Linemen are bigtime athletes, often with fast metabolisms, and have to eat and supplement to the point of discomfort to maintain their 300lb+ playing weight. Joe Thomas, Alan Faneca and Craig Terrill look like completely different people now that they can eat less/cleaner.
And then you look at some guys who were in great shape while playing - Jones-Drew, Marshall Faulk - kind of the opposite.
And for a lot of guys, post-college or the pros, there is a overall relief to be able to stop the PEDs without worrying about performance outcomes anymore.