Smith has lost more than 50lbs over the last year, since ditching animal products on the advice of his doctor, after suffering a massive heart attack in February.
He posted side-by-side images from 2009 and 2019 on Instagram, alongside the caption: "Me, myself & I. #2009vs2019 - thanks to @ww, going Vegan and Runyon hikes. #KevinSmith #wwambassador #ww."
Kevin smith appeared in a PSA for Farm Sanctuary with his daughter
While Smith initially went plant-based for health reasons, over the last year, his daughter Quinn Smith - an ethical vegan - inspired him to take a more compassionate outlook. The pair appeared in a video for the vegan Farm Sanctuary before Thanksgiving last year, urging people to consider not eating turkey.
"I've been a vegan for over six months and there's nothing I miss. You're always told it's OK to eat animals, and that we're supposed to eat animals. And that's just something you're fed. And for a long time, that’s what my generation believed.
"Now we know a lot better...some stuff you just let go...we'll be [eating delicious food and spending time with family this Thanksgiving] but there'll be no carcass on the table...Change happens slow and you have to change the conversation.
"You have my solemn word ladies, I will never eat another turkey. And I will go out of my way to see that others might not as well."