Jack Osbourne is not holding back. The reality star just unleashed on online trolls who labeled him 'grossly underweight.' Osbourne, 38, took to social media, shutting down critics and revealing his ongoing health struggles. He's been living with multiple sclerosis for over a decade. This isn't just about appearance, it's about a man fighting a chronic illness. His message to the haters: understand before you judge. We're monitoring the fallout from this very public confrontation.