how much of a calorific surplus do you need to gain muscle with minimal fat
You do not need to be in a surplus.
You need the stimulus (training) and then to be able to feed that with amino acids.
So you need enough macronutrients and calories that your body isn’t cannabalizing muscle tissue/the protein that you eat for energy requirements. Thats it.
Clearly, it’s more complex that this but until someone is very lean (sub 10%) it’s more than possible to gain muscle and lose fat at the same time. Whether that is a bit much of a competing priority for optimal progress is beyond the scope of this medium.
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