Chris Sullivan showed shocking weight loss at the People's Choice Awards after playing obese Toby on NBC's "This Is Us." Sullivan and co-star Chrissy Metz (Kate) portray a couple who meet at Overeaters Anonymous. This show covers their relationship bumps, food addiction, obesity, weight loss struggles, and body image issues. So how does Sullivan, who also stars in Netflix's "Stranger Things," show a much thinner figure in real life? And is weight loss on the script for Metz too?

Chris Sullivan's startling transformation

Weight loss eludes Toby on the popular "This Is Us" but not the real-life actor who plays him.

Sullivan explains his remarkable change enigmatically: actors are chameleons, he says. An actor adapts his appearance to comply with the requirements of the role. Many performers have achieved big weight gain or loss for movies or TV shows. Jared Leto gained 60 pounds for a role, then lost all that plus another 40 pounds to play a transgender HIV patient in "Dallas Buyers Club," and The Joker in "Suicide Squad."

Chrissy Metz, Chris Sullivan lose weight differently

Not all celebrity slimdowns are similar. Jamie Foxx, for example, isn't overweight naturally: he's gained and lost the same 40 pounds for different roles. Some get plastic surgery and then have to artificially "gain back" the weight.

Chris Sullivan, who is much smaller in "Stranger Things" is said to wear a "fat suit" for "This Is Us." Some actors require a total makeover like Melissa McCarthy. The "Mike and Molly" star completely overhauled herself, but her character didn't. She lost so much that she was too thin to play an obese woman, and the show was canceled.

Did Chris Sullivan, Chrissy Metz "have to" slim?

The premise of "This Is Us" showed how weight problems and body image issues impacted Toby and Kate, and their relationship. There was a rumor that Metz appeared at the Golden Globes in a wheelchair because she'd had bariatric surgery. That prompted folks to ask if show producers made her lose weight.

And no, dieting isn't mandatory, but it is in the show trajectory, hinted Metz. The actress is looking forward to it as motivation to shed pounds. As their characters grow smaller, the celebrities who play them will, too.