How much weight did Brad Pitt gain for Troy?

I'm curious to know, during the preparation for his role in the epic film Troy, just how much weight did Brad Pitt put on to embody the physique of the legendary warrior Achilles? It's well known that actors often undergo significant physical transformations for their roles, so I'm eager to find out the specifics of Pitt's journey. Was it a significant amount of muscle mass he gained, or did he focus on a specific type of training to achieve the look? And how did this transformation impact his overall health and fitness during and after the filming process?