If a man suffers from E.D for an extended period of time he will lose size. Without erections to keep the penis healthy scar tissue can develop and the erect penis will be shorter as a result. As long as a man is having regular erections I don't think he loses size. Gaining weight or developing a fat pad will make it appear shorter than a slim man but the dick is still the same length but part of it is not visible. Like someone above mentioned girth can increase with age. Mine did