Akshay is right in a way. Acting is fake at the end of the day no matter how much importance you give it. You are creating a fake world and it's okay to use other fake things to get your point across. Sorry but you don't need to sit at home for 6 months getting fat for a role. You can use a fat suit and make-up. You don't need to wait for a year to grow your hair when wigs and extensions are available. If you need to really take drugs to play a drug-addicted character, maybe you're just not that great an actor.
It's good to prepare and make things look authentic but there should be a limit to everything. If you're making a story about climbing Mt. Everest, you don't need to learn mountain climbing for two years. You can use a stunt double, it's fine!
As for art, BW is not art. Most commercial movies the mainstream actors do are just packages made to earn money. They just use the "method acting" schtick for PR to prove how serious and talented they are. Really, how funny is it that Aamir probably sat at home for 6 months growing a beard for Lal Singh Chadha and will use it for PR when he promotes...except that the scenes are ultimately just a copy of Forest Gump. Ranveer's performance he apparently locked himself in a room for very obviously inspired by Khal Drogo. So what does it matter?
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