For the past 15 years, Mexican director Alejandro González Iñárritu has been one of his country’s most prominent cultural ambassadors, so it’s hardly surprising when he gives his own national traits a touch of hard sell. Sitting in a London hotel lounge just before Christmas, he explains the emotional intensity that characterises his films: “When I talk about sad things, I talk about sad things. If I give you a chilaquile [a dish made from corn tortillas], it’s a chilaquile. Are you gonna say, ‘Oh my God, it’s a little bit too heavy!?’ It’s a fucking chilaquile, what do you want!?” he roars, beaming.

With a habit of peppering his comments with booming expletives, the 52-year-old former radio DJ is voluble and enthusiastic. As his energetic, expansive presence suggests, the piratically goateed González Iñárritu is no gently contemplative chamber-drama auteur. From the start, the director – who these days shortens his on-screen credit to the more Anglo-friendly Alejandro G Iñárritu – has been noted for his films’ ambition and ferocious energy. His 2000 debut, Amores Perros, was a confrontational mix of domestic melodrama and crime story, involving star-crossed teenage love, multiple car pile-ups and brutally realistic glimpses of Mexico City’s dog-fighting underworld. Similarly kinetic, but in a very different vein, 2015’s Oscar-winning Birdman dazzled with its mix of backstage comedy and long takes, stitched into one seamlessly continuous rush of action.

My duty is to make probable the improbable. If I tell you how I did it, I will ruin your experience

But in terms of going big, Iñárritu has outdone himself with his new film, The Revenant. Based on a true story, via a novel by Michael Punke, and set in a snowbound North American terrain in the 1820s, it stars Leonardo DiCaprio as fur trapper Hugh Glass, who is mauled almost to death by a grizzly bear, then struggles back to life to pursue the man who left him for dead and killed his son. The film comes across as the ultimate Outward Bound adventure, a hard-bitten (not to say frostbitten) tale of vengeance. But for Iñárritu, The Revenant is really a spiritual drama, a story of survival and transcendence. “The whole journey for me,” he says, “was this guy remembering. The word ‘remembering’ comes from the members – you lose a member of your family, you lose a member of your body, your hair, your teeth. He’s stitching his members back. He’s remembering himself and coming back alive, healing, being reborn again.”

Iñarritu sees Hugh Glass as becoming “a man, a beast, a saint, a martyr, a spirit”. The director, who meditates regularly, says he isn’t religious, but has long been concerned with matters metaphysical: the title of his 2004 film 21 Grams refers to the hypothetical weight of the soul. “I’m not any more a practitioner of Catholicism, but I was obviously interested in that saint spirit – I really truly believe that it’s much more real than physicality.”

Leonardo DiCaprio and Tom Hardy star in The Revenant – video Guardian

But the physicality of The Revenant is real enough, the film emerging from an exceptionally – indeed, notoriously – arduous shoot. Iñarritu and his crew, including Mexican cinematographer Emmanuel Lubezki, the wizard behind the visual athletics of Birdman, filmed for nine months in British Columbia and Alberta, in remote locations that took two hours to drive to daily, with temperatures dropping as low as -40C. The story was filmed chronologically, using only natural light, often, like Birdman, in exceptionally long unbroken takes, and with shooting windows of only two hours’ adequate sunlight each day. The whole production was distinguished by an insistence on doing things for real, on working in conditions not so different from those faced by the drama’s characters. “A film like this,” Iñárritu says, “is a homage to the original cinema tradition, where the directors went to the places, and you risked challenges. I passionately believe that that should be an example of how film should be committed.”

The approach is a seemingly perverse anomaly in this day and age. In the pre-digital era, it made some sort of sense that Werner Herzog would make the grandly quixotic flourish of having a real ship hauled over a hill in his Fitzcarraldo (1982); today it seems patently crazy that, instead of taking the standard Hollywood approach and commissioning a computer-generated avalanche for one scene, Iñárritu actually engineered a real one.

