Are you implying that as you get more muscular, your dick will shrink or something? I dont think that even remotely makes sense.
I think BigDallasDick8x6 made a pretty good point.
maybe the hormons go or in the muscles or the penis.
There could be a correlation between fat built people and smaller dicks, but i dont see how lifechoices later on, may affect your penis growth. (Besides artificial enhancement)