I am 37 years old male, recently went on the keto diet for 3 months and lost ~13 kg (but still have a way to go), to sustain the gains I started working out to gain more muscles and increase my passive metabolic rate.
This paper states that keto is good to maintain existing muscles, however, for maximum muscle gain, one needs cortisol and insulin, which are both being depleted by lack of carbs.
If I would use protein (whey powder isolate + daily protein intake from diet) of 2g per kg of lean mass and stick to intermittent fasting (14hr, 10pm - 2pm) until an hour before exercise, and then continue on keto (~50g carb per day), how big of an effect on reduced muscle growth I could expect? Are we talking half the growth or something like 10% muscle gain reduction? I understand that it's not a perfect science, still, a ballpark figure should be possible.