Mark Wahlberg (Gained 40, Lost 60)
Credit: Everett

Charles Atlas would never understand Wahlberg's reverse body transformation: In 2012, he gained 40 pounds of muscle for Pain and Gain, and earlier this year he got scrawny to play a drug addict in The Gambler. His goal was to go from 197 pounds to "as thin as I possibly can," which ended up being 137 pounds. At one point during the process he admitted, "My daughter was eating a blueberry scone, and I was going to jack her for it."

The Bottom Line:
His daughter – and anyone else he came across – would have been smart to stay out of his way during his extreme diet. "People get irritable and mean when they deprive themselves of calories," says Bacon.