In the last week of May, two months after showing me the photos, Cheung's physique landed him the cover of the June issue of Chinese magazine . It became a hot topic on social media and invited myriad parodies, digitally manipulated imitations and widespread amazement at how a 45-year-old man could reinvent himself.

Cheung and I met again last Saturday, five days before is set to open in Hong Kong. The unlikely fitness icon is now claiming that he has already lost his six-pack abs and has a body "just like yours and everybody else's". "I've done exactly what I told you then. Dude, I'm not interested in that sort of thing," he says of body building. "When it comes to exercise like running and boxing, I'm happy to do those. And yet, if not for the making of , I don't think I would have the urge or determination to build up a body like I did."

When I tell Cheung that his feat is all the more impressive because he was not a gym rat to start with, he sighs and says nothing.

The actor's extreme dietary programme for has been widely reported. The first phase saw him cut out oil, salt, sugar and carbohydrates from his daily intake, while the second required him to eat between 20 to 30 egg whites a day to go with the training. Cheung spent three days eating only white rice to expand his muscles. He also let his body dramatically dehydrate to highlight its streaks during filming.

"I couldn't even eat with my family," Cheung says. "I couldn't. I just stared at their food with hatred. Every day my food consisted of the chicken meat we bought at supermarkets. It's boiled, shredded and then mixed with unflavoured soy bean milk. I literally drank the meat. I didn't eat meat because I just couldn't do it. It tasted like the leftovers you feed farm pigs. I just had to stop thinking and force myself to swallow it."

If he had kept going, would it have lead to anorexia?

"That would have lead to death," the actor deadpans, before repeating the word "death" three times.

By now, however, no one could say his suffering was not at least partly worth it. Judging by the overwhelming admiration that Cheung has attracted, the best actor award he collected at the Shanghai International Film Festival in June for the role is almost looking like an afterthought by comparison.

"To be honest, it was never a calculated move to wow the public just so I can get excited about myself," says Cheung. "I did it purely because I wanted to do my best for this job. But at the same time, after people saw this body, it has made some citizens realise: if Cheung Ka-fai can have this body because of his determination, so can I. It has become a kind of 'Cheung Ka-fai inspiration', and this impact has made me realise that I can also make some positive contribution to society. To me, that was unexpected."

For many of his long-term fans, Cheung's own transformation as an actor may have been the most astonishing development of all. It was only a few years ago that he looked like succeeding Stephen Chow Sing-chi as the king of Hong Kong comedy. But Cheung was not content with merely playing everyone's favourite clown in director Wong Jing's gambling comedies, such as the profitable series from the late 1990s and early 2000s.

Determined to be taken seriously as an actor, Cheung appeared in four crime dramas by auteur Johnnie To between 2004 and 2006: , the two films, and . It was when he reunited with Dante Lam, with whom he first collaborated on 2001's , that Cheung found his career breakthrough with the lauded role in , playing a former boxer-turned-assassin who's losing his eyesight.

According to Cheung, marks a new direction in the duo's long-time collaboration: it is neither a cops and robbers romp nor a bleak and violent look at the dark side of humanity. The one aspect it doesn't break away from? The alarmingly high probability that Cheung is playing an ex-con in his recent films, from to , (2009) and all the way back to .

"I've been wondering about this too," says Cheung. "I was asked about this by a friend recently, and I didn't know how to make sense of it. [It may be down to] the fact that I never really thought about how one character of mine relates to the others. When I take a role, I always start from scratch."

The makeover from prominent comedian to A-list actor of dramatic roles over the past decade, he says, has had its obstacles.

"It's not easy to get the world to accommodate your decisions," he says. "So what if you want to do a serious drama today? Or a comedy tomorrow? Or play a mental patient or star in a ghost film the day after? This is not a perfect world and it doesn't revolve around you. It took effort in pulling off my transformation. I spent four or five years letting people know that I wanted to be in dramas [instead of comedies]."

Considering the number of dramatic projects that he has lined up for the rest of this year, Cheung's metamorphosis looks close to completion. After , he will appear alongside Louis Koo Tin-lok and Lau Ching-wan in Benny Chan Muk-sing's , reunite with Dante Lam for the cop thriller , take the lead role in his own Malaysia-set directorial effort , and start filming , to be helmed by co-directors Longman Leung Lok-man and Sunny Luk Kim-ching.

Cheung plans to take a short break from acting after wrapping up in November. When asked about the chances of an sequel, he offers instead an easier way out: "I say, let's do a prequel so that I don't have to build up a body like this again. After all, I'm not a professional athlete. I wouldn't dare to do it again. The discipline and self-control involved … it's hard for anyone else to understand."

Cheung aficionados will remember that the actor said pretty much the same thing after his intense preparation for back in 2012. Some things never change.

Unbeatable