'Stranger Things' star David Harbour shares photos chronicling his 75-pound weight loss for Season 4: 'A difficult and exciting ride'

David Harbour is no stranger to transforming his body.

If there’s one thing Stranger Things fans have noticed in Season 4 of the Netflix series, it’s that Harbour’s beloved character Hopper has lost a significant amount of weight — of course, it’s all explained in the series, which you’ll just have to watch. No spoilers here!

The actor, 47, recently opened up about the process he’s gone through in the last couple years with losing 75 pounds for the latest season then having to gain it all back to play a murderous Santa Claus in the upcoming holiday thriller Violent Night.

“Many of you have asked about Hopper’s physical transformation from season 3 to season 4,” he captioned a series of photos on Instagram.

In the first image, Harbour shares a before and after pic of his slimmed-down character from the third and fourth seasons. In the next photo, he shares a glimpse of the first week when he and his personal trainer, David Higgins, began the process. In the third and final image, Harbour is seen on a shooting day of Stranger Things with black x’s all over his body so video editors can work CGI magic to produce a more "practical effect" of his character's weight loss.

“All told I lost over 75lbs. 265-270 in season 3 and all the way down to 190 when we shot,” the actor continued. “Recently ballooned up again to play jolly ole st. Nick in a flick I can’t wait for you to see this holiday season, so I am struggling to fight back down towards a good weight for wherever hopper ends up in season 5. All this up and down is not good for the body, and I’ll have to give it up soon, but it is such a fun part of the job to live in a different version of your skin for a while.”

The actor’s post received a warm welcome from fans — including from actor and singer Bridget Everett, who wrote, “Very much relate to pic #2 ????.”

“Hopper = hot in any shape. But I love him when he’s built for comfort and not speed,” a fan wrote while another added: “This is amazing! But I hope it won't be stressful for your body.”

“We ?? all versions of Hopper!”

Another added, “Dilf since day one, love u sir.”

Harbour elaborated about his weight loss process in an interview with GQ Hype earlier this month.

When explaining how he was able to lose it all in a matter of eight months, the actor said it came down to rigorous fitness training, intermittent fasting and Pilates. But don't bet on him doing it again anytime soon.

“I don’t think I’ll ever do that again,” he said. “I have this Santa Claus movie coming out for Universal in December and I gained [it all back]. But now, yeah, never again. The prosthetics are too good.”

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