The director Geroge Tillman Jr didn't want to use a fat suit or visual effects in order to show the transformation Foreman went through from his prime to when he came out of retirement to return to boxing in his forties. The filming was split into two blocks; first to shoot scenes where Foreman is at his prime and later for when he's in his forties. The crew took six weeks off so Khris Davis could bulk up for the latter part of the filming. Davis had pretty strict instructions on how many calories to eat per day, depending on his training regime, but the actor went above and beyond, consuming 7000 calories a day to gain the necessary weight. He went from 225 to 275 in six weeks eventually ending up at around 282.
When he fought Michael Moorer in Las Vegas, George Foreman wore the same red trunks that he wore in the Rumble in the Jungle in Kinshasa, Zaire (now DR Congo) in 1974. That legendary fight was the climactic scene of Muhammad Ali's biopic Ali (2001) with Will Smith as Ali and Charles Shufford as Foreman and remains Foreman's only loss by knockout. Furthermore, in both the Rumble in the Jungle and Foreman vs. Moorer, the older challenger was trailing the younger and undefeated champion on all of the judges' scorecards late in the fight before winning by knockout. Foreman's victory made him the oldest world heavyweight boxing champion in history at 45 years and 360 days, which beat Jersey Joe Walcott's old record by eight years and is a record that Foreman still holds. Since then, only Vitali Klitschko has been a world heavyweight champion aged 40 or older. Furthermore, Bernard Hopkins and Archie Moore are the only world boxing champions in any weight class at an older age than Foreman was after Hopkins beat Jean Pascal in 2011 for the light heavyweight championships.
In recreating Ali's 8th round knockdown of Foreman in Zaire, had to be filmed about 30 to 40 times in order to get the famous three punch combination correct.
George Foreman has been married four times, but only his first and fourth (and current) marriages are covered in the movie. For some reason, the name of his first wife has been changed from "Adrienne" to "Paula" in the film.