Kevin Smith celebrates dramatic weight loss six months after severe heart attack

It's been half a year since Kevin Smith suffered a near-fatal heart attack and was instructed by his doctor to lose quite a lot of weight. Now, the acclaimed director is celebrating a job well done.

Smith took to Instagram on Sunday to show yet again how much he likes going above and beyond people's expectations with a front and side shot of his incredible progress.

Kevin Smith Reflects on Near Fatal Heart Attack While Celebrating 48th Birthday

"This @weightwatchers Ambassador is thrilled to announce that I’VE LOST 51 POUNDS!" he declared.

"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," Smith wrote. "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!" Smith joked. "But for now, I’m ecstatic to have reached this chunky milestone!"

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Smith went on to thank Penn Jillette -- who recently documented his own massive weight loss in his book Presto! -- and radical nutritionist Ray Cronise for their sage dieting wisdom, as well as his daughter, for leading him to and supporting his new vegan lifestyle.

"Mostly, I wanna thank all of you as well - for the kind and encouraging words along the way," Smith added. "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!"

Smith was rushed to the hospital on Feb. 25 with a 100% blockage of his left anterior descending artery, which is also known as a "widow-maker." However, due to emergency surgery and talented doctors, Smith survived.

Kevin Smith Says Heart Attack Was 'Ironically' Best Thing for His Health While Revealing Latest Weight Loss

Smith had already lost 80-90 pounds over the decade leading up to his cardiac episode, but doctors said the damage had already been done and he needed to get even healthier, which lead to his aggressive approach to weight loss and changing his relationship with food.

ET caught up with Smith at San Diego Comic-Con last month, and the "Hollyweed" star admitted that he never thought he would ever actually be fit.

"I just assumed I'd be fat my whole life and I'd never see my high school weight again or any of those things," Smith shared. "But after the heart attack, suddenly I was like, all right, I never want to be back in that room again with someone going up my groin to get to my heart through my femoral artery, telling me that there is a 20 percent chance that I will live, and 80 percent chance I'll die."

Check out the video below to hear more from Smith about his new, healthier lifestyle, and how his brush with death motivated him to resurrect "Hollyweed," an old comedy project that he'd made years ago and is now trying to bring to TV.