But Berg, who has teamed up with Wahlberg on five occasions, wanted the 48-year-old "ripped for the role."
"I said, 'OK, no problem,'" Wahlberg remembered.
"I literally went clean-dry for five months, trained like a crazy person. I just did a bone broth and a fast and a cleanse and I literally lost 10 pounds [4.5kg] in five days. I lost five per cent body fat and I lost 20 points [9kg] of visceral fat literally in five days.
"Just bone broth and then steamed vegetables after the first three days and then a little bit of protein at night and that was it."
Wahlberg has previously credited Aussie fitness chain F45 for staying in shape, suggesting he's a huge fan of efficiency when working out.
“I’m very precious with my time, which is why I’m so disciplined,” he told us at the time.
“I try to inspire people that there is enough time in the day to accomplish all of your goals and find that great balance.”