Kevin Smith has dropped 51lbs since his heart attack six months ago.

The 48-year-old director - who previously lost 90lbs in seven years - took to Instagram on Sunday (26.08.18) to share a before and after shot of his transformation since undergoing emergency surgery and after becoming an ambassador for Weight Watchers.

The filmmaker has been on a plant-based only diet, and his weight loss is largely thanks to Penn Jillette's book 'Presto!', which chronicled his 100lb weight loss, and advice from dietary nutrition researcher Ray Cronise.

Despite his impressive progress, Kevin says he still wants to lose another 10lbs.

Revealing how he's shed the pounds, he wrote in a lengthy post on the social media app: ''This @weightwatchers Ambassador is thrilled to announce that I'VE LOST 51 POUNDS! Six months ago from right now, I was in the hospital recovering from a heart attack I'd had the night before. When I went to my Doctor a week later, she told me ''The best thing you can do for yourself now is to lose 50 pounds.'' Half a year later, I can report that I followed Doctor's orders: I started at 256 and now I weigh 205. This is the lightest I've been since high school! My hope now is I can slowly lose another 10 with #weightwatchers and get down to my birth weight of 195! But for now, I'm ecstatic to have reached this chunky milestone! I wanna thank #pennjillette for his book #presto, @raycronise for getting me started with his potato famine, and the good folks at #weightwatchers for their app-based program that made it easy to keep track of and control my eating! And I also wanna thank my kid @harleyquinnsmith - the little vegan astronaut who explored this meatless/milkless galaxy ahead of me, leading by example. Since I never wanted to see the inside of a hospital ever again, I simply copied the Kid. So this wasn't a diet: these results came from a total lifestyle change of eating solely plant-based foods (which is tough because I hate vegetables). But mostly, I wanna thank all of you as well - for the kind and encouraging words along the way. Never underestimate the power of positive feedback: you folks telling me I looked better or healthier helped me stick with it. An encouraging word can really make a difference in someone's life and your compliments kept me going! And just look where I went! #KevinSmith #WWambassador #WWFreestyle #WWFamily #WWBros #weightlosstransformation #weightloss #WWCommunity #ad *People following the Weight Watchers program can expect to lose 1-2lbs per week. (sic)''

Kevin previously dubbed his widow-maker heart attack as the ''best thing'' that has ever happened to his health.

He said earlier this year: ''Down 26 pounds today! Started March 8th and now 4 weeks later, I've lost a small child worth of weight! Doc told me to lose 50 pounds and I'm now over halfway to that goal! Ironically, this heart attack was the best thing that ever happened to my health! (sic)''