He cites favourite man-against-nature films that emerged from similar challenges: as well as Herzog’s films, Tarkovsky’s medieval epic Andrei Rublev, Kurosawa’s Siberian tale Dersu Uzala, Coppola’s Apocalypse Now. The difference between doing it for real and resorting to electronic fakery, Iñarritu says, is like that between organic produce and GM food. “The avalanche, you can do it digital, but I swear, but if you put it back to back…” – he extends his arms and does a little mime of someone comparing avalanches. “We have lost the taste for the real. I went with my family to Peru last year, to Cusco, and there’s this kind of corn that they sell in the street. I tasted one of those corns and I almost cried, because it reminded me when I was a kid, how it tasted in Mexico. When I go to Mexico and I taste a mango on the beach, it’s like… what the fuck!? When you taste a mango in the United States, it’s just tasteless.”

Nevertheless, it should be noted that The Revenant’s ravening bear, as is now a matter of record, is entirely CGI – and the most viscerally realistic form of artificial animal life that the technology has yet created. But today Iñárritu declines to discuss his methods. “My duty is to make probable the improbable,” he says, with an impish smile. “If I tell you how I did it, I will ruin your experience.”

Leonardo DiCaprio certainly rises to the challenge of his role with gusto. Apart from growing a vast, unkempt beard (which ended up, according to rumour, crawling with fleas), he studied two Native American languages and ancient healing techniques, immersed himself in rivers at sub-zero temperatures, and – can this possibly be true? – ate raw bison liver.

“He did. He did!” Iñárritu chuckles. “That liver is real.”

He also climbed inside a dead horse?

Gael García Bernal in Alejandro González Iñárritu’s first feature film, Amores Perros. Photograph: Optimum/Sportsphoto Ltd/Allstar

“Yeah,” says Iñárritu, grinning a touch cagily. “We did some things, but yeah. That was not fully true. It is, but it’s not.” Meaning? “Meaning that’s an illusion which I will allow you to get into.”

I wonder how you persuade a top Hollywood star to do this kind of stuff; presumably it doesn’t just happen spontaneously. Did Iñárritu have to negotiate? Was there a bison liver clause in DiCaprio’s contract? (In fact, after our interview, an article in Variety reveals that the actor was presented with fake offal, but didn’t find it convincing. It was decided that he would chomp on the real thing – once his lawyer and agents had been consulted. “The bad part is the membrane around it,” DiCaprio commented. “It’s like a balloon.”)

“I have never had such an easy relationship with somebody,” Iñarritu says of his star, with whom he started discussing the project well before making Birdman. “He couldn’t be more brave or more collaborative, and even encouraged me to do more things. I didn’t have to convince him at all. I even had to prevent him sometimes.”

Iñárritu makes the shoot sound like a cheerfully boisterous affair, but stories started to circulate during production that this expedition belonged in the annals of tough shoots to rank with Apocalypse Now and Erich von Stroheim’s Death Valley trek for his 1924 epic Greed. The initial budget of $60m rose to $90m, then finally $135m, partly because bad weather necessitated an additional leg of shooting in Argentina.

Last July, the Hollywood Reporter ran a story that the shoot was a “living hell”, as one crew member put it; there were accusations of indecision, of feuding between Iñárritu and one of his producers, and of disregard for safety, including the report of one actor being repeatedly dragged naked across ice. In the same publication, Iñárritu dutifully responded to the charges, although sometimes in terms redolent of a certain maestro loftiness. “As a director,” he said, “if I identify a violin that is out of tune, I have to take that from the orchestra” – then concluded, “When you see the film, you will see the scale of it. And you will say, ‘Wow.’” Indeed, whether or not The Revenant attains the deeper existential insights that its director aspires to, it’s undeniable that, as adventure spectacle, the film is often genuinely gasp-inducing.

Coming from a violent country, I don’t find violence funny. Now violence has to stop being fun

When I ask Iñárritu about the controversy, a palpable impatience creeps into his voice. “I have to say, there’s nothing more boring to talk about than the challenges of production. ‘Oh my God, poor guys, they suffered…’ Honestly, who cares? The only reason I answered that is because I was asked, and I said: ‘There’s nothing for me to hide here.’”

