David Harbour Shares Pics from Dramatic Stranger Things Weight Loss Journey

On Thursday, the actor who stunned audiences with his stunning body transformation, opened up about the experience of losing 75-80 pounds between seasons, and why he's now struggling to lose again.

Within the context of the story, Hopper has spent the time between Seasons 3 and 4 in a Russian prison suffering plenty of hard work, cruelty and a definite lack of well-balanced meals. In real life, it was up to Harbour.

Sharing a series of images of his weight-loss journey to his Instagram, Harbour praised the hard work of his trainer David Higgins over eight months as he went from "265-270" "all the way down to 190" when they shot the new season.

To make matters even more challenging for the actor, he shared that after all of the blood, sweat and tears needed to shed those 75 pounds, he then had to hold that weight for an extra year thanks to pandemic-related production delays.

Unfortunately, despite learning a healthier lifestyle, Harbour quickly found out that he needed to unlearn it. "Recently ballooned up again to play jolly ole st. Nick in a flick I can’t wait for you to see this holiday season," the actor said, teasing his upcoming film "Violent Night."

He then revealed that he's now "struggling to fight back down towards a good weight for wherever hopper ends up in season 5." Once again, he's putting his body through it for the work that he's doing as an actor.

And while he's not the first to put their body through extreme and rapid weight changes for the craft, the 47 year old actor acknowledges "All this up and down is not good for the body, and I’ll have to give it up soon."

At the same time, he noted that "it is such a fun part of the job to live in a different version of your skin for a while."

In a recent interview with British GQ, Harbour insisted he wouldn't do this kind of weight loss or gain again, laughing that prosthetics have come too far and are too good. For early scenes of Hopper in the prison, they used prosthetics to mimic how he looked prior to his weight loss.

Harbour is planning an Instagram Live session for 11 a.m. ET on Friday to answer any questions and share what he learned on his journey.

The good news is he appears to have some time before he needs to land on whatever Hopper's Season 5 weight is going to be as production for the final season of "Stranger Things" is not even set yet.