David Harbour says he's 'struggling' to get back to a good weight after losing 75 pounds for 'Stranger Things' and gaining some back for another movie

• David Harbour, 47, stars as Jim Hopper in Netflix's hit series "Stranger Things."
• In an Instagram post, the actor said he worked with a trainer for eight months to lose 75 pounds.

Actor David Harbour responded to fans who had been asking about "Hopper's physical transformation" between seasons three and four.

Harbour, who plays Hawkins police chief Jim Hopper, had previously said he lost around 80 pounds for the Netflix series.

In the caption of an Instagram post shared Thursday afternoon, Harbour said he worked with a personal trainer for eight months "to make the transformation, and then another year to keep it through the pandemic."

"All told it was a difficult and exciting ride, changing diet and exercise plans (or lack thereof)," Harbour wrote in the caption of several images before and after the training.

"Stranger Things" season four picks up in March 1986 — about eight months after the Battle at Starcourt in the season three finale. As the show reveals, Hopper spent that time being tortured by Russian government officials in remote prison facilities.

The fourth season finale included a scene between Hopper and Joyce where she sees him shirtless. Hopper is not only dramatically underweight but he's covered in scars.

On Instagram, Harbour posted a mirror selfie from "shoot day" of the finale episode.

"The black x's are for cgi scarring because of problems with the practical effect," Harbour said.

The 47-year-old actor lost over 75 pounds, bringing him from about 270 pounds in season three down to "190 when we shot," according to his Instagram.

"Recently ballooned up again to play jolly ole St. Nick in a flick I can't wait for you to see this holiday season," Harbour said. "So I am struggling to fight back down towards a good weight for wherever Hopper ends up in season five."

He continued: "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."

Last month, Harbour also said the weight loss meant he needed facial prosthetics to film Hopper's flashback scenes. The actor told cocreators, Matt and Ross Duffer, that they should shoot any flashbacks right at the end of season three's filming period. But the scenes hadn't been written yet, so Harbour had fake cheeks applied in order to film the scene where we see how Hopper was captured by the Russian government.

There's a long history of Hollywood actors either gaining weight or losing it for various movies and TV shows.

Sometimes it's so the actors can show a plot-related change to their physical appearance during different periods of time in the same story, like Tom Hanks losing 55 pounds to play a marooned man in "Castaway."

Other times it's to make themselves appear more physically like a real person their character is based on for the duration of a movie, like Hilary Swank bulking up 19 pounds of muscle to play a boxer.

Some celebrities, like Jonah Hill, have been vocal about receiving unwanted attention for their physical transformations.

"I know you mean well but I kindly ask that you not comment on my body," the "Superbad" actor wrote on Instagram in October 2021. "Good or bad I want to politely let you know it's not helpful and doesn't feel good. Much respect."

For more about "Stranger Things," read more about 19 behind-the-scenes secrets you probably might not have known about season four.