The shoot, he insists, “was done with maybe one of the best crews ever. Every single department was taken care of by a specialist of stunts, security, blah, blah. It was even too much security by my standards in Mexico! I was working with the rules of the union, and with super-professional people – every shot that was dangerous, we rehearsed for weeks or months.

“What I’m saying is, every step was super-challenging, it was stressful, the standards I set the film to were absolutely high. When that stress is not for you, I respect that. The ones who stayed, which is 99.9%, we hold a friendship and camaraderie.

“Were we laughing all day? No! We were working like hell to make it happen! It was like Shackleton, when he went to the pole, he said [to his companions], ‘You probably will not return.’ [I said:] ‘These are gonna be the conditions, this is how we’re gonna shoot it.’ No one was hiding the truth.”

Leonardo DiCaprio in The Revenant Photograph: AP

That apart, Iñárritu is more amused than annoyed by pre-release reports that the film showed DiCaprio’s character raped by the bear, a rumour that distributor Fox rushed to deny (the bear is a female guarding her cubs). Then Hollywood blogger Jeffrey Wells caused a stir by announcing that the film’s brutality was strictly for male viewers: “Forget women seeing this.” Not himself a user of social media, Iñárritu shrugs impatiently at online babble culture. “It’s just a cacophony of imbeciles.”

For all its shooting-the-rapids dynamism, The Revenant maintains the kind of seriousness that has long been Iñárritu’s trademark. He has always been a full-blown human condition film-maker, starting with his debut and continuing with follow-ups 21 Grams and Babel, with its international cast including Brad Pitt, Cate Blanchett, Japanese star Rinko Kikuchi and Amores Perros discovery Gael García Bernal. These first three films, collaborations with screenwriter-novelist Guillermo Arriaga, established a distinctively aggressive style of art cinema that made Iñárritu the accessible philosopher-auteur of the millennium. His films were emotionally involving, often spectacular and formally audacious – unabashedly forthright commentaries on the state of society today, stressing that in the globalised world all our fates are interconnected. However, Iñarritu could also be prone to earnestness, as in Biutiful (2010), a laboriously solemn Barcelona-set drama about migrant workers, cancer and the afterlife.

But making bold statements is in keeping with a Mexican “maximalist” tradition, Iñarritu tells me, invoking the epic style of his nation’s most acclaimed artists. “I can’t deny that I come from [José Clemente] Orozco or [David Alfaro] Siqueiros, from these muralists. All these murals of the last days of judgment – there are no nuances!

“We as a culture always grab the most spicy sauce, the most heartbreaking rancheros and boleros music, such dramatic telenovelas and soap operas. All our culture and all the cosmological themes and political themes and social themes and religious themes are always conveyed on these huge canvases, with big colours… [Amores Perros] was an ambitious triptych mural very much in the tradition of my culture – and in that sense, yes, it was like – arrghh!…” he exclaims, clenching his teeth and imitating someone trying to bend an iron bar.

Alejandro González Iñárritu. Photograph: Antonio Olmos/The Observer

Yet Iñárritu has not been a specifically Mexican director for some time. He was one of three world-beating, commercially minded directors who spearheaded a new surge of energy in their nation’s cinema – the others being Alfonso Cuarón (Gravity, Children of Men) and genre specialist Guillermo del Toro (Pan’s Labyrinth, Crimson Peak). None of them now directs at home: the last of Iñárritu’s films to feature Mexican themes was Babel. He has lived in the US for 14 years, moving to Los Angeles with his wife – designer María Eladia Hagerman – and their daughter María and son Eliseo, now 20 and 18 respectively. Their move came after Iñárritu’s parents had both been victims of violent robbery in Mexico City. “My mother was assaulted and beaten, and her teeth were broken. My father was taken for six hours in a trunk – they stole 5,000 pesos,” Iñárritu says with a mirthless laugh. “It’s like literally 50 dollars. It was a very, very scary moment to be there.”

