It's impressive that he maintained this lifestyle - though it must have been difficult for those around him, not to mention, rather smelly?
He laughs. "I was by myself the whole time.
"I only ate cans of tuna the whole time. I probably have mercury poisoning now because I ate it just out of the can. That's all that was there: tuna, hot sauce, and Nespresso capsules."
It seems his commitment paid off. At the Cannes Film Festival, where the audiences are tough at the best of times, Pattinson received a standing ovation when the end credits rolled. Quite a departure from his adored role in the Twilight franchise which made him an international celebrity but his acting skills were never taken seriously.
I ask him whether he was surprised by the positive reaction he received towards his performance.
"I am always way more surprised that I am considered a heart throb." He laughs. "That really blows my mind. Before Twilight, I never got the good looking parts, ever. I was gangly," he insists.
"What's weird is that you can do one movie and everything changes. I think that's why I get a lot of weird reactions to me being in movies. You have someone's face [associated with a beloved fictional role] and then people were so obsessed with that character.
"In Twilight they were like, 'You are so beautiful.' Literally, the amount of times that I've been walking down the street, looking disgusting, and then someone who is a Twilight fan would say, 'You're so beautiful!' And [I wanted to say], 'You are literally, actually not seeing reality,'" he says.
"And there are other people who got furious over it, saying, 'What are you talking about? He's ugly!'" He sighs. "So stupid!" He looks at the ground, shakes his head and says, "I can't believe I just talked about that."
Pattinson must have felt validated at the reaction he received on opening night at the glamorous festival. "It was crazy. People were crying. And this movie specifically was such a long shot. I am really proud of it. It's a really nice feeling."
Robert Pattinson with Good Time director Benny Safdie (left), and director Josh Safdie. Picture: AP Photo/James McCauley
Robert Pattinson with Good Time director Benny Safdie (left), and director Josh Safdie. Picture: AP Photo/James McCauleySource:AP
He's hoping Good Time will change his perception in Hollywood. "Doing a role like this allows you more freedom on the next job. Hopefully people will think, 'I want to take a risk on him.' Before it was like, 'Everyone thinks you are sh*t,' and the director would be like, 'No. No one would believe you in that kind of role.' But if you have proven yourself a few times people will say, 'Yeah, maybe we will go with him. Hopefully it will work out'," he says, shrugging his shoulders. "But of course there are no guarantees."
Times have changed since he had paparazzi following his every move. "I really don't have to think about the fans [anymore]. I live in London where it's not really a thing. And also, over the last few years, just the nature of fame has changed so much.
"I noticed even in LA, there's hardly any paparazzi anymore because people take their own photos on Instagram. Nobody buys gossip magazines because everybody just looks on the internet," he says.
"So, if there's no money in it, no one does it anymore. It's great." He grins. "In LA, there were areas where I would never dream of going to, like certain shopping streets. Five years ago, there would be 30 paparazzi on every street. I am just getting used to that and it's so nice to let that fear of being spied on go away."
The last time we spoke was for his Dior commercial when he became the spokesman for the luxe brand. "Yeah, it's funny. I remember signing up with Dior and I was so nervous about it because a few years ago when I decided to do it there weren't that many actors doing that kind of thing on that level. They might do it in Japan or somewhere where they thought they wouldn't get noticed. Otherwise, they wouldn't be taken seriously as an actor."
But they dangled the carrot and Pattinson couldn't resist. "They gave me final cut on the commercial." He smiles. "Then the next year, literally every single actor in the world was doing one. So, it's not really a moral conundrum anymore."
It seems his second job pays well. "Yes, it does. I am basically a model, that's my other job."