I have read so much about diets that warning that not eating adequate amounts of protein will result in muscle loss. On the other hand I see people like Christian Bale almost flaunting this rule going up and down the built_rake-thin scale multiple times successfully.
Is it true that muscles lost is lost forever ? If so how do people like him do it ? When I see him in the Machinist I don't think his frame just shows water loss from muscles only right ?