Honestly, I don't see any reason the media has to be responsible for modeling lifestyle or size. Sure, it'd be nice but why on earth do we expect that of them?
There have been some amazing overweight actors through the years. If we judged all actors firstly on size and secondly on other attributes we'd be missing folks like WC Fields, Peter Ustinov, Orson Welles, John Belushi, Jackie Gleason, Marlin Brando, Dom Deluise, Lou Costello and more. It's much harder to put together a list of overweight actresses, which makes me wonder what kind of talent we've missed out on enjoying over the years. A few actresses that are relatively unknown but were brilliant in their own way, despite being far from a physical ideal are Josephine Hull (Arsenic and Old Lace, Harvey) and Margaret Dumont (pretty much any Marx Bros movie ever made). Both fabulous comedic actresses in their day, neither physically appealing, but they brought an amazing talent to the screen even if they always played supporting roles.