EXCLUSIVE: James Franco Says He 'Ate Salads for a Year' to Prep for 'The Deuce' & 'Disaster Artist' Sex Scenes

The star opened up to ET about how he ate healthy to keep fit for his recent slew of steamy scenes and super-tight costumes.

Between his new movie The Disaster Artist -- which recounts the making of the iconicly bad film The Room --  and the upcoming HBO series The Deuce -- set in the gritty, filthy streets of New York City in the 1970s -- James Franco has had quite a few sex scenes to shoot in recent months, and the actor says he had to find a way to keep fit and slim.

ET's Leanne Aguilera caught up with Franco at the premiere of The Deuce in NYC on Thursday, where he opened up about his particular dietary regime to stay sex scene-ready and to fit into the very tight styles of the '70s.

"I ate a lot of salads. Like, a year and a half of salads for lunch and dinner," Franco said, explaining that his nutrition plan wasn't just for his role in The Deuce, but also for when he starred as notorious filmmaker Tommy Wiseau in The Disaster Artist. "Speaking of sex scenes, he has some infamous sex scenes."

"[Wiseau is] unnaturally cut [and] he's incredibly pale. He looks like a muscular corpse," Franco explained. "But I had to depict the making of those scenes, so I started the salads for that and then it just rolled into this and I was like, 'All right, I'll keep it up for the 70's clothes.'"

As for The Deuce, Franco wasn't just acting in the sex scenes. For two episodes in the first season, he also served as the director -- and according to the 39-year-old star, everyone treats those scenes with more respect and dignity than most would believe.

"The truth is, you want to be really professional in those things," Franco shared. "No goofy rituals, it's [just] business, everybody up front and honest with each other."

In The Deuce, created by David Simon and his frequent collaborator, George Pelecanos, Franco plays two identical twin brothers who get wrapped up with the mob, the police and the city's burgeoning pornography industry.

Maggie Gyllenhaal also stars in the gritty period piece as Eileen "Candy" Merrell, a prostitute who works out of Times Square and, thanks to her keen eye for financial opportunities, also gets involved in the quickly booming porn business.

Both Franco and Gyllenhaal serve as executive producers on the new series, and Franco had nothing but praise for his co-star and fellow EP.

"All I gotta say is, Maggie Gyllenhaal is the s**t," Franco declared. "I mean, she is awesome, all around. Everyone knows she's an incredible actress… [but] I think she's going to be the stand-out for this series -- she's so good."

The Deuce premieres Sept. 10 at 9 p.m. ET/PT on HBO. The Disaster Artist hits theaters in limited release on Dec. 1 and opens nationwide on Dec. 8.