there much quicker.  That’s the perfect analogy for hypertrophy on keto.

For hypertrophy’s sake, the intake of carbs and a good prescription of proteins and fats will work best.  This combination gives you the needed fuel for anaerobic output.  It’s also the preferred source of fuel.  On top of that, perfectly times carb intake will help you to consume enough calories in general to promote muscle growth.

If the goal is more muscle mass, let's look at it this way…through SCIENCE!

In a 2018 Journal of the International Society of Sports Nutrition study, the effects of a ketogenic diet on body mass index (BMI) was studied with 24 healthy males over an 8-week period.

All 24 performed resistance training for the 8-week program.  Nine of the 24 were assigned a ketogenic diet, ten were assigned a non-keto diet, the rest (five) were told to eat like they normally do.

What did they find?  The keto group did see a very significant drop in body fat, the other two groups did not.  But, the two non-keto did see an increase in muscle mass…not so much in the keto group.  The researchers concluded that the keto diet was very effective in decreasing body fat without decreasing lean mass, but that it was not effective in gaining lean mass.  So, keto is a no-go for bulking...

(Vargas S et al. Efficacy Of Ketogenic Diet On Body Composition During Resistance Training In Trained Men. J Int Soc Sports Nutr. 2018 Jul 9;15(1):31)