Jack Osbourne is not holding back. The reality star just unleashed on what he calls 'f***ing insane' trolls, targeting him for being 'grossly underweight.' Osbourne, 38, is slamming online critics, attributing his significant slimdown to rigorous fitness training and a sober lifestyle. He's previously spoken openly about abstaining from drugs and alcohol. Now, he's making it clear: his health journey is his own, and he's had enough of the baseless speculation.