wowed fans on Monday with his impressive transformation, appearing jolly on the black carpet in a vibrant canary tie.At his heaviest, the “Argo” star tipped the scales at 392 pounds but has since shed more than half his body weight after embarking on a fitness journey in 2007.He quit drinking, enlisting the help of a personal trainer, Mackie Shilstone, who pushed him to go the extra mile, adopting a Mediterranean diet and introducing regular exercise into his routine.“People think this is overnight, but most people make a contribution to weight management, but they don’t make a commitment to it,” Shilstone, 72, told The Post on Tuesday.Goodman had lost 85 pounds when he first began his health journey but quickly regained it after Hurricane Katrina struck — until Shilstone stepped in.He took his client for a walk in a cemetery where there was empty land and handed him a shovel.“I said, ‘John, here’s a shovel. You told me you’re going to recommit yourself and follow this plan,’” Shilstone continued.