The actor was spotted on the set of The Gambler in Los Angeles looking thinner than we've ever seen him before!
The 41-year-old recently opened up about his weight loss goals to Extra, saying, "I'm trying to get as thin as I possibly can. I'm playing a literary professor who also has some serious addiction problems, trying to get ready for that."
He admitted that he's already dropped 40 pounds and is trying to maintain his weight at around 150 pounds.
Losing the weight hasn't been easy for Walhberg though.
He joked that he was tempted to "rob" his daughter for her breakfast pastry one morning.
"It's getting bad," he said while laughing.
The hunky actor is just the latest in a long list of stars that have undergone serious weight loss transformations for a film role.
Matthew McConaughey famously shed a shocking 38 pounds to play Rob Woodroof in the Dallas Buyers Club.
Jared Leto also lost a significant amount of body fat, and looked like a shadow of his former self, to play a transsexual with AIDS in the award-winning movie.