‘I probably shouldn’t do this again’: Joaquin Phoenix and Lady Gaga talk about ‘difficult’ Joker diets

Joaquin Phoenix and Lady Gaga discussed the punishing diets each undertook for the Joker sequel, ahead of the film’s premiere at the Venice film festival.

At a press conference alongside the film’s writer-director, Todd Phillips, Phoenix talked about the pre-production regime he revisited, having lost 52lb – a little under 4 stone, or about 24kg – by eating mostly lettuce and steamed vegetables for the original.

“It’s not really that dangerous,” said Phoenix, adding that they worked “with a doctor” but that eating frugally inevitably “becomes your obsession”.

“I’m not going to talk through specifics of the diet,” he continued, “but this time it felt a bit more complicated just because there was so much dance rehearsal that we were doing, which I didn’t have last time.

“So it felt a bit more difficult, but it is safe. But I’m now 49, I probably shouldn’t do this again. This is probably it for me.”

The first Joker, in which Phoenix plays aspiring standup comedian Arthur Fleck, won the Golden Lion at Venice in 2019 and the best actor Oscar for Phoenix the following year – as well as 11 Academy Award nominations.

He is joined by Lady Gaga for the follow-up, in which their characters meet during a music therapy class he has been permitted to attend while in prison. Gaga also lost a large amount of weight for the role, said Phoenix, addressing her in the press conference.

“I remember when I first met you in rehearsals and then you went away and then when you came back, you lost a lot of weight. It was really impressive.”

Gaga said: “I think we transformed into our characters over time and continued to hone every kind of detail.” She added that “We fed [Phoenix] blueberries when he was really hungry.”

Phoenix was also asked about his dropping out of Todd Haynes’s untitled gay romance film five days before it was set to begin filming in Mexico, but declined to answer, saying: “If I do, I’d just be sharing my opinion from my perspective and the other creatives aren’t here to say their piece,” said Phoenix, “and so I don’t think that would be helpful.”

The move raised eyebrows last month as Phoenix and his collaborators had taken the project to Haynes and his longtime producer Christine Vachon.

Joker: Folie à Deux is one of the autumn’s most hotly anticipated films, and expected to give the box office’s final quarter a considerable lift; the first film was the sixth highest-grossing of 2019.

Phillips and Phoenix spoke of their desire to make the sequel feel as fresh and unexpected as the original, and how their means of doing this – by making it a musical – was conceived by the actor in his sleep.

“I had a dream I was performing as Joker doing songs,” said Phoenix, “and I called Todd [Phillips] because I thought there might be something there.”

The director ran with the idea, he said, because he knew he needed a concept that “had to scare [Phoenix] in the same way the first one did. It had to feel audacious and that we were really swinging for the fences with something different.”

Gaga said she signed on for the sequel because she had been so “deeply moved” by the original. “I loved it so much,” she said. “Sometimes when stories are told about people who are misunderstood by society [you get] a chance to have a hard look at that world. It was something I had never seen before.”

Related: Joaquin Phoenix exits Todd Haynes gay drama five days before filming begins

She praised the film’s “extremely nuanced” approach to music, which sees both leads belt out great American classics when their own words fail them. “We worked really hard on the way we sang,” she said, “unlearning technique and forgetting how to breathe.”

Phoenix reported that he was initially appalled by the idea of singing live, but eventually embraced the experience.

Phillips dismissed the idea that the sequel was conceived in part as a rebuttal to what he felt were “undeserved” accusations that the original glorified violence. “Movies are way too hard to make as a statement in response to something,” he said.

The film opens in the UK and US on 4 October.