The actor joked his Marvel co-star needs to 'put on 25 pound real quick.'
"Cheat day today. Decided to treat myself to this extra large donut, gush it's heavy," Hemsworth quipped in the caption.
Pratt, who will appear in Thor: Love and Thunder as Star-Lord alongside Hemsworth who plays Thor, took to the comments section, writing, "Just heard from my trainer and he needs you to stop working out."
"Since we're gonna be in the same movie and everything he doesn't want me to stand next to you if you look like that," Pratt quipped. "So I'm gonna need you to put on 25 pounds real quick. Cool, thanks."
Hemsworth laughed off Pratt's suggestion, joking that an Instagram filter was actually responsible for his fit physique.
"Don't worry mate. We can just both use the same fancy filter that's been applied here. It's called InstaShred," Hemsworth wrote.
Watch the video below for more on Hemsworth's workouts.