Tom Shadyac had it all and was living the dream. Or at least that is what people in Hollywood told him. He was a hugely successful movie director with a string of comedy hits. He had earned himself millions of dollars and had an A-list lifestyle with all the trappings of excess.

Then, in 2007, an already disillusioned Shadyac had a bike accident and became gripped by a profoundly non-showbiz desire: to give his wealth away. Several years later, he has swapped his luxury jetsetting for economy class and his 17,000-square ft mansion in Los Angeles for a trailer park in Malibu.

He has not, however, stopped making films – even if his new one couldn't be more different from the goofball comedies of his big box office days. I Am, coming out in the United States next month, is a documentary that explores not only Shadyac's remarkable journey from riches to rags but the world's ever-growing addiction to materialism.

"I really did not want to die with this conversation buried inside of me," he told the Observer, citing his cycling crash in Virginia as the trigger for his radical turnaround. For months after the fall from his bike Shadyac was ill, suffering debilitating headaches and an acute sensitivity to light and noise that saw him shut himself away in darkness and quiet. It was then that he knew he had to delve deeper into the new life journey he felt he was on. "I had been shifting my life already but the bike accident really made me want to make the film," he said.

In I Am, Shadyac embarks on a journey to talk to world figures who inspired him. He ends up interviewing a list of top scientists, religious leaders and philosophers that includes Archbishop Desmond Tutu, Noam Chomsky and leftwing historian Howard Zinn. About as far from previous hits such as Jim Carrey classics Ace Ventura and Liar, Liar, the documentary is already creating a buzz in film festivals and special screenings at colleges. He has no regrets.

"I didn't like the values that I saw. I was part of the problem and I wanted to stop the hypocrisy. I did not want to preach about the gap between the poor and rich when I represented that gap," said Shadyac, 52, who gave his fortune away to a variety of good causes.

The movie is ambitious in its aims, setting out to explore the notion that our economy and way of life are based on selfish materialism that actually go against our true nature, which is to co-operate and unite. These are themes he explores with Chomsky and Tutu as well as lesser-known figures like author Lynne McTaggart and environmentalist David Suzuki. Shadyac examines the common ground between science and forms of spirituality and examines new discoveries in both areas.

He wants people who watch the film to come away with a changed view of the world and a belief that the power to alter things lies in their own hands. Shadyac points out that Al Gore's climate change film An Inconvenient Truth had similarly humble beginnings but became globally influential. "There has to be a change. I want to be the straw on the camel's back. An Inconvenient Truth caught a zeitgeist and I think I Am can catch a zeitgeist too. It has to," he said.

If the reactions of audiences so far are any indication, then Shadyac could be on to something. He has been taking I Am to colleges and small film festivals giving after-show talks and dealing with packed crowds. "The reaction has been incredible. At our very first screening we got a 20-minute standing ovation. I am not joking," he said. While Shadyac has various plans for his future – more documentaries or perhaps hosting a television show tackling the issues raised in I Am – he is sure of one thing: he will stick to his new values and not become rich again, no matter how well his films do.

He remembers with a shudder the huge amounts of money that flowed into his life after Liar, Liar hit cinema screens. "I thought: 'This is wrong.' It was disconnecting me with art," he said. He said he now saw no difference between himself as a director and anyone else working on his films. "I am not more valuable than a cook on set or the guy who lays the cables. The person cleaning the set is just as valuable to the art," he said.

Those are the sort of egalitarian sentiments that many big names in Hollywood occasionally voice. But Shadyac has lived up to them and is not looking back with envy at his old days of luxury and glamour. "I definitely was not as happy as I am now," he said.