Yes, Smith has been a workout fiend since about his second NFL season. Really hard to imagine that he was around 300lbs at DE in an era where 300 lbs was really big.
photo of him in prime:
https://billswire.usatoday.com/2018/04/07/nfl-com-buffalo-bills-bruce-smith/
link to his rookie card photo
https://www.football-rookies.com/bruce-smith-10833/