The Oscar-winning filmmaker has disclosed that it will “unfreeze” the characters from the first film and deal equally with what they have been doing for the past 20 years.
Ahead of the world premiere of T2 in Edinburgh next weekend, Boyle said it would also look at the “terrifying” process of aging.
Screenwriter John Hodge, who adapted Irvine Welsh’s best-seller for the 1996 original, said the new movie would also look at how employment had become less secure and corporations even more powerful over the past two decades.
He said the film had become “more topical” since Ewan McGregor, Robert Carlyle, Jonny Lee Miller and Ewen Bremner agreed to reunite with Boyle for a sequel.
Meanwhile McGregor has described Trainspotting as “the Oasis of the film world” and said he had been “so upset” after watching a documentary about the band, which broke up after a bitter split between brothers Noel and Liam Gallagher.
Boyle and Hodge – who were interviewed in the LA Times – started working with Welsh on a sequel three years ago after the director and McGregor resolved their much-publicised differences after the actor was dropped from The Beach.
The sequel will follow events after McGregor’s character Renton returns to Edinburgh for the first time in 20 years since, at the end of the first film, betraying his friends by stealing £16,000 they had made on a drug deal and fleeing to Amsterdam.
Boyle said: “In practice, I knew if the script didn’t deal with them equally, like the first one, they wouldn’t do it.
“So then we had to come up with a movie that did that and also wasn’t ... bad. Then there’s the prism of aging, which is terrifying for a lot of us but really terrifying for actors. You remember them frozen in time and suddenly they’re in the present.
“When we first started making this film, I thought the subject was time. And that the reason we didn’t make it ten years ago is because the actors didn’t look like they’d aged enough. Or I wasn’t old enough.
“And I realised after making this film it isn’t about time – it’s about masculinity, about disappointed masculinity. When we made the first film, everyone said it was about drugs, and I said it was about friendship. But I realise now it was really about boyhood. And this is about manhood.
“Movies have this weird Hollywoodising effect, this glamorising effect, even gritty films like Trainspotting.
“It makes people desirable by freezing them. And if you’re lucky, as we were, you get a chance to unfreeze them – sometimes literally, even, by dropping pieces of the first movie in. You get the past and present simultaneously. And that’s a rare, powerful thing.”
Hodge said: “What are these guys like 20 years on? We change a lot over 20 years, but bits of us remain the same. I think the fact that so much time had passed also liberates the movie. If it was just five years later, we’d just expect more of the same – they’re just going to rob a casino in Monaco. Now, people expect things to be different, for a lot of life to be lived.
“We saw an opportunity there – to show how consumer culture has been inflated and employment is less secure and corporations even more powerful. It’s become more topical since we started writing it.”
McGregor said he had been “slayed” by the Oasis documentary Supersonic when he watched it shortly after filming had wrapped on T2.
He said: “I can’t describe it, I was so upset afterwards. Because I was such a huge Oasis fan. Like, ridiculous, a schoolboy fanaticism, when I was a dad already, you know? Embarrassing. And watching that film, I really wanted to go back. Just being out there and having a great time, and being a part of what the 90s has become in my mind.”