"The magic recipe of gaining muscle mass up to 1-2 kilo's in a few weeks and no fat is purely fictional and should be disregarded."
If it existed, you could market it and make millions.
You can do it artificially to a degree, but then it becomes an issue of health.
High protein diets are not particularly great for the GI tract or renal system. Eating excessive meat in general is not great for the GI tract. Supplementing with whey protein is generally low risk, but add creatine to the mix for faster results and you run the risk of maintaining a body water percentage below what is healthy. Guys on creatine can keel over during intensive long duration endurance exercises (like ruck marching). Other supplements up to but not including steroids work to various degrees, but there are no magic "muscle builders in a bottle."
I'm not even going to go into the topic of steroid use beyond say that they work well, and that they do so at a heavy price with prolonged use.
With a specifically tailored MS regimen and tailored diet, it is very possible to put on only lean mass, but people generally pay thousands for this type of individual training and coaching.
