Body builders eat protein shakes and all kinds of ridiculous supplements and weight train, let muscles rest, then resume weight training.
Point me towards lumberjacks that eat primarily a fish based diet and have significantly increased muscle mass. I call bovine feces.
Working everyday fishing and farming(and raiding in the Summer) from sun up to sun down while eating a fish based diet does not lead to significantly increasing muscle mass.
Well head up to north eastern Canada. You’ll be deluged in something that isn’t bovine feces. Head to the Pacific NW and you’ll find more. They eat fish and meat just like all cultures always have. Heavy on the fish being both are costal.
Big. Big boys.
And there are plenty of athletes not indebted to GNC for their diet. I don’t know how this is news to you. Lots of them simply eat specific diets and skip the science.