That sort of experience, he says, is one reason he doesn’t enjoy violence on film. Amores Perros is as blood-soaked as any recent crime drama, while The Revenant, rooted in nature, is as grisly as anything you’re likely to see on screen this year. But the latter, he says, uses its horrors in the context of a tale of endurance: “This film has much more nobility, and much more motivation to inspire.” What he objects to is slaughter as entertainment. “Coming from a violent country, I don’t find violence funny. And now that the western world is getting to how it feels in my country, to be vulnerable every moment, now violence has to stop being fun.”

Growing up in Narvarte, a lower-middle-class district of Mexico City, Iñárritu was expelled from school at 17 after dabbling in theft and running off with his girlfriend under the influence of the movie of Hair: “I was hearing Pink Floyd all day and getting stoned. I wanted to be a hippy.” The girl’s father, who was very wealthy, warned Iñárritu Sr that his son should back off or risk a possibly fatal beating. Alejandro made one last tear-filled phone call – “an adolescent heartbreaking love story – ‘Goodbye, I love you’, and that was the end of it.” Soon after, he signed up for the first of two stints working on cargo boats, sailing up the Mississippi, then to Europe and Africa. It would all feed into his film-making, he says, although he only realised this much later. “The funniest thing is, five years ago – only five years ago, I promise you –I suddenly realised that all the films I have done, I did in places where that boat went. The first American film I did, I chose Memphis, Tennessee. Then I did Babel, half of it was in Morocco, then I did one in Barcelona [Biutiful]… Suddenly I said, ‘Wait a minute…’ You can’t imagine how stupid I felt. I thought, my God, it was clear, but I didn’t recognise it. It’s beautiful when you find things like that – you realise creativity doesn’t come from a rational place, it’s subconscious, and you should not be aware.”

I ask how, as the maker of several films about global strife and solidarity, Iñárritu feels about the state of the world at the end of 2015 – particularly about Donald Trump’s proposal, the week of our interview, to ban Muslims from entering the US. As it happens, his thoughts on Trump are well known, and vice versa. When Birdman won four awards including best picture and best director at last January’s Oscars – a year after Alfonso Cuarón’s best director win for Gravity – Trump commented sourly that it had been “a great night for Mexico, as usual”. In November, speaking in Los Angeles, it was apparent whom Iñárritu had in mind when he referred to “constant and relentless xenophobic comments that have been expressed against my Mexican fellows”. Today, however, Iñárritu answers my question by returning to his new film. “The Revenant really addresses a lot of the things I have to say now.” For him, this story of 1820s America is really about the roots of capitalism. “The way these men deal with nature… Cutting trees – profit from it. Killing animals – profit from it. And the impact they had on the [indigenous] communities, the broken promises and contracts and the blindness of seeing them as people, the fear of the otherness, the judgments and the prejudice of the colour of the skin and other cultural beliefs… We haven’t escaped from that kind of fear and prejudice.”

It’s more than likely that early 2016 will again see Iñárritu basking in the awards limelight: The Revenant has four Golden Globe nominations, including best picture, best male performance and best director. But, Iñárritu says, Birdman’s Oscar night victory flight was somewhat lost on him, as he was already shooting The Revenant, and assorted production problems had him constantly checking his emails through the festivities. “The next night I was on the plane, and the next morning I was shooting a huge scene, so I never had that quiet moment with your wife where you sit and you say… [he puts on a lofty “cigar-and-champagne” voice] ‘I won an award!’ It was exhausting. But I have to say, it was the most healthy thing for my ego. To be working in the awards season is a blessing!”

As for what comes next, Iñarritu says he has no plans, but one suspects he’s going to take a break from the great outdoors and nature red in tooth and claw. Now, he says, “My life is claiming me. I want to live – to germinate something, but with quietness, niceness.”

The Revenant opens on 15 January